Tiny “fingers” help polar bears grip.
like the rubber nubs at the bottom of a baby’s socks, Microstructures on bear paw pads To provide some extra friction, scientists on Nov. 1 journal of the royal society interfaceThe mat’s protrusions prevent polar bears from slipping on snow, says polymer scientist Ali Dhinojwala of the University of Akron in Ohio. The stickiness of gecko feet (Serial Number: 8/9/05).
Akron-based materials scientist Nathaniel Orndorf, who focuses on ice, adhesion and friction, is intrigued by the work the Dhinojwala lab is doing on geckos, but “we can’t really put geckos on ice,” he said. So he turned to polar bears.
Working with Dhinojwala and now animal biologist Austin Garner of Syracuse University in New York, Orndorf compared the claws of polar bears, brown bears, American black bears and sun bears. All but sun bears have raised paw pads. But polar bear bumps look a little different. The team found that their bulges tended to be taller for a given diameter. Experiments with 3D-printed bump models show that the extra height translates into greater traction on the lab-made snow.
Dhinojwala said that until now, scientists didn’t know that bump shape affects grasping and sliding.
The polar bears’ paw pads, which are also surrounded by fur, are smaller than those of other bears, an adaptation that may allow arctic animals to maintain body heat while stepping on ice, the team reports. Smaller pads generally mean less room for grip. So extra grip pads help polar bears make the most of what they have, Orndorf said.
In addition to the bumpy mats, the team hopes to study polar bears’ furry claws and short claws, which may also allow the animals to skid.