Other mechanisms may also lead to this acoustical ‘exaggeration’ e.g., male saiga antelopes ( Saiga tatarica) use a specific vocal posture while producing mating calls (Volodin et al., 2009), while elephant seals ( Mirounga leonina) have an elongated nasal region that is able to potentially influence the spacing of formants (Sanvito et al., 2007, Taylor and Reby, 2010).ĭomestic dogs have a rich vocal repertoire (Cohen and Fox, 1976). For example, in male red ( Cervus elaphus) and fallow deer ( Dama dama), the larynx rests in an unusually low position in the neck, and it can be further retracted in the throat during the production of mating calls (Reby et al., 2005). As a result, the vocal signal may not reflect the callers’ real body size in certain situations (Taylor and Reby, 2010). ![]() ![]() ![]() More closely spaced formants reflect to a longer vocal tract, which is related to a larger body size (Taylor and Reby, 2010).ĭespite the association between an acoustical signal and the caller's physical parameters, the strength of this relationship might depend on certain anatomical adaptations, and the caller may be able to modulate the vocal signal depending on the context. It has been shown, that the average spacing between succeeding formants (spectral peeks in the vocal signal), termed ‘formant dispersion’ is directly linked to the vocal tract length, which in turn is in close association with the overall body size and acts as an indexical cue in several mammalian species (e.g., dog ( Canis familiaris): Riede and Fitch, 1999 american bison ( Bison bison): Wyman et al., 2012 koala ( Phascolarctos cinereus): Charlton et al., 2011). Thus, vocalizations have the potential to provide receivers with direct information on the callers phenotype and/or motivational state (Charlton et al., 2010, Fitch and Hauser, 2003). The source-filter theory of vocal production (Fant, 1960) links acoustic features of mammal calls to the anatomy of the vocal apparatus that creates them. As agonistic dog growls were proven to be honest regarding their referential and size-related information content, our results gave evidence that exaggeration may work as play signal in the case of animal vocalizations. These are the first results to show that dogs may communicate an exaggerated body size by the means of their growls during play, which may help in maintaining or enhancing the playful interaction. We found that dogs looked at the matching picture when they heard the food-guarding growl, but they looked at rather the larger than the matching size dog when play growls were played back. ![]() Using the cross-modal matching paradigm, we tested whether dogs prefer to look at the picture of a matching size dog when they are offered two differently sized projected pictures simultaneously with a playback of a playful or a food-guarding growl. Scientists have already collected knowledge about virtual size modification via acoustic signalling in particular animal species during competitive/agonistic interactions, but the same was unknown in playful encounters. Playful encounters include out-of-context and exaggerated behavioural sequences. There is evidence also for different forms of play-maintenance. Nonhuman animals often use specific signals to initiate playful interactions.
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