July 5, 2012
Diving Shrews Warm Up Before Taking The Plunge
redOrbit Staff & Wire Reports - Your Universe Online
According to research presented July 1 at the Society for Experimental Biology meeting, American water shrews rapidly raise their body temperature just before diving deep into icy waters.This finding has surprised researchers because normally, lower body temperatures enable diving mammals to stay underwater for longer, so heating up doesn't make sense. This is because animals use up oxygen more quickly when they are warmer.
Lead researcher, Professor Kevin Campbell of the University of Manitoba, said: "This finding goes against prevailing dogma regarding the physiology of divers. Divers, especially small ones, have always been expected to try to get the most bottom time from their time underwater."
Campbell added that this behavior indicates the shrews are utilizing factors other than just dive duration. Given that they are highly proficient aquatic predators, an elevated body temperature presumably heightens food hunting efficiency. Large animal divers, like seals and penguins, have been studied extensively, but these findings show that small diving animals deserve attention as well.
As part of this study, the researchers observed the shrews' behavior when diving into water of different temperatures. They compared the length of the shrews' dives in warm and cold water and also monitored the shrews' body temperatures before, during, and after dives.
Compared to other diving mammals, the shrews carry the smallest amount of oxygen under water and use it up faster. Therefore typical dives last only 5-7 seconds. Being so small also makes them lose heat faster.
Dr Roman Gusztak, who participated in the study, said: "The shrews are likely surviving at the limits of what is possible for a diving mammal. They must always feed to provide for their voracious appetites but have to contend with very short dive durations and the constant threat of hypothermia."
Exactly how the shrews warm themselves is unknown. Often, the shrews elevate body temperature while they are sitting still at the water's edge before a dive. The researchers believe the shrews are shivering or using their brown fat to generate heat.