Polar bears are increasingly foraging on seabird eggs as climate change shrinks their arctic hunting grounds, but research published yesterday on the phenomenon highlights the struggle the predators have to adapt to their rapidly changing environment.
Dwindling sea ice is cutting short the time they have to hunt seals, their preferred prey.
With a growing imperative to find alternative sustenance, polar bears have been pushed further afield in search of food, including scavenging in areas populated by humans.
Some are also coming ashore at the same time as seabirds are nesting to snack on their eggs.
To measure how efficient the bears were at this foraging — and therefore how useful the eggs are to provide energy in their diets — researchers in Canada used drones to monitor them feeding from common eider duck nests on Mitivik Island in Nunavut.
The study, published in the journal Royal Society Open Science, tracked how the bears approached the nesting site over 11 days as the number of eggs were depleted.
“We found that later-arriving bears increasingly visited more empty nests and did not travel in an energy-minimizing way, but became less picky in the clutches they consumed,” said lead author Patrick Jagielski, of the Great Lakes Institute for Environmental Research at the University of Windsor.
Bears also did not consistently realize that the sudden appearance of a fleeing eider hen meant that eggs were nearby.
“This study demonstrates that, while species are able to incorporate ‘less preferred’ resources into their diet when their primary prey becomes more difficult to obtain, they may not be able to do so efficiently,” the authors wrote.
Jagielski said that the research could not speak more broadly to polar bears’ ability to cope with climate change, but did raise questions about the energy value of eggs as an alternative food source.
There are approximately 25,000 Ursus maritimus left in the wild today in 19 population subgroups distributed across the arctic in Alaska, Canada, Greenland, Norway and Russia.
In July last year, a study published in Nature Climate Change estimated that the species would be starved to extinction by 2100.
Researchers looked at predictions for climate heating and data on the increasing portion of the year that the bears’ must survive on their fat reserves.
Earlier this month, a paper published in the journal Global Change Biology found that polar bears maintained highly specialized diets of soft blubber and flesh for hundreds of years — even during previous periods of arctic warming.
Researchers at Vanderbilt University, who examined dental wear in skulls held in museums, said that polar bears are so specialized in their diets that they might struggle to adapt in a warming arctic.
However, an increase in encounters with grizzly bears could provide one option, as the two species have produced offspring, they said.
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