The team tracked nine solitary female polar bears over 8-12 days
High-tech collar tracking collars on
nine female polar bears have measured the animals' efforts to find food
on the diminishing Arctic ice.
The collars recorded video,
locations and activity levels over 11 days, while metabolic tracers
allowed scientists to work out how much energy bears used.
This revealed that the animals were unable to catch enough prey to meet their energy needs.
The team say wild bears have higher metabolic rates than thought.
Moreover,
climate change appears to be having dramatic effects on the Arctic sea
ice, forcing polar bears to move greater distances as they hunt, and
making it harder for them to catch prey.
The vision of a polar
bear plucking a vulnerable seal off an ice floe is something familiar to
wildlife documentary fanatics. Earlier this winter though, an image of
an emaciated polar bear went viral, with many asking if this was the
telltale image of climate change.
The authors of this study,
published in the journal Science, point out that the animals do now need
to travel further to find seals, and that this is likely to be an
"important factor explaining declines in their body condition and
survival" of polar bears.
Tracking every move
Polar bears have to travel further to hunt as Arctic sea ice shrinks
In
Spring of 2014, 2015, and 2016, Anthony Pagano, a researcher at the
University of California Santa Cruz and his colleagues, set out to track
the polar bears' hunting and survival during this critical season. They
captured nine females on the sea ice of the Beaufort Sea and measured
the metabolic rates of each bear using blood and urine samples.
They also fitted the bear with the GPS-camera collars, to record and film their activity.
"We
found that polar bears actually have much higher energy demands than
predicted. They need to be catching a lot of seals," Mr Pagano
explained.
Arctic is decreasing at a rate of 14% per decade,
which is likely reducing polar bears' access to seals. And their plight
could be exacerbated by the need to alter hunting strategies with the
seasons.
In the spring, the researchers explained polar bears are
mostly preying on juvenile seals. But later in the year, after the
bears' long summer fast, those young seals are older and wiser, meaning
polar bears are not able to catch as many.
"It's thought that
bears might catch a couple per month in the fall, compared to five to 10
per month in the spring and early summer," Mr Pagano said.
"We
now have the technology to learn how they are moving on the ice, their
activity patterns, and their energy needs, so we can better understand
the implications of these changes we are seeing in the sea ice
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