Keeping up with bats: dynamic auditory tuning in a moth.
Many night-flying insects evolved ultrasound sensitive ears in response to acoustic predation by echolocating bats . Noctuid moths are most sensitive to frequencies at 20-40 kHz , the lower range of bat ultrasound . This may disadvantage the moth because noctuid-hunting bats in particular echolocate at higher frequencies shortly before prey capture and thus improve their echolocation and reduce their acoustic conspicuousness . Yet, moth hearing is not simple; the ear's nonlinear dynamic response shifts its mechanical sensitivity up to high frequencies. Dependent on incident sound intensity, the moth's ear mechanically tunes up and anticipates the high frequencies used by hunting bats. Surprisingly, this tuning is hysteretic, keeping the ear tuned up for the bat's possible return. A mathematical model is constructed for predicting a linear relationship between the ear's mechanical stiffness and sound intensity. This nonlinear mechanical response is a parametric amplitude dependence that may constitute a feature common to other sensory systems. Adding another twist to the coevolutionary arms race between moths and bats, these results reveal unexpected sophistication in one of the simplest ears known and a novel perspective for interpreting bat echolocation calls.
Windmill
James Frederick Charles
JF
School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, United Kingdom. james.windmill@bristol.ac.uk
Jackson
Joseph Curt
JC
Tuck
Elizabeth Jane
EJ
Robert
Daniel
D
D000161:Acoustic Stimulation; D000818:Animals; D005075:Biological Evolution; D002685:Chiroptera; D004423:Ear / Q000502:physiology*; D004455:Echolocation / Q000502:physiology; D005260:Female; D006309:Hearing / Q000502:physiology; D008297:Male; D008962:Models, Theoretical; D009036:Moths / Q000502:physiology*; D011235:Predatory Behavior; D013016:Sound