Polar bears find mates with scratch'n'sniff footprints

The scents polar bears leave behind while trudging through the Arctic snow are a treasure trove of information to other bears sniffing them. In the wild, polar bears follow specific tracks of individuals they want to meet, like a potential mate, and use scent as a clue to avoid bears that might hurt them or compete with them for food. They are most interested in tracking other individuals during the spring mating season.

But researchers say the changing Arctic climate may threaten this process and further endanger the species.

Scientists at the San Diego Zoo Institute for Conservation Research found that polar bear paws were full of scent-producing glands. The paws can also shed DNA and traces of urine, which is a signal used by some species of bears to identify themselves.

For a new study, published in the Journal of Zoology, they collected scent samples from the feet of various bears in the wild: male or female, with some females receptive to mating and others not. To get the scent, scientists spent five years swabbing between the toes of sedated bears. Swab samples were frozen and stored.

Bears in 10 American zoos, mostly wild-born, then got to sniff the foot odors smeared on a piece of cardboard through holes in a wooden box. Zookeepers did not want their bears to be able to lick the swabbings, because they might contain pathogens.

The scientists noted that in the spring, males have to fight against other males to mate with females "with location of mates as the first phase of competition and direct male-male contest competitions as the second phase." Zoo males they tested in the spring were very interested in the foot-pad scents of females ready to mate.

Conservationists worry that as the climate warms and sea ice fractures and diminishes, polar bears will lose track of each other, making it harder to find potential mates in the wild. And without understanding what makes one polar bear attractive to another, captive breeding programs are unlikely to succeed.