Arctic
polar bears may be adjusting their eating habits as their sea ice
habitat melts and the furry white predators stand to lose the floating
platform they depend on to hunt seals, their primary food. According to
researchers, however, the bears are displaying flexible eating habits as
their world changes around them.
Indeed, scientific studies indicate
polar bear populations are falling
as the sea ice disappears earlier each spring and forms later in the
fall. But a series of papers based on analysis of polar bear poop
released over the past several months indicate that at least some of the
bears are finding food to eat when they come ashore, ranging from bird
eggs and caribou to grass seeds and berries.
"What our results suggest is that polar bears have flexible foraging strategies,"
Linda Gormezano, a biologist at the American Museum of Natural History in New York and a co-author of several of the papers, told NBC News.
Robert Rockwell / American Museum of Natural History
Quinoa,
a Dutch shepherd who was trained to sniff out polar bear scat, sits
next to find. Analysis of the polar bear scat reveals the animals have a
flexible foraging strategy.
The results stem from
research in western Hudson Bay, near Chruchill, Manitoba, Canada, which
is in the southern extent of polar bear habitat and serves as a
harbinger of what the animals are likely to face throughout their Arctic
range as the climate continues to warm and sea ice breaks up earlier
and earlier each spring.
The flexible foraging strategy of polar
bears "means that there may be more to this picture in terms of how
polar bears will adjust to changing ice conditions" than indicated by
models based on the spring breakup date of the sea ice and thus their
access to seals, Gormezano said.
She added that nobody knows for
sure how well polar bears will adapt to the changing food supply, but a
big step toward an answer is to study what they eat on land "rather than
assume that they may just be fasting."
Let them eat car parts
In addition to berries, birds and eggs,
Andrew Derocher,
a University of Alberta polar bear biologist who was not involved with
the recent studies, said people have seen a polar bear drink hydraulic
fluid as it was drained out of a forklift, chomp the seats of snow
machines, and eat lead acid batteries.
"Polar bears will eat
anything," he told NBC News. "The question is: Does is it do them any
good? And everything we can see from what bears eat when they are on
land is it has a very, very minimal energetic return relative to the
cost."
Gormezano said the plants found in any given pile of poop
were usually the same, suggesting the bears eat whatever they find in
their immediate surroundings — they don't spend a lot energy searching
for food. Mothers and cubs, who wander farthest inland, feast on berries
found there. On the coast, where adult males linger, the poop is
predominantly shoreline grass seeds.
Animal remains, however,
showed no pattern, which fits with a landscape rich with nesting birds
and caribou and polar bears opportunistically eating whatever crosses
their path, according to a paper Gormenzano and colleague Robert
Rockwell published in
BMC Ecology in December 2013.
In a paper published in
Polar Biology
in May 2013, the researchers report observations of polar bears chasing
and capturing snow geese with the efficiency of a skilled hunter —
snagging one right after the other.
Robert Rockwell / American Museum of Natural History
A
polar bear eats a caribou on land. Recent studies suggest polar bears
have a flexible foraging strategy, which help them survive as they come
ashore earlier due to melting Arctic sea ice.
"Previously,
it had been thought that that would not be a very energetically
profitable thing for a polar bear to do because they expend more energy
in the chase than they get from consuming the food," Gormezano noted.
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