11/10/2014 7:15:26 PM
From Hums to Scented Trails - How Polar Bears Communicate
We are sitting on the shores of the Hudson Bay, snug inside our Tundra Buggy®, scouting for any polar bears that may be nearby. Outside, the windy, overcast morning has given way to a crystal blue sky and glittering snow. We spy a polar bear in the near distance, and then another, and another and another! The crew on Buggy One buzzes with excitement, throwing on hats, parkas and gloves—gearing up to go on to the back deck to get a better view of the six polar bears that are close to us. The light couldn't be better, the polar bears couldn't be more beautiful, and we're sharing this view with the world through the Explore.org Tundra Buggy Cam.
Polar bears are largely solitary mammals, but they've developed, over the long course of their evolution, a flexible approach to socializing and communicating with each other in order to survive and reproduce. This means that the signals and cues that polar bears use for communication can take a variety of forms, depending on the context and stage of their life-cycle. Right now, the small group of bears within our view gives us a chance to see some examples of how these "solitary" bears navigate their social landscape while they are waiting for the sea ice form on the Hudson Bay.
Testing the Social Waters
At this time of year, in this region, polar bears can be found at quite high densities. The group surrounding our buggy now includes a mother and her yearling cub. This family is fearlessly "telling" a curious young male to keep his distance. As the mother charges and growls at him, her message is universally clear: stay away!
Other interactions between polar bears here may include young males sparring with each other. These monumental play-fights let males test their strength and agility. Ultimately, the sparring sessions provide information to individual bears about their competitive abilities in relation to other males in the population. This information can help guide decisions (as in, to fight or not to fight?) during competition for mates in the spring, when the breeding season is in full swing.
Scent Trails for Finding Mates
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.
Scent communication is something most people are familiar with. When you take your dog for a walk, you've probably noticed that it will stop numerous times to investigate the scent left by another dog at a fire hydrant or sign post. Polar bears, like many other solitary mammals, appear to use scent to communicate as well, but they use a slightly different strategy from many other animals. This is because their 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. But because this form of communication is tied to the sea ice, increased fracturing of the sea ice may leave these trails vulnerable to disruption—and breeding success may decrease as a result.
During the period of maternal care, acoustic communication is prominent, and the cubs appear do all the "talking." Bear cubs emit a range of vocalizations, especially while in the denning phase of their development, and bear mothers need to be able to interpret these sounds and attend to the needs of their dependent offspring. Among the most distinctive of these is the "hum," which is largely associated with nursing and is very loud. Other vocalizations are more plaintive and demonstrate needs related to hunger and warmth.
Because communication, regardless of its form, evolves in tandem to an animal's environment, rapid environmental change can render age-old communication strategies inefficient. Polar bears, of course, are experiencing extremely rapid and profound changes in their sea ice habitat, and the implications for their social dynamics may be profound. In particular, the scent communication they rely upon to find mates during the breeding season will be impacted as the sea ice breaks up.
We are incredibly lucky to have the opportunity to see so many polar bears in one place, doing what polar bears do. We hope that experiencing these bears up close and personal on the Polar Bear Cams will inspire people to increase their efforts towards reducing their carbon footprint—and to let world leaders know they want meaningful action. You can speak up for action by signing Polar Bears International's® Petition for Polar Bears.