As the climate has changed, polar bears have shifted their diets in response, several new papers published in 2013 showed.
Melting sea ice
Declines in sea ice have meant that polar bears in the western Hudson Bay cannot hunt their main prey for longer stretches of the year.
Historically, polar bears have mainly hunted for seals in gaps in the sea ice.
When the sea ice melts in summer, polar bears come ashore. Then they also eat land-based foods such as snow geese.
To see how climate change had affected polar bear diet, Linda Gormezano, a researcher at the American Museum of Natural History, and her colleagues, used a Dutch Shepard dog named Quinoa to find polar bear scat.
The dog found many piles of scat, and the team analyzed the contents.Here, quinoa sniffs for scat on an ice flow.
Compared to the 1960s, the polar bear diet had changed. They now prey upon caribou, whose populations have boomed in the area
Here, a polar bear with a caribou carcass.
Because the polar bears come ashore earlier, they are now on land when lesser snow geese are nesting, and now eat goose eggs as well.