Staying warm while swimming in cold water isn’t easy for sea otters.
One way they keep from getting cold is by growing very thick fur. This two-layered fur has more than a million hairs per square inch. In comparison, humans have about 100,000 hairs per square inch on their heads.
By fluffing their fur, air bubbles are trapped increasing the hair’s ability to keep otters warm.
But fur only helps otters so much.
Scientists know that by moving around, muscles generate heat. That’s one reason you shiver when you get cold. Your body is trying to generate heat by moving your muscles.
"You mostly think of muscle as doing work to move the body," said physiologist Tray Wright, a research assistant professor at Texas A&M University. "When muscles are active, the energy they use for movement also generates heat."
Wright said that because muscle makes up a large portion of a mammal’s body, 40% to 50%, activity can warm the body up quickly.
Muscles can also generate heat without doing work by using something known as “leak respiration," Wright said. Leak respiration can do the same as when you shiver, without the shivering.
Sea otters also eat a lot to stay warm, up to a quarter of their weight, which provides fuel for their muscles. They eat a variety of seafood, including crabs, sea urchins, mussels and clams. Northern sea otters include fish in their diet.
Still unknown is how sea otters can turn up their body heat on demand. Their average body temperature is 100 degrees.
Sea otters can measure 4 feet long. Those living in the north — along the coast of Alaska and Washington — are about 20 to 30 pounds heavier than those living in southern waters along California’s central coast. The California population, estimated at about 3,000 animals, is considered endangered.
— Brett French, email@example.com