Arctic brown bears like salmon, too!

A female Brown Bear with two cubs fishing in a tributary of the Noatak River, Alaska on July 28, 2017.

NPS/Matthew Cameron

Interior brown bears living above the Arctic Circle are different than the brown bears that live along the coast. Brown bears on the coast of Alaska gorge themselves on the plentiful salmon runs and grow to massive proportions. Because of the plentiful food supplies, bears on the coast congregate in larger groups, showing a greater tolerance for each other than interior bears. Interior bears tend to be more solitary and have to work harder to find food (green vegetation, berries, and occasional prey or carrion) and are generally smaller in size because of it. So we were surprised when local bush pilots reported seeing brown bears congregate along Arctic rivers during August and September. This suggested that there was more to the story.

We used data from GPS-collared brown bears in and around Gates of the Arctic National Park and Preserve to identify streams where brown bears might be fishing for salmon from 2014 to 2016. We visited multiple streams across three major watersheds--the Kobuk River, the Koyukuk River, and the Noatak River--to document how much bears used salmon. In some cases, this was the first documentation of these streams supporting salmon. As the pilots suggested, we observed bears fishing or found evidence of where bears had fished (such as piles of salmon gill plates) at all three rivers. We even observed 11 bears congregating along a half mile of river on a tributary of the Noatak River--an impressive density of brown bears so far north in the Arctic.

While these Arctic bears don’t have the glut of salmon that coastal bears do, it was interesting to know that they found salmon hundreds of miles from the sea and were willing to share space with other bears to take advantage of the energy-rich food. These findings, published recently in the Canadian Field Naturalist, broadens our understanding of the resources that bears rely on to survive in the harsh northern environment.

Use of salmon (Oncorhynchus spp.) by Brown Bears (Ursus arctos) in an Arctic, interior, montane environment

Abstract

Salmon (Oncorhynchus spp.) is a key dietary item for temperate coastal Brown Bears (Ursus arctos) across much of their circumpolar range. Brown Bears living in Arctic, interior, and montane environments without large annual runs of salmon tend to be smaller bodied and occur at much lower densities than coastal populations. We conducted ground and aerial surveys to assess whether Brown Bears fished for salmon above the Arctic Circle, in and around Gates of the Arctic National Park and Preserve. Here, we document the use of salmon by interior Brown Bears in the Arctic mountains of the central Brooks Range of Alaska. We believe our findings could be important for understanding the breadth of the species’ diet across major biomes, as well as visitor safety in the park and Brown Bear conservation in the region.

Sorum, M. S., K. Joly, and M. D. Cameron. 2019. Use of salmon (Oncorhynchus spp.) by brown bears (Ursos arctos) in an Arctic, interior, montane environment. The Canadian Field-Naturalist 133(2):151-155.