The Arctic Bumblebee (Bombus polaris)

By Zoe Statman-Weil and Vicki Wojcik, Pollinator Partnership

Bombus polaris, known as the arctic bumblebee, has a unique challenge when compared to the other bumble bees. It lives in a strikingly cold climate and requires a greater effort to regulate its temperature. Bombus polaris is found in very northern reaches of Alaska, Canada, Northern Scandinavia, and Russia.

Bombus polaris feeding on flower blossom.
Bombus polaris feeding on flower blossom. Photo by Joaquim Alves Gaspar, from Wikimedia.

With its unique living situation, there is no surprise that the primary research conducted on Bombus polaris relates to its temperature regulation. Bumble bees, like other insects, are poikilothermic or "cold-blooded", but they have some special behavioral and physiological adaptations that allow them to overcome cool temperatures. On sunny days, you can see Bombus polaris queens and workers basking in the sunlight, warming their bodies for flight. These bees will often take advantage of the solar reflective qualities of conical flowers, like the arctic poppy, which act like mini-magnifying glasses that concentrate the sun’s rays. Sitting inside of a flower helps the bee raise its body temperature more quickly.

Bumble bees have another key mechanism that they can use to heat their body - large flight muscles. Bumble bees can shiver these large muscles and generate enough heat to bring their body temperature up to the minimum flight temperature of 86 degrees Fahrenheit. This shivering technique allows the Bombus polaris to heat its thorax up to 60 degrees Fahrenheit above the air temperature! Hairier than most other bumble bees, it has thick ‘fur’ to trap in and conserve heat.

This arctic bumblebee usually has a black thorax with orange or yellow edges and an orange or yellow abdomen that can have a black tip. Being large is an asset to species living in colder climates, and Bombus polaris, while an insect and relatively small, is large for its type. In this way, while it takes more energy to heat up a larger body, the larger body will also retain heat for a longer period of time.

All of these adaptations allow the arctic bumble bee to start its life cycle as soon as the snow starts to melt, even before flowers come into bloom. At the beginning of the spring season in mid-May arctic willow trees start to blossom and you can see Bombus polaris queens emerging from their winter hibernation to feed on this early source of nectar. It will be another two weeks and well into June before the workers appear.

Like many members of the genus Bombus, Bombus polaris is known to feed on berries and shrubs, including alpine bearberry(Arctostaphylos alpine), black crowberry(Empetrum nigrum), bog blueberry(Vaccinium uliginosum), and lingonberry(Vaccinium vitis-idaea). It is also a key pollinator of many far northern species, including arctic willow (Salix arctica), arctic rose (Rosa acicularis), red current (Ribes rubrum), and arctic poppy (Papaver radicatum).

Life in the arctic is challenging, and not without predators. Pollinating insects in all ecosystems serve as food sources for many avian, mammalian, and reptilian predators, and the arctic is no different. The Buff-breasted Sandpiper (Tryngites subruficollis), Common Eider (Somateria mollissima), and Old Squaw (Clangula hyemalis) all make a meal out of Bombus polaris or feed them to their young. Bombus polaris is even subjected to nest predation by arctic cuckoo bumble bee, Bombus hyperboreaus, which can take over its nest and have the hard working Bombus polaris sisters raise its young.

From predation to cold temperatures, the artic bumble bee certainly has some obstacles, but its survival techniques have proven successful!

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