Wikimedia Commons
“ There are certain principle that one must abide by in ordering to successfully survive a horror movie , ” Randytold usinScream . “For instance , Number One : you’re able to never have sex . Sex equalise death , OK ? ”
He ’s right . For some reason , sex often draws out slasher movie villain , and when suffer character snitch up , they often also get chop up . The connection between sex and end is n’t just a repulsion movietrope , though . biologist have often suggested that animals are at a higher risk of exposure for getting pop and run through during conjugation , either because they ’re more blatant , less vigilant , or ca n’t escape as fast .
For flies , it ’s that first factor that ’s the trouble . conjugation can mean sure doom because the sounds they make catch the attention of a killer lurking in the shadow .
In Europe , Natterer ’s bat ( Myotis nattereri ) often roost in barn and cow sheds , draw and quarter by flies that are appeal to animal manure . There ’s mass to eat , but catching the flies is n’t easy . Natterer ’s bats Leigh Hunt by echo sounding , generate ultrasonic call and using the replication that take a hop back to find quarry and map their milieu . Inside the farm buildings , finding flies this way is “ almost insufferable , ” says biologist Stefan Greif , because the faint reverberation made by the fly are block out by the more monolithic single bouncing back from the wall and roof . What ’s more , the fly ball also stop flying around at night , when the squash racquet hunt , and either move around by walking or model still on the ceiling , making them even harder detect .
Over four years , Greif and his squad of researchersfilmedthousands of fly walk along the ceiling of a moo-cow shed in Weitershausen , Germany that was home to a dependency of 45 bats . In all that time , not one of them was attacked by a at-bat . Yet , the bats outride , and Greif be intimate that flies made up the absolute majority of the mintage ’ diet . So how were they catching bug that were all but invisible to them ?
It turns out that the bats are a short morsel like B - movie killers , and make their attacks when the flies are having sexual urge . While tent flap just walk around were inconspicuous , Greif found that ones that were getting it on were a clear sonic target . This is because when flies twin , the male person flutter their wings , producing a burst of click - similar noises . Humans can hear the lower relative frequency noises as a soft buzz , while the high ones ring as loud and vindicated to the cricket bat as a dinner bell . More than a fourth part of the mating fly that Greif caught on photographic camera during the subject area were assail by the bat , and more than half of those flak were successful , with the squash racket devouring both tent flap in all but two cases .
To make certain that it was the sounds of sexual practice that have the bats ’ attention , the researchers tried two experiments . First , they stuck dead fly together in mating posture and mounted them on the ceiling . These were ignored by the bats , so it is n’t the bigger butt and larger sound reflection that mating flies make that gives them aside . When the scientists record the tent flap ’ mating go in the second experiment and bring them back over a sound system , though , the bats go on the Leigh Hunt . The research worker watched as “ the bat go about , hovered and inspected the speaker , and in several case tried to reap the acoustically simulated flies from the speaker with their tail membrane — just as they did with veridical pairs of copulating fly front on the roof . ”
