Cross-species effect of separation calls: family dogs’ reactions to pup, baby, kitten and artificial sounds

Abstract

During separation, infants of various species often produce a special call type, the separation cry, which elicits instant response from the caregiver. Ignoring this stimulus might be costly; hence, adults have evolved a sensitivity to infant cries. As the acoustic structure and function of these vocalizations are conserved across mammals, adults might react similarly to heterospecific and conspecific separation calls. The domestic dog, Canis familiaris, is an excellent model to study reactions to heterospecific vocalizations due to their special niche in the human social environment. Through domestication, they have become especially sensitive to human communicative signals, including baby cries. Furthermore, they can share their natural environment with other species such as other pets and livestock, which could also affect their responsiveness towards heterospecific calls. Taking advantage of this potential cross-species sensitivity, we aimed to examine dogs' reactions to infant separation calls of humans and domestic cats, Felis catus, compared to conspecific calls. To explore the effect of novelty and specific acoustic features we also used synthesized cries, which allowed us to look for general rules behind dogs' reactions to heterospecific calls and general acoustic effects functioning across species. After testing 100 dogs with pup cries in a previous study, here we tested another 118 dogs in three groups based on the presented sounds' origin. All stimuli were analysed acoustically; then we tested the effects of the species and acoustic features on the dogs’ behaviours. Dogs reacted to pup and artificial cries the fastest, and baby cries the slowest, while responses to kitten sounds were intermediate. We also found general acoustic effects: tonality-related parameters extensively affected the reactions. Higher noisiness caused faster speaker and owner orientation, but it seems that species-specific cues might overwrite the general acoustic rules that appear across mammal separation calls.