A polar bear leaves a trail of paw prints on the sea ice.

New research suggests that polar bears leave scented trails on the sea ice with each step they take, serving as signals to other polar bears.

© Daniel J. Cox/Natural Exposures

11/3/2014 2:04:21 PM

New Research Explores Scent Communication in Polar Bears

(November 3, 2014) - One of the enduring mysteries about polar bears is how males and females manage to find each other during the spring breeding season, given that the bears are largely solitary animals with home ranges covering up to 600,000 square kilometers. Scientists have long speculated that polar bears, like other bear species, use chemical signaling to find (or avoid) each other. But while brown and black bears, leave scent markings by rubbing against vertical objects like trees, the polar bear's sea ice habitat is in constant motion and has no such permanent features. Instead, new research suggests that polar bears leave signals for other bears with each step they take. This form of "scent trail" communication, likely shaped by their extensive travels over sea ice, may be at risk in a warming Arctic. As warmer temperatures disrupt the sea ice, the chemical trails polar bears have left there will become increasingly fractured and difficult to follow.

A new study led by Dr. Megan Owen of the Institute for Conservation Research, San Diego Zoo Global, along with scientists from Polar Bears International and the U.S. Geological Survey's Alaska Science Center, investigated the role of scent communication in polar bears. The scientists published their results on November 3, 2014 in the Journal of Zoology, London (M.A. Owen et al: An experimental investigation of chemical communication in the polar bear, Journal of Zoology, 2014, DOI 10.1111/jzo.12181).

"Scientists studying wild polar bears have seen the bears sniff paw prints on the sea ice," said Dr. Owen. "They assumed the bears were assessing the scent left behind by their fellow bears. But to our knowledge, our study was the first to investigate the information they might be getting from the scent."

Owen and her team worked with both zoo bears and wild bears in conducting a study, exploring whether polar bears could discriminate between pedal scents collected from bears of the same sex, the opposite sex, and females of differing reproductive status. Because polar bear breeding is limited to the spring, they also investigated whether bears had different reactions to scents found on bear's feet at different times of the year.

Scientists with the U.S. Geological Survey swabbed the feet of wild polar bears as part of their fieldwork in Alaska on the Chukchi and Beaufort seas. These samples were then presented in controlled settings to 26 polar bears in zoos.

The researchers found the female polar bears were seasonally motivated to explore scents from the opposite sex. They also discovered that male polar bears could discriminate between the scents of males and females, and could also distinguish females in differing reproductive states.

"This is fascinating new research that suggests scents deposited when polar bears simply walk over the sea ice may play a role in the polar bear's social and reproductive behavior," said Dr. Steven Amstrup, chief scientist of Polar Bears International. "However, this method of communication, which may be instrumental in helping polar bears find their mates, may be at risk in a warming Arctic, as scent trails increasingly are broken up by melting ice." 

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