HIGH DUTY CYCLE ECHOLOCATION AND PREY DETECTION ABILITY IN BATS

Abstract

While most echolocating bats separate pulse and echo in time (low duty cycle bats), a few species separate pulse and echo in frequency (high duty cycle). The type of écholocation is defined by the pattern of signal emission, but many other call variables differ significantly between the two approaches. This study used two complementary experiments to understand the role of flying prey detection ability as a selective force that could explain the diversity of écholocation behaviour in extant bats. I collected data from acoustical measurements of artificial sonar echoes from fluttering targets, and field recordings of hunting behaviour of different bat species. I found that prey detection is improved with increased pulse length and duty-cycle of écholocation calls. Proportionally, high duty cycle bats approached fluttering targets more often (18.6 %) than low duty cycle bats (1.16 %). Pulse length used by low duty cycle bats is limited by functional constraints of their auditory system. The frequency used by a given bat species cannot be explain by prey detection ability. High and low duty cycle bats are syntopic in some habitats, despite the fact that high duty cycle bats are more efficient at detecting flying prey than low duty cycle bats. Competition for flying insects as a food resource does not seem to be shaping the bat assemblage