Their observations revealed that the tiny animals can catch prey just as quickly and efficiently at night as they do during the day and determined that they use three basic methods to do so. Working in darkness, water shrews:
Catania had discovered the third of these methods the shrews ability to follow scent trails underwater by exhaling air bubbles and then re-inhaling them in a 2006 study published in the journal Nature. This ability allows diving water shrews to literally sniff out the general location of underwater prey.
In the current paper, the researchers discovered that the water shrews use two additional methods to zero in on toothsome targets. They use their sensitive whiskers to determine the shape of objects that they encounter. And they are acutely sensitive to sudden water currents like those generated when a fish or insect attempts to swim away.
This combination of methods poses a serious conundrum for prey, Catania observes. If they freeze, they risk detection from touch or olfaction. But, if they try to swim away, they generate water currents that can reveal their location.
After observing the water shrews natural hunting behavior in nearly total darkness, the researchers devised a series of experiments to identify the specific detection methods that the tiny hunters use and to rule out some others.
By recording audible and ultrasonic calls, the researchers were able to rule out the possibility that the tiny shrews use sonar, echolocation or electrical sensitivity (electroreception) to find prey.
To test water shrews
|Contact: David F. Salisbury|