Listening for bats: the hearing range of the bushcricketPhaneroptera falcatafor bat echolocation calls measured in the field

Abstract

The hearing range of the tettigoniid Phaneroptera falcata for the echolocation calls of freely £ying mouseeared bats (Myotis myotis) was determined in the ¢eld. The hearing of the insect was monitored using hook electrode recordings from an auditory interneuron, which is as sensitive as the hearing organ for frequencies above 16 kHz. The £ight path of the bat relative to the insect's position was tracked by recording the echolocation calls with two microphone arrays, and calculating the bat's position from the arrival time di¡erences of the calls at each microphone. The hearing distances ranged from 13 to 30 m. The large variability appeared both between di¡erent insects and between di¡erent bat approaches to an individual insect. The escape time of the bushcricket, calculated from the detection distance of the insect and the instantaneous £ight speed of the bat, ranged from 1.5 to more than 4 s. The hearing ranges of bushcrickets suggest that the insect hears the approaching bat long before the bat can detect an echo from the £ying insect.

Echolocation and passive listening by foraging mouse-eared batsMyotis myotisandM. blythii

“…This is all the more true for M. blythii, whose diet largely includes tettigoniids that can hear ultrasound (Arlettaz et al, 1997b) and that may then evade capture by detecting the bat's calls early on (Schul et al, 2000;Schulze and Schul, 2001). Weak pulses can probably reduce this risk considerably, because prey will detect them too late to avoid capture.…”

Flight and echolocation behaviour of whiskered bats commuting along a hedgerow: range-dependent sonar signal design, Doppler tolerance and evidence for `acoustic focussing'

“…As flying bats were calling repeatedly, individual call-by-call localisations were strung together to reconstruct the bat's flight path (Holderied and von Helversen, 2003;Schul et al, 2000).…”

Sound signalling in orthoptera

“…Schul et al (2000) measured the hearing range of the long-winged bushcricket, Phaneroptera falcata, for echolocation calls of the mouse-eared bat Myotis myotis in the field. Male P. falcata often call from exposed perches on the vegetation and, while singing, frequently change position by flying, so they are exposed both to aerial-hawking and foliage-gleaning bats.…”