The world's smallest diving mammals, water shrews, apparently have a
unique talent that allows them to survive diving in icy water. They seem
to have the ability to quickly raise their body temperature before
submerging themselves in water in search of such tasty tidbits as
aquatic insects, small fish, tadpoles, snails, and slugs.
Scientists are baffled by this behavior since lower body temperatures allow diving mammals remain under water longer. Therefore this idea of pre-heating challenged their basic knowledge -- that warmer body temperature use up oxygen faster. They should be trying to increase their endurance under water. Why, then, would shrews trade off oxygen for body heat?
A recent study indicated that the shrews may be may be maximizing other factors in the dives rather than the expected duration. Since they are very efficient predators, researchers are presuming that this may support foraging.
Being so small, the shrews carry the least amount of oxygen and lose heat quickly. The average dive lasts just five to seven seconds. With a voracious appetite, they must dive frequently, and live pressing the envelope on the limits of survival.
Just how the shrews are managing this sudden rise in temperature is still a mystery. Scientists think that they may use shivering or their brown body fat for the increase. More research still needs to be done to understand this phenomenon.
Source: Science Blog