研究显示一些蝙蝠进化成“隐形战机”

2010/08/23 00:55:19

蝙蝠使用超声波回声定位，但它们捕食的一些飞蛾能感知到蝙蝠发出的超声波并据此躲避。英国一项最新研究说，一些蝙蝠因此又进化出了类似“隐形战机”的功能，可以改变所发出的超声波，让飞蛾难以察觉自己的存在。

英国布里斯托尔大学研究人员在新一期《当代生物学》（Current Biology）杂志上报告说，在蝙蝠与飞蛾之间长期的互动进化中，一些飞蛾已经可以感知到蝙蝠发出的超声波，从而躲避蝙蝠的捕食。但研究人员发现欧洲宽耳蝠仍然可以捕食到这些飞蛾，因此他们分析了这种蝙蝠发出的超声波。

研究人员发现，欧洲宽耳蝠在捕食飞蛾时会大幅降低所发出的超声波的振幅，与其他蝙蝠发出的高振幅超声波相比，其“安静”程度可提高约百倍。研究人员又在飞蛾耳中装入微小的探测器，记录它在听到不同超声波时耳朵神经的信号变化，结果也证实，其他种类的蝙蝠离飞蛾约30米时就会被飞蛾发觉，而具有“隐形”本领的欧洲宽耳蝠可逼近到3．5米还不被飞蛾察觉。

Less is more for a hungry bat

Press release issued 19 August 2010

Like a stealth fighter plane, the barbastelle bat uses a sneaky hunting strategy to catch its prey. A team of researchers from the University of Bristol combined three cutting-edge techniques to uncover the secret of this rare bat’s success.

Every night a battle between bats and their insect prey rages above our heads as bats call and listen for the echoes of their dinner.  Many moths have developed a special anti-bat defence; unlike us, they can hear the ultrasonic calls of bats and avoid an attack with evasive flight.

Until recently, it seemed that these moths had outmanoeuvred bats in this evolutionary arms race, but researchers from Bristol’s School of Biological Sciences have discovered that one special bat species (Barbastella barbastellus) has an unexpected counterstrategy to this defence: whispering.

The barbastelle bat is a very successful hunter which eats large numbers of moths.  However, the researchers did not know whether most of these moths were earless and thus unable to hear predators approaching, or whether the bats had found a way to catch moths that could hear them coming. 

While previous studies could only determine the types of insects the bats had eaten (beetles, flies, moths and so on), researcher Matt Zeale developed a method using a new set of genetic markers to identify the_ species_ of those insects.  This established for the first time that the barbastelle almost exclusively preys on moths that have ears. 

In order to find out why the barbastelle can catch such moths when other bats cannot, the researchers then measured how well moths can detect different bat species by recording the activity of the nerve in the moth’s ear while tracking the position of flying bats at the same time.  This happened in several locations around Bristol including a graveyard in Clifton.

Dr Hannah ter Hofstede said: “Recording from the ear of a moth in the field was a real challenge but it yielded some amazing results.  Whereas moths can detect other bats more than 30 m away, the barbastelle gets as close as 3.5 m without being detected.”

The researchers then analysed the barbastelle’s echolocation calls and found that they are up to 100 times quieter than those of other bats. 

Dr Holger Goerlitz said: “We modelled detection distances for bats and moths and found that by whispering, the barbastelle can hear the echo from an unsuspecting moth before the moth becomes aware of the approaching bat.  This advantage, however, comes at the cost of reduced detection range, similar to us trying to navigate in the dark using a lighter instead of a spotlight.”

The barbastelle bats’ strategy is successful as it enables them to catch moths that would normally fly away and to avoid competition by feeding on prey that other bats find much more difficult to catch.

Such success is unusual, Dr Goerlitz said: “It’s a rare case in evolution that a predator wins the arms-race with its prey because the predator only loses its dinner, but the prey loses its life.”

The research is published today in Current Biology.

Paper

‘An aerial-hawking bat uses stealth echolocation to counter moth hearing’ by Holger R. Goerlitz, Hannah M. ter Hofstede, Matt R. K. Zeale, Gareth Jones, Marc W. Holderied Current Biology