J Comp Physiol A (1987) 161:267-274 Journal of Sensory, Comparative .~,, and Physiology A Behavioral Physiology 9 Springer-Verlag1987 The echolocation and hunting behavior of the bat, Pipistrellus kuhfi Hans-Ulrich Schnitzler 1, Elisabeth Kalko 1, Lee Miller 2, and Annemarie Surlykke 2 1 Lehrbereich Zoophysiologie, Universitfit Tfibingen, D-7400 T/ibingen, Federal Republic of Germany 2 Institute of Biology, Odense University, DK-5230 Odense, Denmark Accepted March 12, 1987 Summary. The echolocation and hunting behavior of Pipistrellus kuhli was studied in the field using multi-exposure photography synchronized with high-speed tape recordings. During the search phase, the bats used 8-12 ms signals with sweeps (sweep width 3-6 kHz) and pulse intervals near 100 ms or less often near 200 ms (Figs. I and 2). The bats seemed to have individual terminal fre- quencies that could lie between 35 and 40 kHz. The duty cycle of searching signals was about 8%. The flight speed of hunting bats was between 4.0 and 4.5 m/s. The bats reacted to insect prey at dis- tances of about 70 to 120 cm. Given the flight speed, the detection distance was estimated to about 110 to 160 cm. Following detection the bat went into the approach phase where the FM sweep steepened (to about 60 kHz bandwidth) and the repetition rate increased (to about 30 Hz). The ter- minal phase or 'buzz', which indicates prey cap- ture (or attempted capture), was composed of two sections. The first section contained signals similar to those in the approach phase except that the pulse duration decreased and the repetition rate increased. The second section was characterized by a sharp drop in the terminal frequency (to about 20 kHz) and by very short pulses (0.3 ms) at rates of up to 200 Hz (Figs. 1 and 3). Near the beginning of the buzz the bat prepared for capturing the prey by extending the wings and forming a tail pouch (Fig. 4). A pause of about 100 ms in sound emis- sion after the buzz indicated a successful capture (Fig. 4). Pulse duration is discussed in relation to glint detection and detection distance. It is argued that the minimum detection distance can be esti- mated from the pulse duration as the distance where pulse-echo overlap is avoided. Abbreviations: CF constant frequency, FM frequency modu- lated Introduction The echolocation behavior of bats hunting for in- sects has been described by several authors (for reviews see Novick 1977; Simmons et al. 1979; Schnitzler and Henson 1980; Pye 1980; Neuweiler 1983). All studies indicate that the three behavioral stages: search, approach and terminal phases used by Griffin et al. (1960) to describe the pulse pat- terns of vespertilionids hunting insects can be gen- eralized for all bats. Studies on hunting behavior and capture techniques in bats suggest that the capture techniques described by Webster and Grif- fin (1962) such as mouth, tail membrane, wing scoop and somersault catches are representative of most bats. Most studies describe either echolo- cation behavior or hunting behavior of bats. Grif- fin et al. (1960), Webster (1963), Trappe (1982), Trappe and Schnitzler (1982), Vogler and Neu- weiler (/983) studied both behaviors at the same time using synchronous recordings of the echoloca- tion signals and filming or photographing hunting bats in the laboratory. Corresponding field studies are lacking. The development of a battery operated 6 flash strobe system synchronized with our high speed tape recorder made it possible for us to un- dertake field studies of foraging bats. The equipment is bulky and cannot be moved during a recording session. Therefore we had to find a bat species that reliably hunted in an open area where we had a chance to record the sounds and photograph the bats. Pipistrellus kuhli, one of the four European pipistrelle species, fulfilled all these conditions. In Yugoslavia we found a site where bats hunted for insects near a street light. We could make nearly 500 photographs from passing and hunting bats. The data of ten nights are presented in this paper. The echolocation and hunting behav- ior of this species has not yet been described.