Until now, images of polar bears have not brought to mind a bear snacking on goose eggs. That may change with the reporting of Robert Rockwell, a research associate in ornithology at the American Museum of Natural History (AMNH), and graduate student Linda Gormezano in the magazine Polar Biology and other researchers’ observations.

While the polar bear is generally pictured on sea ice waiting for his favorite food, a seal, to appear, this hunting platform is melting away. Sea ice is breaking up earlier in the Arctic summer and not reforming as it did in the past decades. The polar bear is forced to move further north to pack ice and sometimes onto land. Young male bears between 2 and 5 years old, called subadult males, are especially at risk in the changing habitat. Adults drive the subadults from the best hunting territory, forcing them to live off stored fat reserves for months at a time.

According to an AMNH science news story, when bears move to the tundra, they may enter the nesting grounds of snow geese. “Over 40 years, six subadult male bears were seen among snow goose nests, and four of them were sighted after the year 2000,” Rockwell says. “I’ve seen a subadult male eat eider duck eggs whole or press its nose against the shell, break it, and eat the contents. This is similar to a different research group’s observations of polar bears eating Barnacle Goose eggs on Svalbard, an island near Norway.”

The goose eggs and embryos are a highly nutritious source of food for foragers. The good news for the hungry young bears is the increase in the goose population. Both bears and geese are coming to the Hudson Bay earlier in the year.

Rockwell and Gormezano calculated that the ice breakup and the hatching time will occur earlier each year, resulting in an overlap in over three years. This means that eggs could become a reliable food source for the bears.

How many eggs will the bear need to eat? The researchers say a bear would need to consume the eggs of 43 nests to replace the energy gained from the average day of hunting seals. Within a decade, because timing changes would put bears in contact with even more nests with younger, more nutritious embryos, a bear would only need to consume the eggs of 34 nests to get the same amount of energy.

Rockwell and Gormezano’s research article is currently available in the online version of Polar Biology.

Look for more about mammals in the polar regions in the January 2009 issue of Beyond Penguins and Polar Bears. You’ll find dozens of online resources, book lists, lesson plans, and science and literacy content knowledge for K-5 teachers.