Polar Bears Have Smelly Feet

Posted Dec. 11th, 2014 by Melynda Harrison

Recently, scientists have discovered that polar bears have smelly feet. Not sweaty-gym-socks-smelly, but scent-trail-smelly.

Turns out polar bears paws leave a chemical trail wherever they go. Other polar bears can glean information from those scent trails.

Megan Owen, research scientist for the San Diego Zoo Institute for Conservation Research, wrote for Polar Bears International, “Of course, finding a mate in the vast Arctic, where an individual bear can range over 600,000 square kilometers, is challenging and requires a quite different approach to communication. New research shows that polar bears will “follow their nose” to find an appropriate mate.”

Dr. Megan Owen on the back of Buggy One.

Dr. Megan Owen on the back of Buggy One.

Owen, and colleagues from Polar Bears International and the US Geological Survey, published results in the Journal of Zoology.

Dr. Don Moore, Dr. Megan Owen, Dr. Cecilia Bitz, Dr. Andrew Derocher and BJ Kirschhoffer.

Dr. Don Moore, Dr. Megan Owen, Dr. Cecilia Bitz, Dr. Andrew Derocher and BJ Kirschhoffer on the back of Buggy One after a season of Tundra Connections for Polar Bears International

The researchers took samples from paw prints in the snow and ice around the southern Beaufort and Chukchi Seas in the Arctic Ocean, resulting in scent samples from 203 wild polar bears.

Katrina Knott, research assistant for USGS, swabs the inside area between a female polar bears toes. It's thought that female polar bears possibly give off a scent through their feet during estrus. Kaktovik, Alaska.

Katrina Knott, research assistant for USGS, swabs the inside area between a female polar bears toes. It’s thought that female polar bears possibly give off a scent through their feet during estrus. Kaktovik, Alaska.

The scents were offered to ten male bears and sixteen females in zoos across North America. The polar bears were all adults, with some being wild-born and others captive-born.

One of the tests subjects takes time off from work to play with a ball at the San Diego Zoo polar bear exhibit.

One of the tests subjects takes time off from work to play with a ball at the San Diego Zoo polar bear exhibit.

The zoo bears were more attracted to scents left by wild bears in the spring, and to bears of the opposite sex. Males were especially interested in female bears in oestrus.

A polar bear wanders the ice of the Beaufort Sea in search of a female.

A polar bear wanders the ice of the Beaufort Sea in search of a female.

The BBC reported, “The researchers also examined the feet of polar bears and found prominent sweat glands within the paws of two females. Other mammals are known to use similar sweat glands to communicate information about their territory and sexual or reproductive status. It may also be that the bears use their feet to tread urine into the ground and ice, marking their trails that way.”

Others species of bears mark vertical surfaces, including tree trunks, rubbing their bodies or anal glands to lay down scent.

The weight of a polar bear compacted the snow on this frozen lake. Surrounding snow was blown away by the wind to create these tracks on the icy.

The weight of a polar bear compacted the snow on this frozen lake. Surrounding snow was blown away by the wind to create these tracks on the icy.

The polar bears’ “…sea ice home lacks the landscape features that would typically be used as scent markers. Instead, polar bears appear to communicate with every step they take, leaving enough scent behind in their paw prints to provide some identifying information to other bears,” wrote Owen.

Steve Amstrup, another author on the paper and chief scientist for Polar Bears International said, “This paper confirms that polar bears have evolved the ability to detect differences in pedal secretions. We don’t yet know, with certainty, that they use this ability for communication purposes. But given the reliance of all bears on their sense of smell and the evidence that other species of bears do use scent for intra-species communication, it is entirely reasonable to postulate that the abilities shown in this paper evolved for communication purposes.”

Steve Amstrup and Geoff York, Polar Bears International biologists, taking field data from an immobilized large male polar bear on the Beaufort Sea.

Steve Amstrup and Geoff York, Polar Bears International biologists, taking field data from an immobilized large male polar bear on the Beaufort Sea.

According to the journal article, the results suggest that paw-scents convey information that may facilitate social and reproductive behavior, and that adaptation of chemical communication in polar bears has been shaped by the environmental constraints of their habitat.

So, what happens to polar bear trails as sea ice shrinks?

“The spring sea ice is far less extensive than it was historically. In addition to a general retreat, I saw sea ice character change dramatically during the 30 years I did polar bear research in Alaska,” said Amstrup. “It is more active and more fragmented, broken up like a jig-saw puzzle, than it used to be. Such fragmentation can only worsen as the world warms, and any scent trails left on the ice will become more fragmented. Increasing fragmentation can only make trails more difficult to follow.”

Polar Bear tracks crossing broken ice in the Beaufort Sea. Arctic Ocean.

Polar Bear tracks crossing broken ice in the Beaufort Sea. Arctic Ocean.

“The abilities shown here were most likely developed for communication through scent trails. Therefore, communication, including the ability of polar bears to find mates, may be compromised by the ongoing retreat and fragmentation of the sea ice,” Amstrup continued. “Retreating sea ice has been linked reduced foraging success because polar bears catch their prey from the surface of the sea ice.  This study shows another way sea ice changes may negatively impact polar bears.”

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