Assessing polar bear (Ursus maritimus) in a changing Arctic using non-invasive DNA metabarcoding

• Main Author: Landon, Emily
• Other Authors: Biology, Lougheed, Stephen
• Format: Thesis
• Language: English
• Published: 2023
• Subjects: polar bear; diet; DNA metabarcoding; blocking primer; Arctic; Canada; Arctic birds; Climate change; Sea ice; toothed whales; Ursus maritimus
• Online Access: http://hdl.handle.net/1974/31431

Dietary studies of apex predators enhance our understanding of species’ life histories, predator-prey interactions and food webs. Studies of diet over time can reveal changes in these life history and ecology that result from climate change and landscape disturbances. Polar bears (Ursus maritimus) reside at the top of Arctic food webs. Because polar bears use both sea ice and land throughout their annual cycle, they integrate trophic information from both marine and terrestrial ecosystems across their vast territories, including availability and diversity of prey species. Polar bears act as sentinels of environmental change as they are highly adapted to using sea ice as a platform for foraging and are therefore vulnerable to current and projected changes in Arctic sea ice conditions. Given that these changes in sea ice conditions are projected to alter the composition and accessibility of polar bear prey species, and the pressing need for more non-invasive wildlife monitoring strategies, this study investigates what dietary information could be retrieved from 743 polar bear fecal samples from across the Canadian Arctic using novel multi-marker DNA metabarcoding to identify Arctic birds, fish, and mammals at family- and species-level resolution. I designed two novel blocking primers specific to polar bear DNA to maximize detection of prey taxa within fecal samples. Over 8 million metabarcoding sequences were retrieved, identifying 31 prey species, belonging to 19 families, representing 14 orders. As expected, polar bears consume Arctic seal species (Phocidae), present in >70% of successfully sequenced fecal samples – more common than any other prey group. The dietary signature of taxa such as seals, small toothed whales, various seabirds, and caribou confirm previous observations of components of polar bear diet, however, the frequency of detection of several terrestrial taxa and seabird species are consumed may represent novel insights reflecting predator-scavenger relationships and shifts in the diet of the ...