Polar bears have been photographed scaling near vertical cliffs and feeding on thick-billed murre chicks and eggs. The startling pictures released by scientists show the dare devil bears climbing the cliffs on Coats Island, Nunavut, Canada.
Researchers from Canada have published a study looking at whether early ice break-up, linked to climate change, has increased predation on breeding birds such as snow geese (Chen caerulescens) and cliff nesting thick-billed murres (Uria lomvia).
In 2000 and 2003 researchers witnessed bears decimating the murre colony by eating chicks and eggs. The scientists, who have been studying this site since the 1980s, have not witnessed this behaviour before.
Polar bears prey on ringed seals. In many regions this single species makes up the majority of the bears' diet.
The researchers believe these bears are probably being "opportunistic" or perhaps looking for new food sources in desperation when there is lack of food elsewhere.
Thick billed-murres nest in dense colonies numbering tens or hundreds of thousands of individuals. The birds lay a single egg in late June or July and incubate for approximately 33 days. Researchers scale the cliff to ring the birds for their research.
The cliffs at Coats island, which are home to the bird colony, are almost vertical. The bears exhibit great skill in scaling the cliffs, which scientists previously believed were a relatively safe and "bear-free" habitat for the birds.
Traditionally, it was believed that bears ate relatively little and relied on stored fat while they were on land. But they are curious and opportunistic animals and always search for ways to supplement their diet.
As the ice-free season grows longer, the nutritional stress of a longer fasting period takes its toll, say researchers. In western Hudson Bay, for example, a longer ice-free season has been linked to lower reproductive success and lower survival.
The Arctic environment is changing. Studies report that an advanced timing of ice break-up and a longer ice-free season are creating problems for bears at the southern edge of their range.
Polar bears are highly adapted for hunting on sea ice and even though they may find opportunities when food sources present themselves, they are ill equipped to cope with longer ice-free seasons.
The study was undertaken by Dr Paul Smith, Dr Anthony Gaston and Dr Grant Gilchrist from the National Wildlife Research Centre Ottawa, Canada and Kyle Elliot from the University of Manitoba, Winnipeg, Canada.
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