August 22, 2005 | David F. Coppedge

You Otter Hair How Otters Keep Warm

While on a sabbatical exploring Isle Royale National Park, John Weisel (U of Pennsylvania) decided to collect hair from various mammals.  He found otter fur to be particularly interesting, says a press release from U of Penn Health System.  Since otters don’t have a layer of fat, he wondered, how do they keep warm in the icy water?  Scanning electron microscopy showed the secret: the hairs fit together like tongue-and-groove woodwork: “They found that the cuticle surface structure of the underhairs and base of the less-abundant guard hairs are distinctively shaped to interlock, with wedge-shaped fins or petals fitting into wedge-shaped grooves between fins of adjacent hairs”  (emphasis added).  Click on the micrograph for additional photos and diagrams of how these hairs interlock.

Not much on a mammal’s body seems simpler than hair, but like everything else in living things, simplicity evaporates on closer inspection.  Not only are these hairs shaped just right to produce a tight, insulating pattern, but the blueprint has to be encoded in DNA and transcribed by the cellular construction factory according to spec, and extruded from each hair follicle at the right time, with the right shape, the right color and the right length.  Lecturer Dr. David Menton can keep an audience entranced for an hour about the wonders of hair.  The structural details on the micro level are necessary to produce the macro result: a sleek, playful otter that makes a living in cold water.  It doesn’t take much water to keep a daughter otter happy.  Two pints makes one cavort.

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Categories: Mammals

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