Phonotactic responses of Brown Rats (Rattus norvegicus) to begging calls of Starling nestlings (Sturnus vulgaris)
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| Authors: | Takacs, S; Gries, G |
| Year: | 2021 |
| Journal: | J. Ornithol. 162: 1173-1181 Article Link (DOI) |
| Title: | Phonotactic responses of Brown Rats (Rattus norvegicus) to begging calls of Starling nestlings (Sturnus vulgaris) |
| Abstract: | Foraging behavior of Brown Rats (Rattus norvegicus) is commonly thought to be guided by olfactory cues. Here we tested the hypothesis that foraging Brown Rats eavesdrop on bird vocalizations to locate prey. We recorded calls of nestling Starlings (Sturnus vulgaris) with microphones sensitive in the sonic and ultrasonic range, respectively, and compiled clear begging calls into a single sound file (2-min long) which included the entire recorded sound range (0-100 kHz; Audio File 1). Sound analyses revealed a fundamental two-tone modulated sound centered around 3 kHz, a first and second harmonic at, respectively, 9 and 16 kHz, and bands of ultrasonic frequency components at 20, 25, and 37 kHz. We subjected Audio File 1 to low- and highpass-filtering, thereby producing a sonic-range only file (< 20 kHz; Audio File 2), and an ultrasonic-range only file (20-100 kHz; Audio File 3). In binary-choice large arena bioassays, we then tested the behavioral responses of single Brown Rats to paired trap boxes each fitted with a speaker, one of which emitting a white noise control and the other playing back Audio File 1 (Exp. 1), Audio File 2 (Exp. 2), or Audio File 3. In each of experiments 1-3, female and male rats (i) significantly more often entered first the trap box broadcasting an Audio File, and (ii) spent significantly more time in the arena quadrant with an Audio File trap box. Our data support the conclusion that foraging Brown Rats, as opportunistic omnivores, exploit begging calls of nestling Starlings, and possibly other birds, as cues to obtain a proteinaceous meal. |
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