Otters are spectacular marine animals. They can hold their breath for up to eight minutes as they dive in search of prey, such as clams and crabs.
However, a mystery that scientists had not been able to decipher until now was how they managed to stay warm in the cold waters of the Pacific, deprived of the body fat that isolates other animals (such as whales and walruses).
The answer, according to a new article published in the journal Science , is a unique energy conversion system by which muscle tissue “filters” large amounts of heat throughout the body.
This is the main difference from other mammals, who must put their muscles to work through exercise or involuntarily shiver to achieve the same result.
Study development
The study’s principal investigator, Traver Wright, explained that while sea otters’ dense, waterproof fur makes up for heat loss, it is not enough on its own to cope with the frigid waters of Alaska, where most reside.
Scientists already knew that sea otters burn a lot of energy (about three times more than expected for mammals of their size), and to meet the demand, they can consume up to 25 percent of their body mass in one day.
However, it was not clear which tissues were making use of this energy and how it was going to produce heat.
To find out, the scientists took muscle samples from sea otters that were already dead or had been rehabilitated by the Monterey Bay Aquarium and were preparing for their release.
Then they used a device to measure oxygen consumption.
Generate heat without doing anything
In general, the main function of the muscles is to be able to move the body. However, in otters much of the energy produced by breaking down sugars and fats is used as heat rather than being used by the mitochondria to do work, such as promoting muscle contraction.
This helps them maintain a 37 degree body temperature in freezing conditions (outside). Similarly, scientists discovered that this thermogenic effect is present in animals since they are babies.
They also found no difference between animals in captivity and those raised in the wild.
