Sea Otters Fur Background
Share the following information with students:
Otters don't live in the air as we do. The down vest tested in Step 2 would keep them warm as long as it had a waterproof outer layer because down works by trapping air between feathers. The air-filled balloon is both waterproof and uses air as a fairly successful insulator. In Glacier Bay human divers use dry suits made of neoprene that trap a layer of air between their skin and the suit when diving in the Bay's cold waters. Otters also have a unique and very effective "covering" to keep them warm beneath the frigid waters of Glacier Bay.
Have students read about sea otter's fur, using the Resources
below so that they can explain how otters' fur keeps them warm and dry in the frigid water in which they live. Then ask students to:
Describe the sea otter's fur, both the outer coat and underfur. Include color(s), measurements and density.
Answer: The underfur ranges from brown to almost black. Guard hairs on top may be black, pale brown or silver. Fur on the head is usually buff or even white. The otter's guard hairs are 34 mm. to 36 mm in length; the underfur is 19 mm. to 20 mm. Adults' fur has an estimated 650,000 to 1,000,000 hairs per square inch.
Explain the reason why the sea otter’s fur is able to insulate the animal from extreme cold.
Answer: Since sea otters do not have a heavy layer of blubber to protect them from the cold they must depend on air trapped in their fur to maintain body temperature. Clean guard hairs are waterproof, protecting the underfur, which traps a layer of air to provide insulation. The use of air as insulation is very efficient, providing four times the insulation of the same amount of fat or blubber.
Explain why sea otters are constantly grooming their fur.
Answer: If the sea otter's fur becomes soiled or matted by materials, such as oil, the insulation qualities are lost. This results in loss of body heat and eventual death.