picture courtesy of Jimmy's otter page

Sea Otter Fur
 
 
 

Unlike other marine homeotherms, sea otters do not have a layer of blubber for insulation.  Instead, they possess a thick fur coat.  Although their fur coat is less insulative in air than many terrestrial animal's fur coats, it is sufficiently insulative in water.  In one experiment, the insulative properties of a snowshoe hair and a sea otter were compared.  The snowshoe hair has what is considered "very good" insulation from their coat in air while the sea otter's is considered only fair.  However, when the two were immersed in water, the snowshoe hare's fur increased conductance ten-fold, while the sea otter's only increased two-fold.  (Morrison, et.al, 1974)

Sea otter fur consists of three types of fur; primary guard hairs, secondary guardhairs and underhairs.  The guard hairs are stiff and long while the underhairs are shorter and wavy.  The guard hairs help stabilize the underhairs and "minimize disruption of the underhairs."   The underhairs make up a majority of the sea otter's coat. (Tarasoff, 1974)

The underhairs provide the insulation. Underhairs overlap and intertwine, creating a web to trap air bubbles.  The trapped air then reduces water exposure to the skin which greatly decreases heat loss to conduction.  This layer of air provides a barrier between the skin and the water.  Thus, heat loss due to convection is greatly reduced.  Furthermore, the waviness of the underhairs keeps the air bubbles small, minimizing heat loss by conduction and convection currents more. (Tarasoff, 1974)

 

Sea otters also use grooming to maintain the insulation value of their fur.  Grooming behaviors prevent the fur from becoming soiled which can reduce the underhairs ability to entrap air.  Grooming also helps to aerate the fur in conditions which sea otters cannot return to dry land to dry off.  (Tarasoff, 1974)

 

Soiling of the fur is one of the major causes of sea otter mortality after an oil spill.

 

main page  habitat thermoregulation metabolism other physiological adaptations behavioral adaptations oil spills and sea otters references