After several years of studying brown bear ecology on Alaska’s Kodiak Island, I grew used to walking up streams into scenes of carnage. Where bears had killed and eaten spawning sockeye salmon, streambeds were littered with fish heads, jaws and whole carcasses, and plants on the stream banks were flattened. But at the peak of the stream spawning run in 2014, I was puzzled to find no bears or salmon parts. Salmon were dying naturally after spawning and piling up in streams, intact.
I’ve spent the last three years trying to solve this ecological puzzle. After extensive field and lab work along with researchers from Kodiak National Wildlife Refuge, Flathead Lake Biological Station and Oregon State University, we arrived at a fascinating conclusion.
In warm years, another favorite bear food — red elderberries — ripened early enough to overlap with the salmon season. This forced bears to choose between the foods. Surprisingly, almost all bears opted for berries over salmon. This choice has likely altered food webs, and will become increasingly common with expected climate warming.
Our team was struck by the bears’ seemingly counterintuitive switch. Why would bears stop eating a high-protein food loaded with energy? Quickly, though, …read more