Answers are grounded in this paper and cite their sources.
The variability in the duration and form of the canid play bow was studied in infant coyotes, wolves, wolf-dog hybrids, beagles, and adult free-ranging dogs. Both duration and form showed marked stereotypy. It appears that the role of this context-specific social signal in the communication of play intention has been fostered by selection for "morphological" stereotypy.
No takes yet. Share an insight, caveat, or question.
Marc Bekoff (1977) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: