【英语时差8,16】鼩的吱吱声（在线收听）

Why Shrews Twitter Small mouse like mammals, shrews are not actually rodents or even closely related. Shrews are noisy little creatures– constantly twittering and squeaking as they scramble through their habitat. But why? All that noise could surely attract the attention of predators, so there must be an important reason for their endless twittering. One possibility is that shrews use calls for communicating with neighbors or mates. But some researchers have hypothesized that the twittering serves a totally different function– echolocation. Since shrews have poor eyesight, listening to the way their calls echo back from the surroundings might help them navigate through their environment. A team of German biologists reasoned that if calls were used solely for communication, then calling behavior should change depending on the presence or absence of other shrews. But if calls were used for echolocation, calling should change in response to changes in the physical surroundings rather than social situations. The researchers discovered that the twittering of shrews did not change in response to the simulated presence or absence of other shrews. But when the researchers changed the thickness of the straw bedding in the shrews’ enclosures, the rate of twittering changed too. This suggests that shrews may use their calls as a simple type of echolocation, and not only for communication. The echoes from their calls help them navigate in the dark and avoid obstacles in their path. Although more research is needed to understand how shrews use their twitter calls in the wild, the discovery is exciting news since shrews are one of the first land animals that might use echolocation.