Paws Have Non-slip Grip

Biological Strategy

Polar bear

AskNature Team

Image: Peter Halling Hilborg / Flickr / Some rights reserved

Move in/on Solids

To obtain needed resources or escape predators, some living systems must move on solid substances, some must move within them, and others must do both. Solids vary in their form; they can be soft or porous like leaves, sand, skin, and snow, or hard like rock, ice, or tree bark. Movement can involve a whole living system, such as an ostrich running across the ground or an earthworm burrowing through the soil. It can also involve just part of a living system, such as a mosquito poking its mouthparts into skin. Solids vary in smoothness, stickiness, moisture content, density, etc, each of which presents different challenges. As a result, living systems have adaptations to meet one, and sometimes multiple, challenges. For example, some insects must be able to hold onto both rough and slippery leaf surfaces due to the diversity in their environment.

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Protect From Ice

Freezing temperatures can be difficult for living systems to manage. They can cause ice crystals to form in blood and tissues, which causes damage to cells and ultimately, death. Living systems can’t afford the energy required to melt ice crystals, so instead, many have strategies to prevent crystals from forming in the first place. Many amphibians, plants, and insects have chemicals that act as antifreeze to prevent icy crystal formation. Another challenge ice presents is that it creates a slick surface, requiring friction to traverse. This is why polar bears’ paws have a rough surface that grips ice.

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Mammals

Class Mammalia (“breast”): Bats, cats, whales, horses, humans

Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.

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The paws of polar bears grip ice well due to the rough surface of their pads.

Image: Hannes Grobe 21:16, 12 November 2006 (UTC), Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany / Wikimedia Commons /

to be defined

Image: Ansgar Walk / Wikimedia Commons /

Image: U.S. Fish and Wildlife Service / Wikimedia Commons /

Image: en:User:Cburnett / Wikimedia Commons /

'''en:''' A Polar Bear floating at the <a href=http://commons.wikimedia.org/w/index.php?title=Henry_Doorly_Zoo&action=edit&redlink=1 class=new title=Henry Doorly Zoo (page does not exist)>Henry Doorly Zoo</a> in <a href=http://commons.wikimedia.org/wiki/Omaha,_Nebraska title=Omaha, Nebraska>Omaha, Nebraska</a>.

“A polar bear spends the winter living on sea ice—ice formed when the ocean freezes. But the bear has no trouble keeping its footing on slippery ground. Its paws are perfect for getting around on a slick, cold surface. Rough pads give it a nonslip grip, and thick fur between the pads keeps the bear’s feet warm. It uses the sharp, curved claws on its front paws like hooks to climb onto the ice from the water. Polar bears’ claws also help them dig in the ice when they hunt seals.” (Kranking 2001)

Last Updated October 16, 2016

References

Book

Bear Necessities: How Polar Bears Survive the Deep Freeze

Kathy Kranking

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