Development of Echolocation Calls in the Mustached Bat, Pteronotus parnellii

• Published in: Journal of neurophysiology 2003-10, Vol.90 (4), p.2274-2290
• Main Authors: Vater, M, Kossl, M, Foeller, E, Coro, F, Mora, E, Russell, I. J
• Format: Article
• Language: English
• Subjects: Acoustic Stimulation - methods; Age Factors; Animals; Animals, Newborn; Chiroptera - growth & development; Echolocation - physiology; Pteronotus parnellii
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00101.2003

1 Institute of Biochemistry and Biology, University of Potsdam, 14471 Potsdam 2 Zoological Institute, University of Frankfurt, 60323 Frankfurt am Main, Germany 3 Department of Animal Physiology, University of Habana, Calle 25 #455, Vedado, La Habana, Cuba 4 School of Biology, University of Sussex, Falmer, Brighton BN19QG, United Kingdom Submitted 3 February 2003; accepted in final form 18 June 2003 Adult mustached bats employ Doppler-sensitive sonar to hunt fluttering prey insects in acoustically cluttered habitats. The echolocation call consists of 4–5 harmonics, each composed of a long constant frequency (CF) component flanked by brief frequency modulations (FM). The 2nd harmonic CF component (CF 2 ) at 61 kHz is the most intense, and analyzed by an exceptionally sharply tuned auditory system. The maturation of echolocation calls and the development of Doppler-shift compensation was studied in Cuba where large maternity colonies are found in hot caves. In the 1st postnatal week, infant bats did not echolocate spontaneously but could be induced to vocalize CF-FM signals by passive body motion. The CF 2 frequency emitted by the smallest specimens was at 48 kHz (i.e., 0.4 octaves lower than the adult signal). CF-FM signals were spontaneously produced in the 2nd postnatal week at a CF 2 frequency of 52 kHz. The CF 2 frequencies of induced and spontaneous calls shifted upward to reach a value of 60.5 kHz in the 5th postnatal week. Standard deviations of CF 2 frequency were large (up to ±1.5 kHz) in the youngest bats and dropped to values of ±250 Hz at the end of the 3rd postnatal week. Some individuals in the 4th and 5th postnatal weeks emitted with adultlike frequency precision of about ±100 Hz. In the youngest bats, the 1st harmonic CF component (CF 1 ) was up to 22 dB stronger than CF 2 . Adultlike relative levels of CF 1 (–28 dB relative to CF 2 ) were reached in the 5th postnatal week. In spontaneously emitted CF-FM calls, the duration of the CF 2 component gradually increased with age from 5 ms to maximum values of 18 ms. Durations of the CF 2 component in induced calls averaged 7 ± 2.6 ms in the 1st postnatal week and 8.2 ± 1.5 ms in the 5th postnatal week. There were no age-related changes in duration of the terminal FM sweep (3 ± 0.4 ms) in both induced and spontaneous calls. The magnitude of the terminal FM sweep in spontaneous calls was not correlated with age (mean 13.5 ± 2 kHz). Values for induced calls slightly increased with age from 11 ± 2 to