title: Echolocation in the bat, Rhinolophus capensis: the influence of clutter, conspecifics and prey on call design and intensity.
abstract: Echolocating bats are exposed not only to the echoes of their own calls, but often the signals of conspecifics and other bats. For species emitting short, frequency modulated signals e.g. vespertilionoids, adjustments in both the frequency and time domain have been observed in such situations. However, bats using long duration, constant frequency calls may confront special challenges, since these bats should be less able to avoid temporal and frequency overlap. Here we investigated echolocation call design in the highduty cycle bat, Rhinolophus capensis, as bats flew with either a conspecific or heterospecific in a large outdoor flight-room. We compared these recordings to those made of bats flying alone in the same flight-room, and in a smaller flight room, alone, and hunting tethered moths. We found no differences in duty cycle or peak frequency of the calls of R. capensis across conditions. However, in the presence of a conspecific or the vespertilionoid, Miniopterus natalensis, R. capensis produced longer frequency-modulated downward sweeps at the terminus of their calls with lower minimum frequencies than when flying alone. In the presence of the larger high-duty cycle bat, R. clivosus, R. capensis produced shorter calls than when flying alone or with a conspecific. These changes are similar to those of vespertilionoids when flying from open to more cluttered environments. They are not similar to those differences observed in vespertilionoids when flying with other bats. Also unlike vespertilinoids, R. capensis used calls 15 dB less intense in conspecific pairs than when alone.
authors.affiliation: Sound and Behaviour Group, Department of Biology, University of Southern Denmark, Campusvej 55, DK5230 Odense M, Denmark.
authors.forename: Kayleigh
authors.initials: K
authors.lastname: Fawcett
authors.affiliation: Department of Biological Sciences, University of Cape Town, 7701 Rondebosch, South Africa.
authors.forename: David S
authors.initials: DS
authors.lastname: Jacobs
authors.affiliation: Sound and Behaviour Group, Department of Biology, University of Southern Denmark, Campusvej 55, DK5230 Odense M, Denmark.
authors.forename: Annemarie
authors.initials: A
authors.lastname: Surlykke
authors.affiliation: Sound and Behaviour Group, Department of Biology, University of Southern Denmark, Campusvej 55, DK5230 Odense M, Denmark Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, ON M5S 3B2, Canada Department of Biology, University of Toronto Mississauga, 3359 Mississauga Road, Mississauga, ON L5L 1C6, Canada j.ratcliffe@utoronto.ca.
authors.forename: John M
authors.initials: JM
authors.lastname: Ratcliffe
keywords: Acoustic interference; Bats; High-duty cycle echolocation; Intensity; Jamming