Diving shrews -- heat before you leap

Jul 03, 2012
The researchers nicknamed the American water shrews they study the "silver bullet." Credit: Robert A. MacArthur

How does the world's smallest mammalian diver survive icy waters to catch its prey? A recent study of American water shrews to be presented at the Society for Experimental Biology meeting in Salzburg on 1st July has surprised researchers by showing that the animals rapidly elevate body temperature immediately before diving into cold water.

This behaviour is unexpected because lower body temperatures enable diving 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.

According to Professor Kevin Campbell of the University of Manitoba, who led the study, "This finding goes against prevailing regarding the physiology of divers. Divers, especially small ones, have always been expected to try to maximize their underwater endurance."

Campbell added that this behaviour indicates the shrews are optimising factors other than just dive duration. Given that they are highly proficient aquatic predators, an elevated body temperature presumably heightens foraging efficiency.

The researchers nicknamed the American water shrews they study the "silver bullet." Credit: Robert A. MacArthur

Large animal divers, like seals and , have been studied extensively, but these findings show that small diving animals deserve attention as well.

Life at the limit

Compared to other diving mammals, the shrews carry the least amount of oxygen under water and use it up the most quickly. Typical dives thus last only 5-7 seconds. Being so small also makes them lose heat the fastest.

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 continually feed to provide for their voracious appetites but have to contend with very short dive durations and the constant threat of ."

The reaction time of the American water shrew is 10-20 times faster than a human's. Credit: Robert A. MacArthur

Exactly how the shrews warm themselves is unknown. Often, the shrews elevated body temperature while they were simply 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.

As part of this study, the researchers observed the shrews' behaviour when diving into water of different temperatures. They compared the length of the shrews' dives in warm and and also monitored the shrews' before, during, and after dives.

Explore further: Chimpanzees prefer firm, stable beds

add to favorites email to friend print save as pdf

Related Stories

How water shrews find prey in the dark

Feb 07, 2008

Shrews are tiny mammals that have been widely characterized as simple and primitive. This traditional view is challenged by a new study of the hunting methods of an aquatic member of the species, the water ...

Sticky snack for elephant-shrews

Nov 16, 2010

Long-nosed Cape rock elephant-shrews are fond of sticky treats, according to Dr. Petra Wester from the University of Stellenbosch in South Africa. Her investigations show for the first time that the elephant-shrew, ...

Seals protect brain during icy dives

Oct 10, 2006

Norwegian scientists say they've determined seals cease shivering during long icy dives to conserve oxygen and, therefore, minimize brain damage.

Natural-born divers and the molecular traces of evolution

Jun 29, 2009

An aquatic lifestyle imposes serious demands for the organism, and this is true even for the tiniest molecules that form our body. When the ancestors of present marine mammals initiated their return to the oceans, their ...

Diving seabirds: Working hard and living long

Jul 02, 2012

Scientists have found that diving birds reach their 30s and then die quickly and suddenly, showing few signs of aging prior to death. Their findings, which will be presented at the Society for Experimental ...

Recommended for you

Chimpanzees prefer firm, stable beds

1 hour ago

Chimpanzees may select a certain type of wood, Ugandan Ironwood, over other options for its firm, stable, and resilient properties to make their bed, according to a study published April 16, 2014 in the open-access ...

Offspring benefit from mum sending the right message

9 hours ago

(Phys.org) —Researchers have uncovered a previously unforeseen interaction between the sexes which reveals that offspring survival is affected by chemical signals emitted from the females' eggs.

Lemurs match scent of a friend to sound of her voice

23 hours ago

Humans aren't alone in their ability to match a voice to a face—animals such as dogs, horses, crows and monkeys are able to recognize familiar individuals this way too, a growing body of research shows.

User comments : 0

More news stories

Chimpanzees prefer firm, stable beds

Chimpanzees may select a certain type of wood, Ugandan Ironwood, over other options for its firm, stable, and resilient properties to make their bed, according to a study published April 16, 2014 in the open-access ...

For cells, internal stress leads to unique shapes

From far away, the top of a leaf looks like one seamless surface; however, up close, that smooth exterior is actually made up of a patchwork of cells in a variety of shapes and sizes. Interested in how these ...

Down's chromosome cause genome-wide disruption

The extra copy of Chromosome 21 that causes Down's syndrome throws a spanner into the workings of all the other chromosomes as well, said a study published Wednesday that surprised its authors.

IBM posts lower 1Q earnings amid hardware slump

IBM's first-quarter earnings fell and revenue came in below Wall Street's expectations amid an ongoing decline in its hardware business, one that was exasperated by weaker demand in China and emerging markets.