Reproductive Ecology of the Foothill Yellow-legged Frog (Rana boylii) in Hurdygurdy Creek, Northwestern California: Implications for Species Conservation and Management
The primary objective of this study is to observe and describe the nature of the undocumented mating system/strategy of one or several breeding populations of the foothill yellow-legged frog using digital video and analog audio recordings. In addition, we will utilize a mark-recapture technique to examine movement patterns relative to breeding activity and breeding site fidelity.
A survey of a 4.5 km creek reach at Hurdygurdy Creek (Smith River tributary) is conducted prior to breeding activity, during breeding activity, and several times following breeding activity. Frogs are marked using passive integrated transponders (PIT tags), programmed with unique number codes.
During observation periods we identify individuals by reading their PIT tags. We mark individuals with different colored beaded belts in order to visually identify them during observations. Individuals positions within the breeding area are thoroughly documented throughout the day. Marking individuals allows us to record interactions (agonistic behavior and amplexus) between specific individuals, accurately keep track of the location of individuals within the breeding site, and determine calling site displacements of one individual by another.
In addition to the main objectives of the study, we are testing the feasibility of using natural mottling patterns as a method of individual frog identification. We photograph the chin of each individual captured. We will then compare photos from original captures to any subsequent recaptures to identify if there are seasonal pattern variations and if patterns change with frog maturation.
During the spring of 2002 we observed a previously unreported oviposition behavior of Rana boylii in which a female frog prepared a cobble for egg mass attachment. The female frog, with the male frog gripping her dorsal side (amplexus), was positioned so that her hind feet were resting against a cobble. The female began scraping the surface of the cobble, loosening particles of algae and sediment that were on the surface of the rock. After scraping ceased, the female released her eggs on the "cleaned" area of the cobble. (Wheeler et. al., Herpetological Review, in review).
To view video footage of scraping behavior (left image) and oviposition (right image), open this page in MS Internet Explorer 3 or higher, then click on the appropriate image. The footage will temporarily only be available for viewing on Windows 98 or newer operating systems. The scraping video is 108KB and the ovipositing video is 263KB.
Last updated on November 22, 2002, by Garth Hodgson