Tiny “fingers” can help polar bears get a grip.
The rubbery bottom of baby socks is a good example. microstructures on the bears’ paw padsScientists report that there is some friction added to the November 1 report in the Journal of the Royal Society Interface. Ali Dhinojwala (a polymer scientist at Ohio’s University of Akron) believes that the pad protrusions could prevent polar bears slipping on snow. The sticking power of gecko feet (SN: 8/9/05).
Nathaniel Orndorf, a materials scientist at Akron who focuses on ice, adhesion and friction, was interested in the work Dhinojwala’s lab did on geckos, but “we can’t really put geckos on the ice,” he says. He decided to look into polar bears.
Orndorf collaborated with Dhinojwala, Austin Garner (an animal biologist at Syracuse University in New York) and compared the paws polar bears to brown bears, American black bears, sun bears, and American black bears. Except for the sun bear, all paw pads had bumps. But the polar bears’ bumps looked a little different. The team discovered that their bumps are generally taller for a given diameter. This extra height results in more traction when using lab-made snow, as 3-D printed models suggest.
Until now, scientists didn’t know that bump shape could make the difference between gripping and slipping, Dhinojwala says.
Polar bear paw pads have a fur ring and are smaller than others. These adaptations may help Arctic animals to conserve heat while they tread on ice. The area available for gripping the ground is less with smaller pads. So extra-grippy pads could help polar bears make the most of what they’ve got, Orndorf says.
Along with bumpy pads, the team hopes to study polar bears’ fuzzy paws and short claws, which might also give the animals a nonslip grip.
