Bat alert

时间:2019-03-08 08:20:18166网络整理admin

By Matt Walker STUDYING bats could be forcing them to go hungry, warn researchers in Britain. Normally, two rings are used to study bats. A durable, metal ring with a serial number gives the animals a lifelong identity mark. And in short-term studies, researchers often add a second, coloured plastic ring so that they can work out who’s who at a distance. Both rings are clipped onto one of the forearms that supports each wing. Gareth Jones and his colleagues at the University of Bristol say these rings could be interfering with the bats’ feeding behaviour because they knock together, making a sound that scares away insects the bats feed on. The team was recording the echolocation calls of two species of mouse-eared bat, Myotis myotis and Myotis blythii, in the lab when they picked up strange ultrasonic noises from rings clashing on the bats. “We noticed it as an aside, really,” says Jones. “It is like an ultrasonic clonk.” Jones speculated that the sounds might be audible to moths that the bats eat. The moths have tympanic organs, drum-like hearing devices that are sensitive to ultrasonic frequencies. The team tested the theory by first checking the neural response of lesser yellow underwing moths,Noctua comes, to the ring sounds. Mouse-eared bats usually echolocate at night using ultrasound frequencies around 45 kilohertz. Moths can hear these calls, but the team found that the moth’s nerves respond even more sensitively to ultrasound at 20 kilohertz, which is close to the frequency produced by the clinking rings. Next the researchers played back the ring sounds to 33 flying moths. Nearly half the moths performed an elaborate escape manoeuvre on hearing the noise (Animal Behaviour, vol 57, p 741). “It might be dangerous to double-ring bats,” says Jones. “It’s equivalent to putting a cat bell on a cat. The sound alerts prey.” Previous research has shown that evasive manoeuvres give moths a 40 per cent better chance of avoiding being eaten. Jones expects that other prey insects could also detect the ring sounds. Bush crickets, for instance, may stop singing on hearing the noise, making it harder for bats to locate them. He doesn’t believe, however, that the ring noises would confuse the bats themselves. “Bats are good at filtering out sounds they are not interested in. They can work out their own echoes in a cave of hundreds of bats all echolocating at the same time.” Bat expert Paul Racey of Aberdeen University says the discovery is important. “Rendering bats less able to get food could have very serious conservation consequences.” It could also affect the results of studies into complex bat behaviour,