Frequency alternation and an offbeat rhythm indicate foraging behavior in the echolocating bat, <Emphasis Type="Italic">Saccopteryx bilineata</Emphasis> |
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Authors: | John M Ratcliffe Lasse Jakobsen Elisabeth K V Kalko Annemarie Surlykke |
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Institution: | (1) Institute of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark;(2) Institute of Experimental Ecology, University of Ulm, Albert-Einstein Allee 11, 89069 Ulm, Germany;(3) Smithsonian Tropical Research Institute, P.O. Box 0843-03092, Balboa, Ancon, Republic of Panama |
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Abstract: | The greater sac-winged bat, Saccopteryx bilineata (Emballonuridae), uses two distinct echolocation call sequences: a ‘monotonous’ sequence, where bats emit ~48 kHz calls at
a relatively stable rate, and a frequency-alternating sequence, where bats emit calls at ~45 kHz (low-note call) and ~48 kHz
(high-note call). The frequencies of these low–high-note pairs remain stable within sequences. In Panama, we recorded echolocation
calls from S. bilineata with a multi-microphone array at two sites: one a known roosting site, the other a known foraging site. Our results indicate
that this species (1) only produces monotonous sequences in non-foraging contexts and, at times, directly after emitting a
feeding buzz and (2) produces frequency-alternating sequences when actively foraging. These latter sequences are also characterized
by an unusual, offbeat emission rhythm. We found significant positive relationships between (1) call intensity and call duration
and (2) call intensity and distance from clutter. However, these relationships were weaker than those reported for bats from
other families. We speculate on how call frequency alternation and an offbeat emission rhythm might reflect a novel strategy
for prey detection at the edge of complex habitat in this ancient family of bats. |
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