Do dogs respond to play signals given by humans?

Play signals are known to function in the solicitation and maintenance of i ntraspecific play, but their role in interspecific play is relatively unstu died. We carried out two studies to examine interspecific signalling when h umans play with domestic dogs, Cais familiaris. In the first, we recorded d og-owner play sessions on video to identify actions used by 21 dog owners t o initiate play with their dogs. Thirty-five actions were each used by thre e or more owners. These;included postures, vocalizations and physical conta ct with the dog. The actions varied greatly in their apparent success at in stigating play which was, surprisingly, unrelated to the frequency with whi ch they were used. We then did an experiment to determine the effect of com posites of commonly used signals upon the behaviour of 20 Labrador retrieve rs. The performance of both 'Bow' and 'Lunge' by a human altered the subseq uent behaviour of the dogs. Both signals caused increases in play, and Lung e produced significant increases in play bout frequency and mean bout durat ion. The efficiency of both these postural signals was enhanced when they w ere accompanied by play vocalizations. Thus, specific actions used by human s do communicate a playful context to dogs and san be described as interspe cific play signals. (C) 2001 The Association for the Study of Animal Behavi our.