|Photo courtesy of Anan Interpretive Staff, Tongass National Forest|
18 July 2013: DeGraaf, Richard M.; Rudis, Deborah D. 2001 citation corrected to DeGraaf, Richard M.; Yamasaki, Mariko. 2001.
Ursus amblyceps Baird =
Ursus americanus amblyceps Baird
Ursus americanus Pallas
Ursus (Eurarctos) americanus sornborgeri Bangs
Ursus arctos schwenki Shoemaker
Euarctos randi Anderson
Eurarctos hunteri Anderson =
Ursus americanus americanus Pallas
Ursus califoriensis J. Miller =
Ursus americanus califoriensis J. Miller
Ursus (Eurarctos) carlottae Osgood =
Ursus americanus carlottae Osgood
Ursus americanus var. cinnamomum Audubon and Bachman =
Ursus americanus cinnamomum Audubon and Bachman
Ursus americanus var. emmonsii Dall
Ursus glacilis Kells =
Ursus americanus emmonsii Dall
Ursus floridanus Merriam =
Ursus americanus floridanus Merriam
Ursus kermodei Hornaday =
Ursus americanus kermodei Hornaday
Ursus luteolus Griffith =
Ursus americanus luteolus Griffith
Ursus machetes Elliot =
Ursus americanus machetes Elliot
Ursus americanus kenaiensis J.A. Allen =
Ursus americanus perniger J.A. Allen [83,276]
Other subspecies of American black bear within the same range as the Louisiana black bear are listed as having a "similarity of appearance to a threatened taxon". This includes all counties of Louisiana, Mississippi, and Texas, and the historic county range of the Louisiana black bear .OTHER STATUS:
American black bears are present but uncommon in northern Mexico [20,63,132,203]. NatureServe provides a distributional map for the American black bear in Canada and the United States.
The distribution of each American black bear subspecies is listed below [83,281]:Ursus americanus altifrontalis - Pacific Northwest Coast from central British Columbia through northern California and inland to northern Idaho and British Columbia
|Photo courtesy of Ana Interpretive Staff, Tongass National Forest|
Mating: American black bears have low reproductive rates [76,114]. Mating occurs from late May to August and peaks in June [76,114,132,208,272]. Females typically mate for the first time at 3 years old [64,272] but may not mate until 8 years old in northern portions of their range [41,114,131]. Females that have borne young usually breed every other year [76,114,131]. If females abandon their cubs after den emergence in spring, they may breed again in early summer of the same year .
Reproductive success: Female reproductive success may be determined by diet and nutrition. During years of high mast production, good nutritional condition of American black bears resulted in earlier maturation, larger litter sizes, shorter breeding intervals, and higher survival rates [25,43,48,64,76,114,131,208,209,213,226]. For example, over a 6-year study period, 26 of 28 female American black bears in western Massachusetts produced cubs when they had consumed a high fat and high carbohydrate diet of hard and soft mast. During years of low mast production, 10 of 10 females produced no cubs . In some studies, variability in food supply did not solely explain fluctuations in reproduction [44,118,172].
Gestation period and litter size: Due to delayed implantation, embryos are not implanted and cubs are not born until the winter denning period [76,78,272]. Litter size ranges from 1 to 5 cubs [76,132,272], depending on the age and nutritional condition of the female before the denning period . Litters typically consist of twins or triplets . Subadult (1.5-3 years old) females produce the smallest litters (typically 1 cub) their first time breeding , and older females produce intermediate-sized litters [76,132]. Mean litter size was 1.6 cubs in the Shasta-Trinity National Forest, California (n=6 adult females) , Sequoia National Park, California (n=9 adult females) , and the Whitefish Range in northwestern Montana (n=45 adult females) . Mean litter sizes were 2.25 (n=20) and 1.41 (n=17) in the Ouachita Mountains and Ozark Mountains of Arkansas, respectively . Mean litter size in northeastern Minnesota was 2.38 cubs (n=52 adult females) . In northern Coahuila, Mexico, mean litter size was 2.75 cubs (n=12 adult females) . Sex ratio of cubs may be determined by maternal condition. In La Mauricie National Park, Quebec, females gave birth to more males when maternal weight was heavier .
Development: A mother's milk supply depends on the quality of nutrients obtained the year before she gives birth . Large, well-nourished females produce healthier cubs than malnourished females . American black bears in eastern deciduous forests generally experience higher growth rates than those in western North America due to a larger variety of foods, including oak (Quercus spp.) acorns . After leaving the den, cubs gain weight quickly if abundant food is available . Young are weaned approximately 7 months after birth, between July and September [76,114]. In northern portions of the American black bear's range, where summers are shorter and food is less abundant, females may wean at a later date . Young remain with their mothers until they are approximately 1.5 years old, and/or when their mothers enter estrus [76,114,149,208,208,227].
Social organization: American black bears are generally solitary. Exceptions occur during the breeding season, the first 1.5 years of a cub's life [78,114,132,208,272], and areas where American black bears congregate to forage on seasonally abundant foods [132,208,213].
Habits: American black bears are diurnal [9,41,74,142,149] but may be nocturnal in areas containing human food sources such as garbage dumps, agricultural areas , or in habitat cooccupied with grizzly bears (Ursus arctos horribilis) . During early spring and late fall, females are more nocturnal than males. They forage nocturnally to improve physical condition needed for breeding, denning, and lactation .
Mortality: Starvation is the most significant cause of natural mortality [76,114,213,221], especially in northern latitudes where foraging periods are shorter . Mortality rates may range from 5% when food is abundant to 70% when food is scarce . Natural mortality is high between birth and 2 years of age and depends primarily on food availability [76,213,221], physical condition of the mother, litter size, and/or experience of the mother . Mortality is also high for subadult males (>2 years old) during dispersal from natal areas because subadult males may be forced into less preferred habitat by older American black bears . After home ranges are established, mortality for males and females is 5% to 10%/year . Other causes of natural mortality include disease, predation, injuries from other American black bears, and cannibalism [76,114].
Human-related mortality for American black bears is caused by hunting, collisions with vehicles, and poaching. Hunting-related mortality for subadult males is greatest during dispersal from natal areas [64,114,146,227]. Mortality from humans is greater during seasons or years when natural food resources are low and American black bears enter human-inhabited areas looking for food [169,213,221,255].
Survival rates: In the Ouachita Mountains, Arkansas, mean annual survival rates of males and females over a 2-year period was 94% for American black bears >1 year old and 88% for cubs. In the Ozark Mountains, Arkansas, mean annual survival rates were 0.87 for males and females >1 year old, and 0.25 for cubs . In northeastern Minnesota, the cub survival rate ranged from 59% to 88%, depending on food supply during year of conception and year of birth . In the Pisgah Bear Sanctuary in North Carolina, the mean annual survival rate of male and female American black bears trapped 251 times over a 15-year period was 76% (SD= 0.04, n=151) .
Dispersal: Natal dispersal occurs in the subadult age class and is male-biased [64,114,146,208,223,227]. Typically, >95% of subadult females establish home ranges within their mothers' home ranges [64,146,227] (see Home range and density). In areas of high American black bear densities or limited food resources, adult females may prompt subadult females to disperse [25,114]. Dispersal distance of 18 subadult males in northeastern Minnesota ranged from 8 to 136 miles (13-219 km) and averaged 38 miles (61 km) . Dispersal distance for 57 yearling to 3-year-old males in western Virginia ranged from 0.6 to 49.7 miles (0.9-80.0 km) and averaged 8 miles (13 km) .
Denning: American black bears den to conserve energy during winter months [148,224]. The denning period depends on length of winter [132,148,228] but typically occurs from October to May [9,41,73,148]. In southern latitudes, American black bears typically den for 3 months (January or February to March or April), but not all American black bears den [63,89,102,175,186].
Onset of denning may be related to sex, reproductive status, food availability [73,114,117,224], and/or weather [114,148,224,228]. Females typically enter dens earlier and leave dens later than males [54,73,148]. In the northeastern Cascade Range of Washington, females entered dens approximately 1 week earlier in the fall and left dens 1 week later in the spring than males . Pregnant females den longer than nonpregnant females or males [54,148,208,224,228]. A pregnant female in south-central Alaska spent 247 days in her den . In southern portions of the American black bear's range, subadult and adult males and nonpregnant females may not hibernate . In Coahuila, Mexico, all pregnant females (n=13) denned, 2 of 5 females with yearlings denned, and 0 males (n=10) denned .
American black bears may enter dens early and emerge from dens late when food is scarce [117,132]. Otherwise, a negative energy balance may occur if they continue to forage as food becomes less abundant . Acorn crop failure may influence denning behavior. During a gypsy moth infestation that destroyed the acorn crop in Shenandoah National Park, Virginia, pregnant American black bears entered dens an average of 1 week earlier and emerged from dens 1 week later than other females .
Secure den sites ensure survival [54,101,186]. Den selection may be influenced by factors including availability of dens, climate, reproductive status, age of the American black bear, energetic efficiency of the den, and/or safety from predators [54,56,73,76,186,224]. Den type varies geographically; however, dens located in dead- and live-tree cavities are preferred across the American black bear's range [35,36,114,133,189,234]. In northern latitudes, den sites may be located in hollow trees and logs, under fallen logs or piles of man-made debris, under tree roots, in trees with hollow chambers at their bases [36,54], or in rock crevices . In southern portions of the American black bear range, dens may consist of open nests of leaves and grass, shallow depressions on the ground [89,132], or may be elevated in hollow trees, especially in areas where seasonal flooding may occur [186,273]. In second-growth forests that lack large tree cavities, caves, slash piles, rock crevices, or nests on the ground surface may be used for den sites [114,208]. Dens with large chambers may be an important factor in den selection for pregnant females and for old, large American black bears [54,129]. In western Virginia, American black bears >10 years old used rock cavities more often than trees, probably because they could not find big enough tree cavities . American black bears on Vancouver Island denned close to spring forage areas to decrease long movements and encounters with other American black bears . Dens may or may not be reused [24,54,114,117,129,208,228]. Den reuse may be related to the longevity of den structures  or availability of suitable den sites . For detailed information about habitat used for denning in various geographic locations, see Preferred Habitat.PREFERRED HABITAT:
Habitat use is dictated by seasonal food production [9,96,114,208]. In general, meadows are preferred for foraging on grasses and forbs during spring [76,114,248,261]. Riparian habitat, avalanche chutes, and early-successional habitat created by logging or fire are preferred for foraging during summer [72,86,92], and mature forest containing hard mast is preferred during fall [64,150,208,208,221,222,264,268] (see Food Habits). For denning and cover, mature or old-growth forest containing coarse woody debris, snags, and adequate cover are typically preferred [35,54,193,204,261] (see Stand- and landscape-level habitat and Snags and coarse woody debris).
Stand- and landscape-level habitat:
Canada—On the coast of British Columbia, American black bears prefer midelevation habitat, late-successional forest, and forest patches with high structural complexity and coarse woody debris. In the Nimpkish Valley of Vancouver Island, American black bears denned exclusively in structures of wood on slopes >15%. Of 67 American black bear dens, large-diameter (x= 56 inches (143 cm) DBH)) hollow trees were used most often, followed by root boles, stumps, logs, and under trees. Western redcedar (Thuja plicata) and Alaska-cedar (Chamaecyparis nootkatensis) were used most often (28% and 30% of dens, respectively), because they tend to decay in the heartwood but retain a hard outer shell, providing good thermal and security cover. Some dens were located 52 feet (16 m) above ground, and those that required entrance from the tops of hollow trees provided the most security. The following table shows tree species and diameters of den types used by the American black bear :
|Tree species and mean diameters of American black bear dens in the Nimpkish Valley, Vancouver, 1993-1995 |
|Den type (number of dens)|
|Tree species||Hollow tree (n)||Log (n)||Root bole (n)||Stump (n)||Under tree (n)||Mean diameter inches (cm)||SE||n, total|
|Western redcedar||14||1||4||0||0||61 (155)||14||19|
|Western hemlock (Tsuga heterophylla)||3||0||2||2||2||55 (139)||16||9|
|Douglas-fir (Pseudotsuga menziesii)||0||3||5||0||0||45 (115)||13||8|
|Pacific silver fir (Abies amabilis)||0||0||0||2||0||55||15||2|
|Sitka spruce (Picea sitchensis)||0||0||0||2||0||75 (190)||9||2|
|Mountain hemlock (T. mertensiana)||0||0||0||0||1||53 (135)||0||1|
Of 185 visual observations of American black bears on the northeastern coast of Labrador, "forested" habitat was used most often (53.8% of observations). "Forested" habitat consisted of 3-foot (1 m)- tall spruce/fir; black spruce (Picea mariana)/lichen; birch (Betula spp.) thickets; dwarf shrubs; and tuckamore (spruce trees stunted from coastal salt spray). Barren grounds, which consisted of any nonwetland area with <5% canopy cover, were used nearly as much as forest (40.4% of observations). Of 18 den sites found, 7 were located in forest, 6 were in barren grounds, and 5 were in shrub thickets. Because large, hollow trees were uncommon in the area, all dens were excavated and den roofs were supported by root systems of woody vegetation .
In British Columbia, American black bears use Oregon white oak (Q. garryana) for foraging, thermal, and security cover .
Alaska—In the Yukon-Tanana uplands of interior Alaska, preferred spring forage areas were riverbottoms containing brush ≥2.5 feet (0.8 m) tall and paper birch (Betula papyrifera), quaking aspen (Populus tremuloides), and black cottonwood (P. balsamifera ssp. trichocarpa). Riverbottoms contained new green leaves and abundant horsetail (Equisetum spp.), which composed 86% of their spring diet. During summer, American black bears preferred foraging for bog blueberries (Vaccinium uliginosum) in "old" burns (age not given) dominated by willow (Salix spp.), alder (Alnus spp.), and dwarf birch (B. nana) .
Den site selection and den type were related to topography and climatic conditions in south-central Alaska. On the Kenai Peninsula, American black bears denned in 2 major vegetation types: "regrowth" boreal upland forest (67% of dens, "regrowth" not defined ) and "mature" boreal upland forest (31% of dens, "mature" not defined). At high elevations of the Kenai Peninsula and the Susitna River Basin, caves and excavated dens under large boulders and rockpiles were used most often because few trees attained large diameters. In virgin coastal rain forest at low elevations of the Kenai Peninsula, large-diameter western hemlock, white spruce (Picea glauca), and black spruce were preferred for denning. At low elevations in the Susitna River Basin, American black bears preferred denning in alder draws with spruce or paper birch. In Prince William Sound, excavated dens at low elevations were more prone to flooding at low altitudes and were not used as often as tree dens or rock caves .
In southeastern Alaska, American black bears preferred den sites located in windstorm-protected forest (58%) over windstorm-prone forest (6%). In windstorm-protected forest, large, hollow trees (>35 inches (88 cm)) were least prone to wind damage. Density of large trees was twice that of the windstorm-prone forest and the forest was in later successional stages .
Pacific Northwest—On Long Island, Washington, yearling and adult male and female American black bears selected habitat within home ranges disproportionately to availability, preferring recently logged areas over older logged areas. Preference was probably related to availability of berries and cover. Habitat consisted of forest formerly dominated by Sitka spruce. In recently logged areas (7 to 14 years old), shrub cover was 56%. Dominant shrubs were salal (Gaultheria shallon), red huckleberry (Vaccinium parvifolium), and evergreen huckleberry (V. ovatum). Berry-producing shrubs were 7 to 8 times more abundant in the recently logged areas than in older areas. Young western hemlock was the most dominant tree species, and cover was 7%. In intermediate-aged logged areas (14 to 20 years old), shrub cover was 21%. Young western hemlock occurred in small, dense stands, and cover was 58%. These areas provided adequate cover and food for American black bear, but not as much food as recently logged habitat. In the oldest logged areas (≥37 years old) and in alder stands, shrub cover was 7% to 8%. These areas were dominated by western hemlock and used least often. Mature timber (age not given) stands were dominated by western redcedar and covered 346 acres (140 ha) of the island. Shrub cover was 45%. Tidelands were associated principally with slough systems and contained various sedges (Carex spp.), rushes (Scirpus spp.), and halophytic forbs. Edges (115 feet (35 m)) between 2 vegetation types) occurred between areas used for foraging and for cover and were often used in all ages of habitat .
|American black bear use of habitat on Long Island, Washington |
|Habitat||% cover on island||% cover on American black bear home ranges||% American black bear locations in habitat types (n=1,973 locations)||% locations on edges|
|7- to 14-year-old logged||28||36||26||23|
|14- to 20-year-old logged||22||22||35||16|
On the Willamette National Forest, Oregon, female American black bears preferred early-successional habitat for foraging and late-successional habitat for cover and denning. Adjacency of early-successional stages (shrub and sapling-pole) to mature forest was also preferred. Habitat was dominated by Douglas-fir on dry, low-elevation sites; western hemlock on moist, low elevation sites; and Pacific silver fir, Douglas-fir, western hemlock, and mountain hemlock on high-elevation sites. Open-canopy sapling/pole habitat (canopy closure <60%; shrub understory common) was preferred for foraging during summer. Open-canopy mature timber (canopy closure <80%; average tree DBH >21 inches (53 cm); understory of shrubs and small trees common) and closed-canopy mature timber (canopy closure 80% to 100%; average tree DBH >21 inches; some ground vegetation) were preferred for cover and denning. During fall, open- and closed-canopy mature stands with steep slopes and southeastern exposures at low-elevations were preferred for foraging and hiding from hunters. American black bears were negatively associated with roads and positively associated with riparian habitat .
In the Blue Mountains of northeastern Oregon, American black bears used large-diameter (>40 inches (102 cm)) hollow western larch (Larix occidentalis) and grand fir (Abies grandis) trees located within old-growth forest for denning. Of 59 American black bear den locations, 41% occurred inside hollow trees that were either standing or lying on the ground. American black bears entered 42% of standing hollow trees from the tops or near the tops of trees, which offered the best protection from predators. These trees averaged 45 inches (114 cm) DBH (range 36-63 inches (91-160 cm)) and 62 feet (19 m) tall (range 26-98 feet (8-30 m)). Den entrances averaged 43 feet (13 m) above the ground . Other trees used by American black bears in the Columbia River Basin region for denning and resting include white fir (A. concolor) , western redcedar, and subalpine fir (A. lasiocarpa) .
Due to the dry climate in the northeastern Cascade Range, American black bears prefer riparian and deciduous forest for foraging. In the Okanogan National Forest, Washington, American black bears preferred the following habitats for home ranges (in decreasing order): deciduous forest, Douglas-fir forest, riparian forest, meadow, subalpine fir forest, shrubfield, mosaic (mixture of trees, shrubs, forbs, and bare ground), mosaic-harvest, bare, ponderosa pine (Pinus ponderosa) forest, other conifer forest, shrub-steppe, postfire meadow, and western hemlock forest. Within home ranges, American black bears selected for a mosaic of food resources and cover in forested habitat classes. Preferred home range habitat was (in decreasing order): riparian forest, ponderosa pine forest equal to Douglas-fir forest, meadow, hemlock forest equal to subalpine fir forest, other conifers, shrubfield equal to mosaic, mosaic-harvest, shrub-steppe, and meadow-fire areas .
California—In forests dominated by Douglas-fir on the Six Rivers, Klamath, and Shasta-Trinity National Forests, mean relative abundance of American black bears was greatest in late-successional stages and lowest in intermediate successional stages :
|Mean relative abundance of American black bears among successional stages in Douglas-fir forest |
|Successional stage||American black bears captured (n)|
|Early (trees <10 years old)||20|
|Sapling (10-20 years old)||25|
|Pole (20-50 years old)||5|
|Sawtimber (50-150 years old)||42|
|Mature (150-250 years old)||45|
|Old growth (>250 years old)||48|
|Total number captured in all habitats||196|
Southwest—During spring in southwestern Colorado, American black bears prefer foraging in mixed-shrub and Gambel oak (Q. gambelii) habitats. During summer, late-seral Gambel oak, mixed shrub, ponderosa pine-Gambel oak, quaking aspen, and riparian habitats containing abundant berry-producing plants are preferred. During fall, American black bears move to low elevations seeking hard mast such as acorns and Colorado pinyon (P. edulis) seeds [76,248].
Northern and central Rocky Mountains—In the Whitefish Range in northwestern Montana, American black bears occupied 2 major habitats. Permanent home range habitat was located in low-elevation Engelmann spruce (Picea engelmannii)-subalpine fir/Oregon boxwood (Paxistima myrsinites) forest containing various seral stages. Most home range habitat had previously burned (age of burn not given), and all seral stages were used equally by American black bears except clearcuts <8 years old. Avoidance of recent clearcuts suggested that American black bears would probably not use recent burns either. Home range habitat was used for foraging during spring, for cover, and for denning. Dens were located within home range habitat and occurred most often at the bases of hollow trees (species not given), followed by rock caves, excavated underground dens, and under fallen logs. The second type of habitat used by American black bears was located outside of home ranges in sparsely forested, high-elevation (6,000 feet (1,829 m)) areas that were free of snow only during summer and fall. American black bears congregated in these areas to forage on abundant soft mast during summer and hard mast during fall .
On the Middle Fork of the Weiser River in west-central Idaho, habitat use by American black bears differed significantly (P<0.01) between seasons. Habitat was dominated by big sagebrush (Artemisia tridentata), grasses, and forbs at low elevations and ponderosa pine, Douglas-fir, and grand fir at high elevations. During spring, selection cut-open forest was preferred for foraging on grasses and forbs. During summer and fall, American black bears preferred open forest-shrubfield, shrubfield, riparian, and selection cut-forest (10 to 35 years old) because these habitats supported the densest stands of berries. Uncut forest was preferred for nightly bedding (56.9%, n=281). Clearcuts (<8 years old) were seldom used (2 of 640 American black bear locations), and rock-talus and big sagebrush-grass habitats were avoided :
|Availability and use (%) of cover types by season and activity categories for 10 female American black bears over 2 years on the Middle Fork of the Weiser River, Idaho |
|Cover type||Random availability (n=489)||Spring use (n=151)||Summer and fall use (n=483)||Foraging (n=123)||Bedding (n=281)|
|Selection cut-open forest||20.2||15.4||16.6||21.3||10.3-|
Great Lakes—In Minnesota, Wisconsin, and Michigan, American black bears prefer foraging in the following general habitats: riparian areas and alder and ash swamps with adjacent refuge trees during spring; forest openings and stands of black cherry (Prunus serotina) during summer; and mature oak stands during fall. For refuge, large eastern white pine (Pinus strobus) or eastern hemlock (Tsuga canadensis) occurring at 1 tree/6 acres are commonly used. During April and May, mothers and cubs spend >95% of their time within 300 feet (90 m) of eastern white pines or eastern hemlocks that are >8 inches (20 cm) DBH [209,212]. Quaking aspen forests of various ages are also used by American black bears in the Great Lakes region .
Northeast—For foraging and cover, 5 adult female American black bears (n=641 radio-telemetry locations) in Garrett County, Maryland, preferred wetlands and second-growth (70-90 years old) mixed forest with high stream densities over second-growth hardwood forest. Mixed forest contained conifers, which provided more escape, concealment, and thermal cover than hardwood forest. Habitats containing commercial, industrial, and residential activities were not included in any of the American black bear home ranges; however, residential and agricultural areas provided food during fall when natural food sources were scarce. Primary highways limited American black bear movements, but margins of logging roads and other roads with light traffic (<100 vehicles/day) were readily used for traveling and foraging. Wetland habitat is decreasing in Maryland, and American black bears have shown increased use of riparian habitat to compensate or substitute for wetlands .
South-central US—Within a montane desert sky island in Big Bend National Park, Texas, female American black bears preferred Mexican pinyon (P. cembroides)-oak-juniper/talus/meadow habitat for home ranges. Males preferred lower-elevation areas within smooth-leaf sotol-yucca-lechuguilla (Dasylirion leiophyllum-Yucca spp.-Agave lechuguilla)/grass; creosotebush (Larrea tridentata)-lechuguilla-mesquite (Prosopis spp.)/prickly-pear (Opuntia spp.)-grass; or oak-ponderosa pine-cypress (Cupressus spp.) habitats [175,188]. Den sites were located most often in rock outcrops and canyon walls (slopes >70%). South-facing slopes at high elevations (>5,906 feet (1,800 m)) in the southern Chisos Mountains are considered optimal denning habitat within Big Bend National Park .
In bottomland hardwood habitat in the lower Mississippi Valley, oak trees are preferred for denning . On the White River National Wildlife Refuge in Arkansas, most dens (90.2%, n=51) were located in elevated tree cavities, with openings located in the top or middle of the main trunk. Overcup oak (Q. lyrata) with a mean DBH of 39.5 inches (100.3 cm) was used most often (77.8%, n=36). Other tree species used for denning included baldcypress (Taxodium distichum) and sycamore (Platanus occidentalis). Five of 51 dens (9.8%) were located under fallen leaves on the ground. Timing and intensity of flooding influenced denning chronology and use of multiple dens. Most American black bears (55.6%, n=27) used 1 den/season, but some females used up to 4 different dens/season. Emergence from dens was delayed during a longer flooding season .
Southern Appalachians—Den sites in central hardwood forests are typically located in live trees, >35 inches (90 cm) DBH and >150 years old. Potential denning trees include eastern white pine, eastern hemlock, northern red oak (Q. rubra), chestnut oak (Q. prinus), yellow-poplar (Liriodendron tulipifera), yellow birch (Betula alleghaniensis), red maple (Acer rubrum), and white oak (Q. alba) [129,268].
In Shenandoah National Park, Virginia, 84% of pregnant American black bears denned in live tree cavities. The most common tree species used was northern red oak. Mean DBH of den trees was 38.1 inches (96.8 cm) (n=38). Mean height was 76.8 feet (23.4 m) (n=39), and mean height of cavity entrances was 32.5 feet (9.9 m) (n=39). Other trees used for denning included (in decreasing importance): white oak, yellow-poplar, snags (species not given), and white ash (Fraxinus americana) .
In Great Smoky Mountains National Park, Tennessee and North Carolina, large (38.2 inches (97.1 cm) DBH)) eastern hemlock, red maple, and northern red oak trees were preferred by American black bears for denning. Of 12 dens found, 7 were located at a mean height of 43.6 feet (13.3 m) (range 20.0-57.1 feet (6.1-17.4 m)) above ground. Two dens were located inside the bases of trees with their entrances high above the ground, 2 were beneath root networks of large trees or beneath stumps, and 1 was in the sheltered base of a red maple .
In the Pisgah Bear Sanctuary, recently logged areas (<10 years old) had mixed effects on American black bear habitat. Major forest types were eastern hemlock, cove hardwoods (yellow-poplar, magnolias (Magnolia spp.), and birches (Betula spp.)), oak-hickory, pine, and pine-hardwood mix. Early seral stages provided abundant food for American black bears, but denning habitat was poor. Increased productivity of soft mast-producing plants would last only as long as the canopy remained open .
Southeast—American black bears on the Neuse-Pamlico Peninsula in eastern North Carolina preferred marshes, clearcuts (age not given), and pocosins over large loblolly pine (Pinus taeda) plantations due to availability of superior food and cover .
On the Southeastern Coastal Plain of the United States, American black bears prefer ground nests for denning [89,101,164]. Dens located in hollow trees are sometimes used; however, few large trees are available due to intense land use practices [101,273].
Habitat use by Florida black bears probably does not change seasonally because many habitats produce food throughout the year . Riparian areas and swamps are 2 of the most important habitats for Florida black bears on the southeastern coastal plain [250,251]. At Eglin Air Force Base in northern Florida, riparian areas were preferred seasonally and annually over swamps, longleaf pine-Beyrech threeawn (P. palustris-Aristida beyrichiana) sandhills, pine (Pinus spp.), and open habitats. The closed canopy and dense understory of riparian areas provided food, denning habitat, and escape cover. Swamps ranked second in overall use and were used most often for denning. Open areas ranked lowest in preference due to lack of forested cover. During summer, pine habitat was used most often due to availability of soft mast species provided by 3- to 5-year-interval prescribed burns. During fall, sandhills habitat was used most often due to abundance of acorns .
In southern Florida, understory conditions are more important to the Florida black bear than species composition or understory height. Uplands dominated by saw-palmetto (Serenoa repens) are preferred by Florida black bears for food and cover [161,162]. A mature overstory of south Florida slash pine (P. elliottii var. densa) is not required for a saw-palmetto patch to have value to Florida black bears .
Availability of suitable den sites is not a limiting factor for Louisiana black bears. Louisiana black bears used ground nests most often in small bottomland hardwood stands, baldcypress-water tupelo (Nyssa aquatica) swamps, and coastal marshes in the Atchafalaya River Basin, Louisiana. Louisiana black bears inhabiting logged bottomland hardwood forest within a floodway used trees with elevated entrances most often. Den trees are not required for successful reproduction, but Hightower and others  recommend protecting den trees >36 inches (91 cm) DBH in areas prone to flooding. Tree species used for dens include oaks, American elm (Ulmus americana), sweetgum (Liquidambar styraciflua), and water hickory (Carya aquatica) .COVER REQUIREMENTS:
Home range and density: Home range size, distribution within home ranges, and density of American black bears are determined by sex, habitat quality, population density, distribution of food, breeding season, and topography [9,64,76,113,130,149,187,201,208,211]. Adult males have the largest home ranges, followed by adult females, yearling males, and yearling females [9,104,130,132,149,250].
Home ranges may or may not overlap between sexes and age classes depending on intraspecific relationships and habitat quality [9,104,114,130,149,187,208]. Females that are related usually have overlapping home ranges [9,106,114,148,187,187,213,223]; however, Schenk and others  found that home range overlap in Chapleau Crown Game Preserve, Ontario, was not a consequence of natal philopatric tendencies. Usually, subadult males and subadult females are allowed to stay on their mothers' home ranges for their first year of independence before dispersing (see Dispersal) . After female yearlings separate from their mothers (16-17 months of age), they live alone within their natal home range. As they get older, some expand their ranges, some leave to establish territories in adjacent areas, and some disperse several kilometers away. Mothers may shift their territories away from their daughters, probably to avoid crowding . Home ranges of adult males and females may overlap. In the Pisgah Bear Sanctuary, home ranges of males and females overlapped at home range peripheries and in core areas. Overlap increased during summer and decreased during autumn .
Home ranges may be smaller and have more overlap in mild climates and productive habitats [9,104,106,114,132,148,187,188,201,223]. In boreal forests, home ranges do not usually overlap, and territoriality between adult females is common [106,114,208,213]. This may be a consequence of low habitat productivity . In ponderosa pine-mixed conifer forests in north-central Arizona, home range size was 5 times larger in fragmented forest areas than nonfragmented areas .
Home range size is largest during the breeding season and smallest before entry into dens in fall and emergence from dens in spring. Home range size of adult females and cubs peaks when foods are most abundant, from September to October . During the breeding season in Superior National Forest, Minnesota, home ranges of males overlapped each other. Each breeding range included the territories of 7 to 15 female territories, and no males had exclusive access to any one female. After the breeding season, males migrated up to 124 miles (200 km) to forage. Foraging occurred between females' territories or on the outer 0.2 mile (0.4 km) of them. All subadult males (n=20) dispersed a mean of 38 miles (61 km; range= 8-136 miles (13-219 km)). Most males established their home ranges by 4 years old and used the home range for mating for at least 1 year after .
Topography may determine home range size, access to food resources, and/or potential mates. In Pisgah Bear Sanctuary, topography constrained size and shape of home ranges. The perimeter of home ranges aligned with ridges and valleys and home ranges were oriented on topographic features such as basins and watersheds. Steep slopes were utilized because they contained high densities of berries. American black bears avoided crossing over ridgetops to slopes on the other side probably due to high energetic costs and to avoid humans hiking along ridgelines .
Habitat use within home ranges is dictated by seasonal food production and breeding season, but a "core" use area may remain essentially unchanged throughout the year [114,149,187]. In Superior National Forest, foraging becomes the dominant activity after the breeding season ends, coinciding with the ripening of soft and hard mast. Between 40% and 69% of males and females, including females with cubs, foraged >4 miles (7 km) outside of their home ranges during late summer to access areas containing abundant food .
The table below shows mean annual home range sizes for American black bears in various geographic regions of the United States:
|Mean annual home range sizes for American black bears (km²)|
|Okanogan National Forest, Washington||289.7 (n=26)||37.1 (n=11) |
|Long Island, Washington||5.1 (n=10)||2.4 (n=13) |
|Weiser River, Idaho||112.1 (n=2)||48.9 (n=7) |
|Whitefish Range, Montana||30.1 (n=16)||5.2 (n=31) |
|Upper Peninsula of Michigan||75.6 (n=3)||48.1 (n=12) |
|Big Bend National Park, Texas||97.7 (n=7)||32.1 (n=7) |
|White River National Wildlife Refuge, Arkansas||not available||4.9 (n=16) |
|Eglin Air Force Base, Florida||351.0 (n=6)||88 (n=3) |
Habitat quality and size limit American black bear density. Density of American black bears may be greater in areas with abundant food resources [25,113,114,132,148,208]. On the Neuse-Pamlico Peninsula, densities and home ranges of adult female American black bears were higher in areas dominated by pocosins, marshes, and clearcuts compared to areas dominated by large loblolly pine plantations due to superior cover and food resources. Annual home range size for females was 6.6 km² (95% harmonic mean, n=8), and density was 1.35 American black bear/ km² in pocosins, marshes, and clearcuts. Annual home range size was 11.6 km² (n=5), and density was 0.53 American black bear/km² in loblolly pine plantations .
The estimated density of American black bears in west-central Idaho and the Shasta-Trinity National Forest, California, was 1 American black bear/0.5 mile² (1.3 km²) [25,198]. Density in the Whitefish Range of Montana ranged from 1 American black bear/0.8 mi² to 1 American black bear/1.7 mi² . On the Superior National Forest, density was 1 American black bear/4.5 km² . Density of American black bears in Coahuila, Mexico, was 0.35 American black bear/km² . In the Ozark and Ouachita Mountains in Arkansas, density was 7.5 American black bears/100 km² .FOOD HABITS:
Grasses and herbaceous plants: Due to a poor ability to digest cellulose in mature plants, American black bears consume young, green vegetation, primarily during spring . In Yukon, Canada  and the Yukon-Tanana uplands of interior Alaska, horsetail (Equisetum spp.) is important during spring and summer, comprising up to 86% of American black bear diets . Apical meristems of saw-palmetto are an important part of Florida black bear diets , and cabbage palmetto (Sabal palmetto) dominates the spring diet .
Insects: Insects obtained from coarse woody debris are important food items, primarily during summer [18,37,100,160,168,199,268]. In northeastern Oregon, Bull and others  reported higher frequencies of insect consumption than elsewhere in the United States. High consumption of insects may have been related to a shortage of other foods. Total frequency of insect occurrence in 621 American black bear scats collected between April and October over 2 years was 70%. During July of one year, total frequency of occurrence was 98%. Insects eaten included carpenter ants (Camponotus spp.), forest ants (Formica spp.), other ants (Lasius spp., Tapinoma spp., and Aphaenogaster spp.), and yellowjackets (Vespula spp. and Dolichovespula spp.) . In the Greater Yellowstone ecosystem, army cutworm moths (Euxoa auxiliaris) are eaten during summer months. Feeding sites are located on scree slopes at high elevations (x=11,010 feet (3,356 m)), with alpine tundra-covered benches and plateaus above and below feeding sites .
Soft mast: The most common soft mast eaten by American black bears are berries produced by shrubs. Some of the more important masting species include blueberries (Vaccinium spp.) [21,32], huckleberries (Vaccinium spp.), blackberries (Rubus spp.), serviceberries (Amelanchier spp.), strawberries (Fragaria spp.), autumn-olive (Elaeagnus umbellata) , and russet buffaloberry (Shepherdia canadensis) [86,87]. Saw-palmetto fruits are an important year-round food item for Florida black bears [160,162,250]. For a list of native fleshy fruits eaten by American black bears across their range, see Wilson .
Hard mast: Hard mast is important for American black bears in all geographic regions except the Pacific Northwest  and is generally more abundant in eastern portions of the American black bear's range . American black bears may travel long distances during fall looking for hard mast  and may climb up to 98 feet (30 m) in trees to forage . Hard mast eaten by American black bears may include acorns [71,91,98,114,192,198,258,264,268], hickory (Carya spp.) nuts , beechnuts (Fagus spp.) , whitebark pine (Pinus albicaulis) seeds [123,124,125,140,169,170,196], limber pine (P. flexilis) seeds , and pinyon (Pinus spp.) seeds . Acorns preferred by American black bears include those of Gambel oak in ponderosa pine habitat in the Rocky Mountains , red oak and white oak in central hardwood forests [98,247,264], and Oregon white oak in the northwestern United States and southwestern Canada [71,144]. Production of acorns is often episodic and synchronous, so acorns may not be a reliable food source .
Whitebark pine seeds are a high-quality food for American black bears due to their high digestibility, relatively large size, and high fat content. Consumption of whitebark pine seeds occurs primarily south of the western US-Canada border [123,124,125]. Use is greater in continental climates (18.7%) in the northern and central Rockies than in maritime climates (2.7%) in the northwestern United States [123,125,169]. Within the Greater Yellowstone Area, American black bear consumption of whitebark pine seeds is greatest in mature stands (>100 years old) [123,125,169]. Whitebark pine seeds are eaten primarily during fall. American black bears may also raid red squirrel (Tamiasciurus hudsonicus) whitebark pine seed caches during spring [123,124,125,140,169,196]. Whitebark pine cone production may vary widely based on site, individual trees, years, and white pine blister-rust infection. In Yellowstone National Park, large cone crops usually occur every 4 to 9 years. Seed consumption may vary considerably among years, depending on crop size. Heavy consumption of whitebark pine seeds occurs when crops average >13 to 23 cones/tree . American black bears may eat seeds up to 1 year after crop production .
In the Rocky Mountains, limber pine seeds may be an important food for American black bears when other foods are limited , and pinyon seeds are eaten in the Great Basin and southwestern United States .
Vertebrates: American black bears are more likely to eat carrion than to capture live prey ; however, they are capable of killing vertebrates. Vertebrate carrion or prey items include woodland caribou (Rangifer tarandus caribou) [41,42,238,277,280], elk (Cervis canadensis) [37,229,278], white-tailed deer (Odocoileus virginianus) , mule deer (O. hemionus) [37,207,278], and moose (Alces alces) [41,135,197,226]. Other vertebrates eaten by American black bears include Mount Graham red squirrels (Tamiasciurus hudsonicus grahamensis) , sooty grouse (Dendragapus fuliginosus) , bird eggs [23,57,205,220,265], and salmon (Oncorhynus spp.) [198,275]. Florida black bears may eat nine-banded armadillos (Dasypus novemcinctus) and feral pigs (Sus scrofa) .
Other: Stems and leaves of quaking aspen [26,132], poplar (Populus spp.) catkins, and black cottonwood buds are eaten during spring . When wild foods are scarce, American black bears may occasionally prey on domestic sheep, goats, pigs, and young cattle. They may also eat garbage, agricultural crops, and orchard fruits [67,115,167,167,213,285].
For information on forage preferences and palatability ratings of American black bears in various phases within the grand fir/Rocky Mountain maple (Acer glabrum) habitat type and the Douglas-fir/white spirea (Spiraea betulifolia) habitat types in Idaho, see Steele and Geier-Hayes [244,245]. For a list of foods eaten by American black bears by season in lodgepole pine (P. contorta) and mixed deciduous-coniferous forest in Kananaskis Country, Alberta, see Holcroft and Herrero .PREDATORS:
Silviculture: American black bears are habitat generalists that require a mosaic of habitat types and may have diverse responses to forest management . Effects of forest management on the American black bear vary depending on habitat type, landscape, and past management activities . Logging and prescribed burning may maintain a diversity of vegetation, increase cover, and increase the productivity of some important plants eaten by American black bears [7,110,113,114,173,177,208,261,263,268]. The benefits of logging and prescribed burning on shrub growth decrease once the canopy closes . Logging and prescribed burning may decrease the availability of den sites, cover, travel corridors, and trees that produce hard mast [56,193]. Disturbance of American black bears during timber harvesting may also create negative effects. Female adults with cubs often remain in their dens during timber harvest but may eventually abandon the site. Newborn cubs may die if forced to abandon dens in early spring . Despite food abundance in some logged areas, American black bears may avoid the centers of logged areas due to lack of cover and potential heat stress .
Rogers and Allen  suggest that timber management provides a diversity of vegetational age classes in close proximity to each other. Ideally, 5% to 25% of an area should be managed as an unforested cover type . Season of harvest should be considered to avoid disturbance of denning sites and foraging areas. Logging should not occur in riparian areas, seeps, or wetlands because they provide important seasonal food resources. According to Weaver , management treatments in a central hardwood landscape should maintain a diversity of hard mast species, high mast yields, and perpetuate desired hard mast-producing species in future hardwood stands.
On the Bridger-Teton National Forest in Wyoming, Irwin and Hammond  recommend providing a mosaic of successional stages by clearcutting in patches <25 acres (10 ha) on north- and east-facing slopes; planting fruit-producing shrubs in clearcuts; protecting old-growth stands of whitebark pine to provide American black bear food when berry production is low; maintaining low-elevation Douglas-fir forest on south-facing slopes; and cutting or burning quaking aspen to stimulate growth .
In southeastern Alaska, food resources for American black bears are abundant for 15 to 20 years following logging . In a 1974 report, Meehan  suggests that small patch cuts or clearcut strips with blocks or strips of timber left between are ideal for maximum wildlife production. Logged areas that are <20 years old should be available at all times, as well as mature timber and edges .
If maximizing the preharvest mammalian community is a management goal in North American boreal forests, the rate of successional convergence to predisturbance, old-growth forest may be increased by doing the following: 1) leave "moderate" amounts of coarse woody debris in harvested areas; 2) leave snags and dead wood in close proximity to live trees to form clumps; and 3) leave >30% of mature trees as clumped residuals in harvested areas .
In Maryland, Fecske and others  recommend maintaining mature mixed forest and wetland habitats. Plant conifers if necessary, and help to increase growth of rhododendron (Rhododendron spp.) thickets and other native shrubs for cover in maturing deciduous forest . On the Atlantic Coastal Plain, landscape-scale American black bear management is necessary to maintain large blocks of habitat relatively free from human activities. Pocosins and other wetlands types are important high-quality habitats for American black bear, and Jones and Pelton  state that these habitats should be maintained or restored. In seasonally-flooded forested wetlands, large trees (≥33 inches (84 cm) DBH) should be protected for Louisiana black bear denning sites .
Fragmentation of American black bear habitat from logging may make it difficult for American black bears to move between remaining habitat and may increase their vulnerability to predators. In ponderosa pine-mixed conifer habitat in north central Arizona, forest fragmentation influenced home range size, movement between usable habitat, and movement to important seasonal use areas. In fragmented habitat, American black bears were concentrated into smaller areas and became more vulnerable when moving between suitable habitat patches. Road systems created by logging also increased access by hunters. According to Mollohan and LeCount , American black bears must be managed carefully in fragmented habitat and further fragmentation should be avoided. Travel corridors should be provided between usable habitats .
Impacts of salvage logging depend on the number and condition of fire-killed trees that are retained in salvage cuts. Salvage logging may have negative impacts on wildlife by eliminating foraging and denning sites .
An American black bear habitat suitability model was created by Rogers and Allen  for northeast Minnesota, northern Wisconsin, and Michigan's Upper Peninsula and the upper half of the Lower Peninsula. The model has 3 major components: 1) variables that estimate the abundance and quality of seasonal foods in specific cover types; 2) variables used to estimate the cover type composition within an area; and 3) a variable that is used to estimate the influence of human disturbance on the habitat quality of American black bear .
Snags and coarse woody debris: Large-diameter hollow trees and coarse woody debris are important for hiding, denning, and foraging on insects [35,36,54,56,59,98,144,189,249] (see Denning and Food Habits). Cavity tree management includes maintaining existing cavity trees and snags, creating snags if they are absent [59,98,129,193,209], and leaving slash after logging for potential den sites [7,36,39,79,268]. Preserving large trees and snags is particularly important in areas with high human use, marginal habitat, and areas where flooding may occur . Potential den sites should be retained in various aspects and elevations .
In Alaska, Alberta, British Columbia, the Pacific Northwest, California, the northern Rocky Mountains, and the northern Great Basin, Bunnell and others [38,39] offer the following recommendations for the distribution of dead wood in a managed forest occupied by American black bears and other wildlife: maintain 2 to 3 large snags (>20 inches (50 cm) DBH in coastal habitat and >12 inches (30 cm) DBH in less productive habitat)) per hectare; maintain 10 to 20 smaller snags (size not given) per hectare; leave scattered logs 20 to 39 inches (50-100 cm DBH)) in 2 to 7 acre (1-3 ha) patches [38,39].
To manage for snags and coarse woody debris in the Pacific Northwest, the following management is recommended: 1) ensure sustained provision of dead and dying wood; 2) retain trees and snags of hardwoods and favored conifer species such as western larch, Douglas-fir, and ponderosa pine; 3) retain a range of size and age classes of dead wood; 4) meet dead wood requirements for large mammal species; and 5) limit salvage logging after fires [36,39]. For more information about recommended size, species, and number of logs to retain in the Columbia River Basin, see Bull and others . See Naylor  for guidelines on retaining cavity trees in eastern white pine and red pine forests in the Great Lakes-St Lawrence forest of central Ontario. See Davis  for recommendations on management of American black bear dens in western British Columbia.
To provide maximum use of slash piles for wildlife, Allen  suggest that slash piles be 100 × 25 feet (30 ×8 m) in size and adjacent to forested cover if possible . To provide sites for ground dens, Weaver  suggests piling felled tops of trees and promoting thick regeneration . White and others  recommend minimizing logging debris at low elevations (≤148.0 feet (45.1 m)) to reduce the probability of Louisiana black bears choosing flood-prone areas to den .
Retention of coarse woody debris is encouraged to provide insects for American black bear consumption [18,37,100,160,168,199,268] (see Food Habits). As logs decay, insect activity on the exterior and interior of the wood increases, enhancing the value for American black bears [35,37,60,100,199]. Bull and others  suggest retaining coarse woody debris in a variety of sizes and decay stages to enhance ant diversity.
Hard and soft mast management: Hard mast and soft mast are important seasonal foods for the American black bear [76,97,120,169,208,209,214,232] (see Food Habits). Management that promotes the establishment, diversification, proliferation, and perpetuation of soft mast-producing species is encouraged . In some locations, the temporary paucity of hard mast may be offset by the availability of soft mast, so ideally, both should be managed [117,118].
Oak regeneration is hampered by consumption of acorns by animals, insect damage of acorns, and competition by shade-tolerant vegetation . Recommendations to promote oak acorn production in eastern North America include 1) periodic thinning to promote rapid growth and vigorous crowns [97,232]; 2) managing for a diversity of mast-producing species, especially white oak and red oak; and 3) maintaining half of the management unit as mast-producing stands (40 to 80+ years old) .
Whitebark pine habitat needs to be secure for American black bears during fall and potentially during late spring and summer . According to Romme and Turner , whitebark pine habitat is projected to decrease in the future due to climate change and white pine blister rust. They advise caution when harvesting whitebark pine, especially at low elevations, and advise restricting human facilities in the whitebark pine zone .
In the absence of white pine blister rust, whitebark pines >100 years old provide productive seed crops. Good seeds crops may be produced for 200 to 300 years thereafter . In areas where American black bear management is a high priority, Mattson and Reinhart  recommend that timber be harvested in 300-year stand rotations, and landscape-wide harvest should be approximately 3%/decade. Thinning of subalpine fir is required to encourage growth of whitebark pine. Planting areas with rust-resistant whitebark pine seedlings may also promote whitebark pine . Because American black bears raid red squirrel caches for whitebark pine seeds, low red squirrel densities limit American black bear use of whitebark pine seeds. Several authors suggest favoring red squirrels in habitat with whitebark pine [123,124,125,140,169,196]. For whitebark pine restoration techniques, see the FEIS review of whitebark pine.
Costello and others  suggest that in areas where hard mast is a primary fall food for American black bears, annual mast production should be documented to forecast changes in reproductive output.
Conversion of mast-producing flatwood and hardwood communities to slash pine plantations and winter burning to control understory growth may have negative impacts on food resources for the Florida black bear . Because mast production of saw-palmetto is unpredictable in Florida black bear habitats, Stratman  suggests promoting production of acorns in upland hardwood stands with oak on the southeastern coastal plain. The size of oak stands should optimally range from 7 to 12 acres (3-5 ha), and the stands should be adjacent to riparian and swamp habitat .
Clearcutting: By opening the canopy, clearcutting increases production of early seral vegetation, providing forage and cover, benefiting American black bears. Negative consequences of clearcutting include loss of hard mast production, loss of potential den sites [54,95,149,177,209], and loss of understory trees, which may not reach suitable sizes for den use in future cutting rotations . As harvested stands age and logging slash decomposes, many resources made available by clearcutting decline .
Use of clearcuts by American black bears is determined by age, size, shape, and distribution of cutting units, as well as proximity of logging roads to American black bear habitat [209,263]. Recent clearcuts (<8 years old) are seldom used by American black bears in Montana, Idaho, and Washington [114,149,261] except to travel through . On Long Island, Washington, American black bears avoided 9- to 14-year-old clearcuts but used 18- to 25-year-old clearcuts . In the Whitefish Range in northwestern Montana, American black bears used 10-year-old clearcuts but did not use newer cuts . For more information on habitat use by American black bears in clearcut areas, see Preferred Habitat.
Clearcutting on a large scale radically alters American black bear habitat because it involves large tracts of land and extensive road systems. The negative impacts of clearcutting on American black bears could be minimized by harvesting small, irregular-shaped areas adjacent to cut areas >20 years old . The size of clearcuts relative to shape is important when determining value to wildlife. Clearcuts that are highly sinuous and follow natural contours and soil types have the smallest negative impacts . Rogers and Allen  recommend providing irregular boundaries, islands of standing timber, and travel corridors along drainages and ridgelines to offset potential negative impacts of clearcutting .Vander Heyden and Meslow  and Young and Beecham  suggest that within American black bear habitat, clearcutting either be minimized or clearcuts be small in size. To maximize food and cover for American black bears, place clearcuts adjacent to mature timber and open-canopy pole stands [263,281]. Rogers and Allen  suggest that clearcuts ideally be ≤20 acres (8 ha), and the farthest distance from forested escape cover from a clearcut be ≤820 feet (250 m).
Regeneration activities associated with clearcutting include burning slash, planting trees, and controlling weeds, shrubs, and animals that hinder tree reproduction . Clearcutting that involves posttreatment practices that involve bulldozer piling of slash, burning, and soil scarification may damage roots of berry-producing plants and be detrimental to American black bear habitat. Arno and others  and Hungerford  recommend either broadcast burning slash or leaving it untreated to protect future mast production [15,108]. Aerial application of herbicides to enhance conifer regeneration may reduce soft mast production for several years [149,208].
Tree damage: American black bears may cause damage to trees, especially in the Pacific Northwest [46,62,77,284]. During spring and early summer, American black bears may strip bark to eat new sapwood [65,145,176,176,184,253]. This typically 3.3 to 4.9 feet (1.0 to 1.5 m) from the ground , but upper boles of trees may also be stripped . American black bears do not forage on all tree species or age classes equally . Trees of any age are vulnerable to damage by American black bear [128,184,253] but pole-sized trees are most vulnerable [65,128]. In the Pacific Northwest, American black bears may damage Douglas-fir, ponderosa pine [29,62], grand fir, western redcedar , or second-growth redwood (Sequoia sempervirens) trees . In the northern Rocky Mountains, American black bears may damage western larch .
Tree damage typically occurs in thinned stands . In northwestern Montana, American black bears damaged trees 5 times more often in thinned stands compared to adjacent unthinned stands of western larch, lodgepole pine, and Engelmann spruce. Small western larch trees (4-13 inches (10-33 cm)) DBH suffered the greatest damage (63% of all trees damaged and 92% of the trees killed) . In northwestern California, American black bears damaged dense stands of pole-sized (4-20 inches (10-50 cm DBH)) redwood trees located in regenerating stands more than trees in other size classes. Density of damage was negatively correlated with distance from the edge in old-growth stands (P<0.001, t= -4.702). American black bears may benefit dense regenerating redwood stands by thinning trees. Therefore, culling American black bears to prevent tree mortality may be counterproductive and increase the need for future tree thinning .
Options for reducing tree damage and mortality include specific silviculture treatments during precommercial thinning, creating physical barriers, using American black bear repellents, supplemental feeding during the time of year when most tree damage occurs, capturing and relocating American black bears, or killing them [46,184,202]. On private lands in the Pacific Northwest, supplemental feeding programs have been successful in reducing American black bear damage . For detailed suggestions on tree damage management, see Nolte and others .
Livestock grazing: American black bears have been eliminated from much of their range by the livestock industry . Domestic livestock may compete directly with American black bears in some habitats [40,285]. According to Irwin and Hammond , Rogers and Allen , and Debyle , grazing should be curtailed or eliminated on low-elevation south slopes, riparian areas, quaking aspen stands, and high-elevation avalanche chutes to avoid competition for food resources between American black bears and livestock.
Roads: The impacts of roads on American black bears are determined by location, road structure, amount of traffic, and timing of road use. In the northern Cascade Range of Washington, roads consistently had a negative impact on habitat used by female American black bear . Roads may not be problematic for American black bears if they are gated to reduce vehicular traffic and maintained as linear wildlife openings [75,149,156,208,209,268]. Highways may reduce viability of American black bear populations by acting as barriers to intraterritorial movement, increasing mortality from motor vehicle collisions, and increasing human disturbance . Wildlife underpasses or overpasses may be constructed to provide travel corridors for American black bears under or across high-speed highways [67,94].
Hunting: Overharvest of American black bears creates a younger age structure. As populations become younger, fewer females reach puberty, reducing per capita recruitment. The age structure of the female population is then forced to an even younger average age. Full effects of overharvest do not occur until 5 to 10 years after harvest. One way to manage the sex composition of American black bear harvest is to schedule hunting seasons based on denning chronology (see Denning). Because pregnant females enter dens before males, the fall hunting season could begin after females have entered their dens. In spring, hunting of males could occur before females and young emerge from dens . According to Lee and Vaughan , managers should monitor sex ratio of harvest to ensure that females are not overharvested.
To reduce cub mortality and increase subsequent American black bear recruitment, Cunningham and others [50,52] suggest reducing hunting of females following severe fire and hunting males during spring.
Climate: During La Niña, drought may decrease food supply for American black bears and increase encounters with humans .
Other: Migration corridors are critical for linking habitat between American black bear populations [25,143,146].
According to Willson and others , areas used by American black bears for salmon foraging should be protected from human disturbance and development.American black bears may be important long-distance dispersers of some fruit seeds. Fruit seeds are dispersed when American black bears swallow them whole and defecate them intact. Germination rates of some plants may be increased by chemical or mechanical scarification that occurs in the American black bear's gut [3,18,27,85,134,210,230,257]. American black bears are unlikely to defecate intact acorns, hickory nuts, beechnuts , or pine seeds [109,141].
|Smokey the Bear as a cub, being treated for injuries sustained in a 1950 wildfire on the Lincoln National Forest, New Mexico. U.S. Forest Service photo.|
Fire may negatively impact American black bears in the short term by reducing food resources, cover, and potential den sites [31,53,69,88,136,152,194,216,250]. As production of early-seral vegetation increases, more food and cover become available [10,10,14,51,51,61,68,86,87,88,99,99,136,154,230,259]. Increased food resources in early- and midseral habitat may increase reproductive success [50,52,122,225,226] see Impacts on reproductive success). As the canopy closes in later stages of succession, availability of some foods may decrease; however, cover and potential den sites increase [121,126] (see Timing of food production and Impacts on den sites and cover).
Impacts on food production: Many plant species that American black bears consume benefit from fire [10,16,64,68,85,86,87,91,99,136]. They include grasses, forbs, fruit-producing shrubs, and some tree species [10,51,61,68,86,87,99,136]. Fire may also provide a medium for invasion of insects that American black bears eat (see Food Habits) . Immediately following a severe wildfire, American black bears may benefit from availability of carcasses of elk and deer killed by fire [30,69,80,114,235,236] and displaced small mammals along firelines .
Fire is important in the maintenance and regeneration of whitebark pine . Following low-, medium-, and high-severity fires, whitebark pine often establishes from seeds cached by the Clark's nutcracker (Nucifraga columbiana) [254,269]. Infrequent stand-replacement fires are an important component of whitebark pine's fire ecology [13,119]; however, large, stand-replacement prescribed burns are not recommended in areas where whitebark pine is in severe decline (for example, northern Idaho and northwestern Montana). Small-scale prescribed burning is recommended, especially where whitebark pine is seral; otherwise, regeneration may be extremely slow [179,180,181,240,256]. For more information about fire and whitebark pine, see the FEIS review of whitebark pine.
Frequent surface fires perpetuate oak growth in some areas by removing mid- and understory strata and reducing shading [2,22,107]. To mimic a natural disturbance pattern in mature mixed oak stands, Healy  suggests enhancing oak regeneration by conducting a shelterwood cut followed by a prescribed fire. Quaking aspen often sprouts after fire, providing a food source for the American black bear [82,267].
Fire exclusion may have adverse impacts on American black bear foraging habitat in some areas . Once-productive, seral berry fields in Oregon and Washington have been invaded by conifers. Because plants growing under a closed canopy generally produce few berries, fruit production has been steadily declining . Logging treatments that include severe soil scarification or slash burns may also reduce berry yields. Even where timber harvest favors berry production, lack of cover in early postfire years may limit American black bear use . Huckleberries and blueberries are more productive on recently burned sites compared to unburned sites. However, severe, duff-consuming fires can destroy shallow rhizomes [15,33,45,85,163,217].
Timing of food production: Availability of forage may decrease in the "short term" after fire [10,14,51,51,61,68,87,88,99,99,136,154,230,259], but may begin to increase 1 year following fire. Potter and Kessell  modeled potential feeding and reproductive habitat utilization for large mammals in any homogenous forest community. The model examined wildlife use of an unburned habitat and habitats at 0, 10, and 25 postfire years. American black bears showed the lowest preference for foraging in unburned communities and the highest preference for foraging in the postfire year 10 community .
Depending on fire severity and habitat type, soft mast production may begin to increase 1 year following fire, and abundant fruit crops may be produced for up to 20 years after fire [10,51,61,68,86,87,99,136]. Blueberry (Vaccinium spp.) and blackberry (Rubus spp.) produce the most fruit "several years" after fire . In boreal forests in the Great Lakes-St Lawrence region, blueberries, red raspberries (R. idaeus), serviceberries (Amelanchier spp.), and cherries (Prunus spp.) were most abundant 2 to 20 years after fire or logging [99,136]. In Minnesota, blueberry production increased 1 year after fire, attracting American black bears . Near Farewell, Alaska, American black bears were seen eating blueberries in late August and early September on a 5-year-old burn in habitat formerly dominated by black spruce and white spruce, ericaceous (Ericaceae) and dwarf birch shrublands, and sedge (Cyperaceae) tussock plant communities. Sightings of American black bears were incidental, and systematic wildlife inventories were not conducted .
In general, fruit production of most western huckleberry species is delayed for at least 5 years following fire. On some sites, fruit production may be reduced for 20 to 30 years or longer [15,33,45,163,217]. Refer to the FEIS reviews of evergreen huckleberry, big huckleberry, and other huckleberry species for more information about fire effects.
Russet buffaloberry is resistant to fire, surviving by root crowns and dormant buds located on the taproot . Stand-replacing prescribed burns on southern aspects led to the greatest production of russet buffaloberries at least 5 years after fire in a seral lodgepole pine and hybrid white spruce × Engelmann spruce forest in the Front Ranges of Banff National Park and the Ghost River Wilderness Area in Alberta. Fruit production began to decrease in 25-year-old burns where trees had restocked successfully. Fruit production on sites >50 years old varied depending on the site and fire characteristics. In areas that remained forest-free due to environmental factors, russet buffaloberry fruit production remained high. Two or more prescribed burns may be required to achieve the desired reduction in tree crown cover in habitat containing russet buffaloberry [86,87]. For more information about fire and russet buffaloberry, see the FEIS review of russet buffaloberry.
Three years after a wildfire in Seney National Wildlife Refuge in Michigan's Upper Peninsula, American black bears were commonly seen foraging in burned areas. Habitat use was greatest during postfire year 4, when soft mast production peaked. The 260 km² wildfire occurred in quaking aspen-paper birch habitat. Wooded wetlands, marshy grasslands, and open lakes were also common. The fire burned in a patchy pattern with varying intensities and severities, from light surface fires to severe crown fires where upper organic layers were ashed and all vegetation was consumed. Observations of American black bears in the area were incidental, and quantitative data on postfire habitat use were not collected .
In the northern Kenai Peninsula lowlands of Alaska, foods eaten by American black bears were similar between a recent burn (13-18 years old) and an old burn (35-40 years old). Major exceptions were that American black bears ate 4 times more moose calves in the recent burn, and more mountain cranberries (V. vitis-idaea) in the old burn. The 2 wildfires were located in northern coniferous forest dominated by white spruce, black spruce, balsam poplar, quaking aspen, and paper birch. The recent burn lasted 3 weeks and burned 86,490 acres (35,000 ha). Within the study area, 67% of the habitat was burned. The fire creating the old burn lasted 6 weeks and burned 308,900 acres (125,000 ha). Within the study area, 42% of the habitat was burned. Due to fuel loading, topography, and changes in fire severity, numerous "islands" of mature forest were left unburned, creating a mosaic effect with large amounts of edge. Abundant postfire vegetative growth occurred in the recent burn, increasing the moose population and providing abundant prey for American black bears during spring. Approximately 6.2 moose calves/American black bear were killed and eaten during spring in the recent burn compared to 1.2 moose calves/American black bear in the old burn. During spring and fall, mountain cranberries were eaten more frequently in the old burn because mountain cranberry had not yet recovered from the recent burn. More invertebrates were available in the old burn because the burned wood had rotted. Devil's club (Oplopanax horridus) and claspedleaf twistedstalk (Streptopus amplexifolius) were the most common foods eaten in unburned patches of the recent burn. Horsetails and bluejoint reedgrass (Calamagrostis canadensis) were available in the old and recent burns and were the only 2 plant groups consumed as green vegetation. During summer, most American black bears from both burns left their traditional use areas to forage on devil's club .
Following a severe fire within chaparral and Madrean evergreen forest in the southern Mazatzal Mountains, Arizona, American black bears extensively used unburned patches of vegetation within postfire habitats, illustrating the importance of managing a mosaic of burned and unburned habitat. Presence of shrubs in proximity to large coniferous trees was considered optimal postfire foraging and bedding habitat . According to Cunningham and others , shrub live oak-pointleaf manzanita (Quercus turbinella-Arctostaphylos pungens) chaparral reestablishment begins approximately 11 years after fire. As the density of chaparral increases, American black bears use burned areas more often. To reduce fire severity and potential negative impacts on American black bear, the authors recommend periodically removing litter via prescribed fire .
Impacts on dens and cover: Quantitative data on fire's impacts on dens and American black bear cover are scarce. Depending on fire severity, den sites and cover may or may not be negatively affected by fire. Low- to medium-severity fire may increase the density of snags and downed wood used by American black bears . A severe fire that removes large amounts of snags, coarse woody debris, and vegetative cover would most likely negatively affect American black bears [36,54,54,84,114,186,199,250].
Impacts on reproductive success: Reproductive success may increase several years following fire due to increased vegetative growth within early-successional habitat [50,52,122,225,226].
On the northern Kenai Peninsula lowlands of Alaska, density of moose was greater on a recent burn (13-18 years old) than an old burn (35-40 years old), resulting in significantly (P<0.05) greater reproductive success, cub survival, and body size of American black bears on the recent burn. In the recent burn, excellent early-successional habitat was available for moose forage, resulting in a moose population twice that of the old burn. Consumption of moose calves by American black bears was 4 times greater in the recent burn compared to the old burn. Density and litter size of American black bears were similar between recent and old burns; however, females in the recent burn bred at a younger age and had shorter reproductive intervals than females in the old burn. Survival of cubs was higher in the recent burn, but survival of subadult and adult females and males was lower. Hunting was the main cause of death for all age classes except cubs [225,226]:
|Population dynamics of moose and American black bears in a recent and old burn in the northern Kenai Peninsula lowlands of Alaska [225,226]|
(13-18 years old)
(35-40 years old)
|Density (moose/km²)||3.3 to 3.7||1.3 to 0.3||---*|
|Population trend during study||peaked||down||---|
|Population peak (yrs.)||postfire years 15-16||postfire years 13-14||---|
|Twinning rate (%)||70||22||---|
American black bears
|Age of 1st reproduction (years)||4.6||5.8||P<0.05|
|Interval between successful weanings of yearlings (years)||2.0||2.4||P<0.05|
|Subadult male survival||0.38||0.70||---|
|Subadult female survival||0.66||0.93||---|
|Adult male survival||0.77||0.90||---|
|Adult female survival||0.85||0.89||---|
|Body size||greater||smaller (kg not given)||P<0.05|
|Number of moose calves consumed by 1 American black bear/season||6.2||1.2||---|
Density of American black bears, adult survival rates, and cub production were similar between burned and unburned areas in 2 desert sky-island habitats in the southern Mazatzal Mountains, Arizona. The largest impact of the fire was lack of recruitment of cubs to the yearling age class. Elevations in both study areas ranged from 2,300 to 7,500 feet (700-2,300 m), with many slopes >45%. Habitat at low elevations (<2,900 feet (900 m)) was semidesert grassland and Arizona Sonoran desert scrub. At moderate elevations (2,900-6,100 feet (900-1,800 m)), habitat type was interior shrub live oak-pointleaf manzanita chaparral. At high elevations (>6,070 feet), habitat types were pure ponderosa pine forest and Madrean evergreen forest consisting of ponderosa pine mixed with Gambel oak, Emory oak (Q. emoryi), and other chaparral species [50,52].
A severe wildfire killed >90% of vegetation within the 237 km² burned study area. Within the burned Madrean evergreen forest, 2 patches of unburned vegetation remained (16 km² and 10.2 km²), and American black bears used them more than expected based on their availability. Within burned areas, most vegetation used for American black bear cover was removed. Trunks and large tree branches were charred but intact. Daytime cover was not available until postfire year 4, and forage was not available until postfire year 2 [50,52].
From 1997 to 2000, the number of cubs produced per female was similar between burned and unburned sites (1.3 cubs/female). In the burned area, 16 cubs were produced, and 0 survived to 1 year of age. Females with cubs had to share small, unburned patches within burned areas with adult males. Death of cubs was caused either by adult males or from malnutrition. In the unburned habitat, 13 cubs were produced, and 36% survived to 1 year of age [50,52]:
|Production and survival of American black bear cubs in the Mazatzal Mountains, Arizona from 1997 to 2000 [50,52]|
|Study area||No. breeding females||% of females producing cubs||No. cubs produced||% of cubs surviving to 1 year of age|
Prescribed fire: Prescribed fire combined with other silvicultural treatments creates and maintains suitable conditions for the American black bear by increasing food availability [82,268]. Large-scale prescribed burns are not recommended because American black bears may be displaced by lack of food, cover, and den sites. Frequent, low-severity surface fires on a small scale are recommended in most habitats because they create a variety of successional stages [34,86,111,144] and do not destroy large coarse woody debris [34,84,88,144,256,262,267].
To maximize soft mast production in open slash pine (Pinus elliottii) forests in southeastern Georgia, Johnson and Landers  suggest conducting low-severity prescribed burns at 3-year intervals. To encourage hard mast production, some longer intervals (>5 years) are encouraged .
Low-severity prescribed burns conducted at 5-year intervals benefit production of Oregon white oak. In areas with Douglas-fir encroachment, Larsen and Morgan  suggest burning every 3 to 5 years, and in areas where oak sapling growth success is critical or fuel loading is not a problem, burning every 5 to 10 years . For more recommendations on Oregon white oak restoration and enhancement for wildlife, see Larsen and Morgan .
High-severity stand-replacing prescribed burns may lead to productive russet buffaloberry feeding habitat for American black bears ≥5 years after fire. Due to potential hazards of conducting stand-replacing prescribed burns, 2 or more burns may be necessary to simulate a high-severity burn. Prescribed burning on south-facing slopes results in successful regeneration of buffaloberry .
In forests located in the southeastern US and the southern Appalachians, extensive laurel (Kalmia spp.) and rhododendron (Rhododendron spp.) thickets provide dense cover for American black bears, and prescribed fire should be used carefully in these areas . Hamilton  does not recommend prescribed fire in areas used for denning or cover by American black bears. Instead, it should be applied to heath or grass balds to stimulate growth of grasses, forbs, and fruit-producing shrubs. Low-severity burning should be conducted during winter because summer burning may reduce American black bear's food supply. Prescribed fire should also be applied with caution along the periphery of Carolina bays, and fire should be excluded from Coastal Plain hardwood swamps, sand ridges dominated by oaks, and from mountainous terrain due to potential detrimental effects on mast production and hardwood regeneration .
Small-scale prescribed burns are recommended for renewing seral whitebark pine communities at high-elevations areas where whitebark pine is badly damaged by mountain pine beetles (Dendroctonus ponderosae) and white pine blister rust . In quaking aspen habitat, prescribed burning during spring is beneficial for regeneration of quaking aspen. In older stands where fuel is lacking, prescribed burns may not be possible. A good substitute for prescribed fire in quaking aspen habitat is dormant season logging, which promotes sprout regeneration .
A late winter/early spring prescribed burn in grassland habitat in Craig Mountain Wildlife Management Area in west-central Idaho improved habitat quality for mule deer, elk, and bighorn sheep (Ovis canadensis). The effects of the prescribed fire were not examined for American black bears; however, American black bears occupied the area may have benefited from improved forage of grasses during spring. Grasslands were composed of perennial bunchgrasses. The 3 grassland types burned were: bluebunch wheatgrass (Pseudoroegneria spicata)/plains prickly-pear (Opuntia polyacantha), bluebunch wheatgrass/Sandberg bluegrass (Poa secunda), and Idaho fescue (Festuca idahoensis)-bluebunch wheatgrass. Elevation ranged from 800 to 3,600 feet (200-1,100 m), and slopes ranged from 20% to 80%. Three-thousand acres (1,214 ha) were burned in late February and mid-March. The fire created a mosaic pattern, burning 30% to 65% of the area. Prior to fire exclusion, fires occurred in the area every 10 to 25 years. The fire was an effective tool for maintaining, rejuvenating, and improving big game winter ranges .
Evidence suggests that most oaks are favored by relatively frequent fires [1,11,17,151,218,262,279]. A series of low-severity prescribed fires prior to timber harvest can promote advanced regeneration of white oak. In the southern Appalachians, biennial summer fires are often most effective in promoting advance regeneration [262,266]. In upland habitat of the southeastern coastal plain of Florida, Stratman  recommends prescribed fire intervals of 7 to 10 years to promote oak regeneration and mast production. In stands dominated by oak, advance regeneration in the understory is a prerequisite for reestablishment subsequent to timber harvest [34,262]. To favor oak reproduction and establishment, Brose and Van Lear  recommend prescribed fires at intervals of 3 to 5 years following shelterwood cuts in upland stands with advance oak regeneration . Refer to the FEIS reviews of northern red oak, white oak, Oregon white oak, and other oak species used by American black bears for more information about fire effects to oaks.
In sand pine (P. clausa)-scrub habitat in Ocala National Forest, Florida, full recovery of vegetation occurred 16 months following a prescribed stand-replacement fire. Three months after the fire, Florida black bears ate apical meristems from 50% of saw-palmetto and scrub palmetto (Sabal etonia) sprouts . A mosaic of recent burns and relatively fire-free pine and saw-palmetto habitat is most beneficial for Florida black bears, and regular production of saw-palmetto fruits cannot be expected with frequent prescribed burning . Maehr and others  recommend maintaining saw-palmetto in several stages of postfire recovery. Patches of saw-palmetto should be maintained at 1- to 20-postfire-year intervals to provide food, cover, and den sites .
Florida black bears showed the highest annual use of 2-year-old and 6-year-old prescribed burns in longleaf pine-Beyrech threeawn sandhills and pine (Pinus spp.) habitat in northern Florida. Burns <1 year old did not provide American black bears with adequate food resources or escape cover. High use of 2-year-old and 6-year-old burns was probably attributed to peak production of mast species and proximity to riparian areas used for cover. During fall, 2-year-old and 5-year-old burns resulting form low-severity fire were used most often. The low-severity of fall burns probably allowed high survival of oaks. In upland habitat, low-severity prescribed fire intervals of 3 to 5 years benefits Florida black bears by stimulating mast production of plants such as huckleberry, ground blueberry (V. myrsinites), sweet gallberry (Ilex coriacea), bitter gallberry (I. glabra), and greenbrier (Smilax spp.). A fire cycle >5 years stimulates mast production of highbush blueberry (V. corymbosum), sparkleberry (V. arboreum), black tupelo (Nyssa sylvatica), and common persimmon (Diospyros virginiana). Winter fire exclusion prevents disturbance of denning Florida black bears .
Hall  and Weaver  recommend protecting snags and coarse woody debris during prescribed burning. Before conducting a prescribed burn, potential den trees and large (>20 inches (50 cm)), hollow logs should be protected from fire by removing combustible material from the immediate areas [84,268].
The following table provides fire regime information on vegetation communities in which American black bear may occur, based on the habitat characteristics and species composition of communities American black bear are known to occupy. There is not conclusive evidence that American black bear occur in all the habitat types listed, and some community types, especially those used rarely, may have been omitted. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find Fire Regimes".
|Fire regime information on vegetation communities in which American black bear may occur. For each community, fire regime characteristics are taken from the LANDFIRE Rapid Assessment Vegetation Models . These vegetation models were developed by local experts using available literature, local data, and/or expert opinion as documented in the PDF file linked from each Potential Natural Vegetation Group listed below. Cells are blank where information is not available in the Rapid Assessment Vegetation Model.|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Alpine and subalpine meadows and grasslands||Replacement||68%||350||200||500|
|Oregon white oak-ponderosa pine||Replacement||16%||125||100||300|
|Surface or low||81%||25||5||30|
|Pine savannah (ultramafic)||Replacement||7%||200||100||300|
|Surface or low||93%||15||10||20|
|Surface or low||78%||13|
|Oregon white oak||Replacement||3%||275|
|Surface or low||78%||12.5|
|Sitka spruce-western hemlock||Replacement||100%||700||300||>1,000|
|Douglas-fir (Willamette Valley foothills)||Replacement||18%||150||100||400|
|Surface or low||53%||50||20||80|
|Ponderosa pine (xeric)||Replacement||37%||130|
|Surface or low||16%||300|
|Dry ponderosa pine (mesic)||Replacement||5%||125|
|Surface or low||82%||8|
|Douglas-fir-western hemlock (dry mesic)||Replacement||25%||300||250||500|
|Douglas-fir-western hemlock (wet mesic)||Replacement||71%||400|
|Mixed conifer (southwestern Oregon)||Replacement||4%||400|
|Surface or low||67%||22|
|California mixed evergreen (northern California)||Replacement||6%||150||100||200|
|Surface or low||64%||15||5||30|
|Lodgepole pine (pumice soils)||Replacement||78%||125||65||200|
|Pacific silver fir (low elevation)||Replacement||46%||350||100||800|
|Pacific silver fir (high elevation)||Replacement||69%||500|
|Mixed conifer (eastside dry)||Replacement||14%||115||70||200|
|Surface or low||64%||25||20||25|
|Mixed conifer (eastside mesic)||Replacement||35%||200|
|Surface or low||18%||400|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Wet mountain meadow-Lodgepole pine (subalpine)||Replacement||21%||100|
|Surface or low||69%||30|
|Alpine meadows and barrens||Replacement||100%||200||200||400|
|Coastal sage scrub-coastal prairie||Replacement||8%||40||8||900|
|Surface or low||62%||5||1||6|
|California oak woodlands||Replacement||8%||120|
|Surface or low||91%||10|
|Surface or low||78%||13|
|California mixed evergreen||Replacement||10%||140||65||700|
|Surface or low||32%||45||7|
|Surface or low||98%||20|
|Mixed conifer (North Slopes)||Replacement||5%||250|
|Surface or low||88%||15||10||40|
|Mixed conifer (South Slopes)||Replacement||4%||200|
|Surface or low||80%||10|
|Aspen with conifer||Replacement||24%||155||50||300|
|Surface or low||61%||60|
|Surface or low||74%||30|
|Mixed evergreen-bigcone Douglas-fir (southern coastal)||Replacement||29%||250|
|Interior white fir (northeastern California)||Replacement||47%||145|
|Surface or low||21%||325|
|Red fir-white fir||Replacement||13%||200||125||500|
|Surface or low||51%||50||15||50|
|Red fir-western white pine||Replacement||16%||250|
|Surface or low||19%||200|
|Sierra Nevada lodgepole pine (cold wet upper montane)||Replacement||23%||150||37||764|
|Surface or low||7%||500|
|Sierra Nevada lodgepole pine (dry subalpine)||Replacement||11%||250||31||500|
|Surface or low||45%||60||9||350|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Surface or low||15%||67|
|Desert grassland with shrubs and trees||Replacement||85%||12|
|Shortgrass prairie with trees||Replacement||80%||15||2||35|
|Plains mesa grassland||Replacement||81%||20||3||30|
|Plains mesa grassland with shrubs or trees||Replacement||76%||20|
|Montane and subalpine grasslands||Replacement||55%||18||10||100|
|Surface or low||45%||22|
|Montane and subalpine grasslands with shrubs or trees||Replacement||30%||70||10||100|
|Surface or low||70%||30|
|Salt desert scrubland||Replacement||13%||200||100||300|
|Southwestern shrub steppe||Replacement||72%||14||8||15|
|Surface or low||15%||69||60||100|
|Southwestern shrub steppe with trees||Replacement||52%||17||10||25|
|Surface or low||25%||35||25||100|
|Interior Arizona chaparral||Replacement||100%||125||60||150|
|Madrean oak-conifer woodland||Replacement||16%||65||25|
|Surface or low||76%||14||1||20|
|Pinyon-juniper (mixed fire regime)||Replacement||29%||430|
|Surface or low||6%||>1,000|
|Pinyon-juniper (rare replacement fire regime)||Replacement||76%||526|
|Surface or low||4%||>1,000|
|Ponderosa pine/grassland (Southwest)||Replacement||3%||300|
|Surface or low||97%||10|
|Bristlecone-limber pine (Southwest)||Replacement||67%||500|
|Surface or low||33%||>1,000|
|Riparian forest with conifers||Replacement||100%||435||300||550|
|Riparian deciduous woodland||Replacement||50%||110||15||200|
|Surface or low||30%||180||10|
|Ponderosa pine-Gambel oak (southern Rockies and Southwest)||Replacement||8%||300|
|Surface or low||92%||25||10||30|
|Ponderosa pine-Douglas-fir (southern Rockies)||Replacement||15%||460|
|Surface or low||43%||160|
|Southwest mixed conifer (warm, dry with aspen)||Replacement||7%||300|
|Surface or low||80%||25||2||70|
|Southwest mixed conifer (cool, moist with aspen)||Replacement||29%||200||80||200|
|Surface or low||36%||160||10|
|Aspen with spruce-fir||Replacement||38%||75||40||90|
|Surface or low||23%||125||30||250|
|Stable aspen without conifers||Replacement||81%||150||50||300|
|Surface or low||19%||650||600||>1,000|
|Lodgepole pine (Central Rocky Mountains, infrequent fire)||Replacement||82%||300||250||500|
|Surface or low||18%||>1,000||>1,000||>1,000|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Great Basin Grassland|
|Mountain meadow (mesic to dry)||Replacement||66%||31||15||45|
|Great Basin Shrubland|
|Wyoming big sagebrush semidesert with trees||Replacement||84%||137||30||200|
|Surface or low||5%||>1,000||20||>1,000|
|Wyoming sagebrush steppe||Replacement||89%||92||30||120|
|Interior Arizona chaparral||Replacement||88%||46||25||100|
|Mountain big sagebrush with conifers||Replacement||100%||49||15||100|
|Mountain shrubland with trees||Replacement||22%||105||100||200|
|Black and low sagebrushes with trees||Replacement||37%||227||150||290|
|Surface or low||31%||250||50|
|Great Basin Woodland|
|Juniper and pinyon-juniper steppe woodland||Replacement||20%||333||100||>1,000|
|Surface or low||49%||135||100|
|Surface or low||78%||13|
|Great Basin Forested|
|Interior ponderosa pine||Replacement||5%||161||800|
|Surface or low||86%||9||8||10|
|Surface or low||39%||65||15|
|Great Basin Douglas-fir (dry)||Replacement||12%||90||600|
|Surface or low||75%||14||10||50|
|Aspen with conifer (low to midelevation)||Replacement||53%||61||20|
|Surface or low||23%||143||10|
|Douglas-fir (warm mesic interior)||Replacement||28%||170||80||400|
|Aspen with conifer (high elevation)||Replacement||47%||76||40|
|Surface or low||35%||100||10|
|Stable aspen-cottonwood, no conifers||Replacement||31%||96||50||300|
|Surface or low||69%||44||20||60|
|Aspen with spruce-fir||Replacement||38%||75||40||90|
|Surface or low||23%||125||30||250|
|Stable aspen without conifers||Replacement||81%||150||50||300|
|Surface or low||19%||650||600||>1,000|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Northern Rockies Grassland|
|Northern Rockies Shrubland|
|Wyoming big sagebrush||Replacement||63%||145||80||240|
|Mountain shrub, nonsagebrush||Replacement||80%||100||20||150|
|Mountain big sagebrush steppe and shrubland||Replacement||100%||70||30||200|
|Northern Rockies Woodland|
|Northern Rockies Forested|
|Ponderosa pine (Northern Great Plains)||Replacement||5%||300|
|Surface or low||75%||20||10||40|
|Ponderosa pine (Northern and Central Rockies)||Replacement||4%||300||100||>1,000|
|Surface or low||77%||15||3||30|
|Ponderosa pine (Black Hills, low elevation)||Replacement||7%||300||200||400|
|Surface or low||71%||30||5||50|
|Ponderosa pine (Black Hills, high elevation)||Replacement||12%||300|
|Surface or low||71%||50|
|Surface or low||39%||65||15|
|Douglas-fir (xeric interior)||Replacement||12%||165||100||300|
|Surface or low||69%||28||15||40|
|Douglas-fir (warm mesic interior)||Replacement||28%||170||80||400|
|Grand fir-Douglas-fir-western larch mix||Replacement||29%||150||100||200|
|Mixed conifer-upland western redcedar-western hemlock||Replacement||67%||225||150||300|
|Western larch-lodgepole pine-Douglas-fir||Replacement||33%||200||50||250|
|Grand fir-lodgepole pine-larch-Douglas-fir||Replacement||31%||220||50||250|
|Persistent lodgepole pine||Replacement||89%||450||300||600|
|Whitebark pine-lodgepole pine (upper subalpine, Northern and Central Rockies)||Replacement||38%||360|
|Lower subalpine lodgepole pine||Replacement||73%||170||50||200|
|Lower subalpine (Wyoming and Central Rockies)||Replacement||100%||175||30||300|
|Upper subalpine spruce-fir (Central Rockies)||Replacement||100%||300||100||600|
|Northern Great Plains|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Northern Plains Grassland|
|Surface or low||76%||4|
|Northern Plains Woodland|
|Surface or low||98%||7.5|
|Great Plains floodplain||Replacement||100%||500|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Great Lakes Grassland|
|Mosaic of bluestem prairie and oak-hickory||Replacement||79%||5||1||8|
|Surface or low||20%||2||33|
|Great Lakes Woodland|
|Great Lakes pine barrens||Replacement||8%||41||10||80|
|Surface or low||83%||4||1||20|
|Jack pine-open lands (frequent fire-return interval)||Replacement||83%||26||10||100|
|Northern oak savanna||Replacement||4%||110||50||500|
|Surface or low||87%||5||1||20|
|Great Lakes Forested|
|Northern hardwood maple-beech-eastern hemlock||Replacement||60%||>1,000|
|Conifer lowland (embedded in fire-prone system)||Replacement||45%||120||90||220|
|Conifer lowland (embedded in fire-resistant ecosystem)||Replacement||36%||540||220||>1,000|
|Great Lakes floodplain forest|
|Surface or low||93%||61|
|Great Lakes spruce-fir||Replacement||100%||85||50||200|
|Minnesota spruce-fir (adjacent to Lake Superior and Drift and Lake Plain)||Replacement||21%||300|
|Surface or low||79%||80|
|Great Lakes pine forest, jack pine||Replacement||67%||50|
|Surface or low||10%||333|
|Surface or low||67%||500|
|Maple-basswood mesic hardwood forest (Great Lakes)||Replacement||100%||>1,000||>1,000||>1,000|
|Surface or low||89%||35|
|Northern hardwood-eastern hemlock forest (Great Lakes)||Replacement||99%||>1,000|
|Surface or low||76%||11||2||25|
|Surface or low||81%||85|
|Red pine-white pine (frequent fire)||Replacement||38%||56|
|Surface or low||26%||84|
|Red pine-white pine (less frequent fire)||Replacement||30%||166|
|Surface or low||23%||220|
|Great Lakes pine forest, eastern white pine-eastern hemlock (frequent fire)||Replacement||52%||260|
|Surface or low||35%||385|
|Eastern white pine-eastern hemlock||Replacement||54%||370|
|Surface or low||34%||588|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Northern coastal marsh||Replacement||97%||7||2||50|
|Eastern woodland mosaic||Replacement||2%||200||100||300|
|Surface or low||89%||4||1||7|
|Rocky outcrop pine (Northeast)||Replacement||16%||128|
|Surface or low||52%||40|
|Surface or low||65%||12|
|Oak-pine (eastern dry-xeric)||Replacement||4%||185|
|Surface or low||90%||8|
|Northern hardwoods (Northeast)||Replacement||39%||>1,000|
|Eastern white pine-northern hardwoods||Replacement||72%||475|
|Surface or low||28%||>1,000|
|Northern hardwoods-eastern hemlock||Replacement||50%||>1,000|
|Surface or low||50%||>1,000|
|Appalachian oak forest (dry-mesic)||Replacement||2%||625||500||>1,000|
|Surface or low||92%||15||7||26|
|Northeast spruce-fir forest||Replacement||100%||265||150||300|
|Southeastern red spruce-Fraser fir||Replacement||100%||500||300||>1,000|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|South-central US Grassland|
|Surface or low||93%||3||1||4|
|South-central US Shrubland|
|Southwestern shrub steppe||Replacement||76%||12|
|South-central US Woodland|
|Surface or low||99%||3.2|
|Interior Highlands dry oak/bluestem woodland and glade||Replacement||16%||25||10||100|
|Surface or low||80%||5||2||7|
|Interior Highlands oak-hickory-pine||Replacement||3%||150||100||300|
|Surface or low||97%||4||2||10|
|Surface or low||96%||4|
|South-central US Forested|
|Interior Highlands dry-mesic forest and woodland||Replacement||7%||250||50||300|
|Surface or low||75%||22||5||35|
|Gulf Coastal Plain pine flatwoods||Replacement||2%||190|
|Surface or low||95%||5|
|West Gulf Coastal plain pine (uplands and flatwoods)||Replacement||4%||100||50||200|
|Surface or low||93%||4||4||10|
|West Gulf Coastal Plain pine-hardwood woodland or forest upland||Replacement||3%||100||20||200|
|Surface or low||94%||3||3||5|
|Surface or low||58%||100|
|Southern floodplain (rare fire)||Replacement||42%||>1,000|
|Surface or low||58%||714|
|Surface or low||94%||6|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Southern Appalachians Grassland|
|Eastern prairie-woodland mosaic||Replacement||50%||10|
|Surface or low||50%||10|
|Southern Appalachians Woodland|
|Appalachian shortleaf pine||Replacement||4%||125|
|Surface or low||92%||6|
|Table Mountain-pitch pine||Replacement||5%||100|
|Surface or low||92%||5|
|Surface or low||49%||55|
|Southern Appalachians Forested|
|Bottomland hardwood forest||Replacement||25%||435||200||>1,000|
|Surface or low||51%||210||50||250|
|Mixed mesophytic hardwood||Replacement||11%||665|
|Surface or low||79%||90|
|Surface or low||89%||6||3||10|
|Eastern hemlock-eastern white pine-hardwood||Replacement||17%||>1,000||500||>1,000|
|Surface or low||83%||210||100||>1,000|
|Oak (eastern dry-xeric)||Replacement||6%||128||50|
|Surface or low||78%||10||1||10|
|Appalachian Virginia pine||Replacement||20%||110||25||125|
|Surface or low||64%||35||10||40|
|Appalachian oak forest (dry-mesic)||Replacement||6%||220|
|Surface or low||79%||17|
|Southern Appalachian high-elevation forest||Replacement||59%||525|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Southeast Gulf Coastal Plain Blackland prairie and woodland||Replacement||22%||7|
|Everglades (marl prairie)||Replacement||45%||16||10||20|
|Surface or low||9%||20|
|Pond cypress savanna||Replacement||17%||120|
|Surface or low||57%||35|
|Gulf Coast wet pine savanna||Replacement||2%||165||10||500|
|Surface or low||98%||3||1||10|
|Surface or low||97%||4||1||5|
|Longleaf pine (mesic uplands)||Replacement||3%||110||40||200|
|Surface or low||97%||3||1||5|
|Longleaf pine-Sandhills prairie||Replacement||3%||130||25||500|
|Surface or low||97%||4||1||10|
|Surface or low||99%||3||1||5|
|Surface or low||10%||43||2||50|
|South Florida slash pine flatwoods||Replacement||6%||50||50||90|
|Surface or low||94%||3||1||6|
|Atlantic wet pine savanna||Replacement||4%||100|
|Surface or low||94%||4|
|Sand pine scrub||Replacement||90%||45||10||100|
|Coastal Plain pine-oak-hickory||Replacement||4%||200|
|Surface or low||89%||8|
|Atlantic white-cedar forest||Replacement||34%||200||25||350|
|Surface or low||59%||115||10||500|
|Surface or low||80%||9||3||50|
|Surface or low||97%||2||1||8|
|Loess bluff and plain forest**||Replacement||7%||476|
|Surface or low||85%||39|
|Surface or low||93%||63|
Replacement=Any fire that causes greater than 75% top removal of a vegetation-fuel type, resulting in general replacement of existing vegetation; may or may not cause a lethal effect on the plants.
Mixed=Any fire burning more than 5% of an area that does not qualify as a replacement, surface, or low-severity fire; includes mosaic and other fires that are intermediate in effects
Surface or low=Any fire that causes less than 25% upper layer replacement and/or removal in a vegetation-fuel class but burns 5% or more of the area [90,137].
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