Toronto: How does the world’s tiniest mammalian diver survive icy waters to catch its prey? By doing an instant warm-up exercise before diving into cold water, say researchers.
This behaviour is unexpected because lower body temperatures enable diving mammals to stay underwater for longer. Heating up doesn't make sense as animals use up oxygen more quickly when they are warmer, says Kevin Campbell, who led the study.
"This finding goes against prevailing dogma regarding the physiology of divers. Divers, especially small ones, have always been expected to try to maximise their underwater endurance," says Campbell, professor of physiology at the University of Manitoba, Canada.
He adds that shrews are highly proficient aquatic predators, an elevated body temperature presumably heightens foraging efficiency, according to a Manitoba statement.
Compared to other diving mammals, shrews carry the least amount of oxygen under water and use it up the most quickly. Typical dives thus last only five to seven seconds. Being so small also makes them lose heat the fastest.
Roman Gusztak, study co-author, said: "The shrews are likely surviving at the limits of what is possible for a diving mammal. They must continually feed to provide for their voracious appetites but have to contend with very short dive durations and the constant threat of hypothermia."
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism, defined as 35 degrees Celsius. These findings were presented at the Society for Experimental Biology meeting in Salzburg, Austria.
First Published: Thursday, July 05, 2012, 12:59