Unusual echolocation behavior in a small molossid bat, Molossops temminckii, that forages near background clutter

Original Paper

Abstract

When searching for flying insects, Molossops temminckii uses unusual echolocation calls characterized by upward modulation of frequency vs time (UFM). Call frequency increases asymptotically in the relatively long (∼8 ms) pulses from a starting frequency of ∼40 kHz to a long narrowband tail at ∼50 kHz. When approaching a prey, the bat progressively increases the duration of calls and intersperses in the sequence broadband downwardly frequency-modulated signals with a terminal frequency of about 53 kHz, which totally replaces the UFM signals at the end of the approach phase. The sequence progresses to a capture buzz resembling those from other molossid and vespertilionid bats. The M. temminckii wing morphology is characterized by an average aspect ratio and a high wing loading, suggesting that it is more maneuverable than the typical Molossidae but less than typical Vespertilionidae. M. temminckii regularly forages near clutter, where it needs to pay attention to the background and might face forward and backward masking of signals. We hypothesize that the UFM echolocation signals of M. temminckii represent an adaptation to foraging near background clutter in a not very maneuverable bat needing a broad attention window. The broadband component of the signal might serve for the perception of the background and the narrowband tail for detection and perhaps classification of prey. Bats may solve the signal masking problems by separating emission and echoes in the frequency domain. The echolocation behavior of M. temminckii may shed light on the evolution of the narrowband frequency analysis echolocation systems adopted by some bats foraging within clutter.

Keywords

Echolocation Evolution Foraging behavior Molossops temminckii Narrowband signals 

Notes

Acknowledgment

We are most grateful to Carlos Ruiz Benavides, Ariany García, and Esquisa Omaña for their help during field work in Venezuela. The staff at the El Frío Biological Station, particularly Rafael Antelo, Juanma and Julio, provided invaluable logistic support for the field work. The Maldonado family, owner of the ranch “Hato El Frío,” has enforced a reconciled management of the land. This allows the conservation of the natural habitats and the persistence of the rich wildlife that we have been studying. Funding for travel and fieldwork in 2006 was provided by grant no. 39709 from the Mexican National Council for Science and Technology (CONACyT). The research reported here complied with the current laws of the Republic of Venezuela. Michael Smotherman, Winston C. Lancaster, and two anonymous referees made fundamental critical comments on earlier versions of this paper. Charles M. Francis and Leonel Torres helped us in revising the language.

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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.Instituto de Ecología, A. C.XalapaMéxico
  2. 2.Estación Biológica de Doñana (CSIC)SevillaSpain

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