Abstract
In a two-alternative forced-choice procedure lesser spear-nosed bats, Phyllostomus discolor, had to discriminate between a pure tone stimulus and a sinusoidally frequency-modulated signal generated at the same carrier frequency as the tone. Modulation depths of the SFM stimuli were reduced until the animals' performance dropped below the 75%-correct level which was used to determine difference limens for detection of frequency modulation (FMDL). The dependence of FMDLs on modulation and carrier frequency was systematically investigated. For a carrier frequency of 18.5 kHz, average FMDLs increased from 95 Hz at a modulation frequency of 10 Hz to 820 Hz at a modulation frequency of 2000 Hz which corresponds to Weber ratios (2Δf/f) of 0.005 and 0.044 respectively. Further, difference limens were found to increase linearly in proportion to carrier frequency throughout a major part (9–74 kHz) of the species' hearing range. In comparison to other mammals, P. discolor has a pronounced capability for frequency discrimination which might be related to the extensive use of individually distinct frequency-modulated communication calls and audio-vocal learning.
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Abbreviations
- FM :
-
frequency modulation
- SFM :
-
sinusoidal frequency modulation
- FMDL :
-
frequency modulation difference limen
- CF :
-
constant frequency
- DLF :
-
difference limen for frequency
- VCO :
-
voltage-controlled oscillator
- SPL :
-
sound pressure level
- WR :
-
Weber ratio
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Esser, K.H., Kiefer, R. Detection of frequency modulation in the FM-bat Phyllostomus discolor . J Comp Physiol A 178, 787–796 (1996). https://doi.org/10.1007/BF00225827
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DOI: https://doi.org/10.1007/BF00225827