Stable isotope differences of polar bears in the Southern Beaufort Sea and Chukchi Sea

The life history, genetic, and habitat use differences between the 2 polar bear (Ursus maritimus) subpopulations in Alaska have been used to determine the geographic border separating them, but it has sparked a debate of the correct placement of the border for several years. Recently, the Southern Beaufort Sea (SBS) polar bear subpopulation has declined due to sea ice loss, while the Chukchi Sea (CS) subpopulation appears stable. To provide additional information about potential differences between the SBS and CS subpopulations, such as differences in prey sources, we used stable isotope analysis of carbon and nitrogen from bone collagen of polar bears in these 2 neighboring subpopulations.  We analyzed polar bear bones (1954–2019) from 112 individuals. Our purpose was to determine if the SBS and CS subpopulations could be distinguished based on the stable isotope signatures of bone collagen. A difference greater than 1‰ in δ13C values suggests a change in carbon sources, such as nearsh...