CAMILLE WARD, ERIKA B. BAUER† & BARBARA B. SMUTS
*Department of Psychology, University of Michigan, Ann Arbor
Department of Animal Programs, Smithsonian National Zoological Park, Washington, D.C.

(Received 30 November 2007; initial acceptance 27 February 2008;
final acceptance 13 May 2008

We videotaped behaviour in four litters of domestic dogs to explore social play and the development of
relationships within litters. We collected data when the puppies were between 3 and 40 weeks of age,
but collection times varied by litter. We divided data analysis into three time periods to coincide approximately with critical periods in the early social development of dogs. Early play-partner preferences were
associated with preferences in later time periods, and the tendency for puppies to prefer specific partners
increased over time. Play did not conform to 50:50 symmetry of roles between partners, which some
researchers claim is necessary to sustain play. In the later juvenile period (time 3), dogs who engaged in
high rates of offense behaviours (e.g. chasing, forcing partners down) also initiated play at higher rates,
implying that winning during play may become more important as puppies mature. Self-handicapping
behaviours were positively associated with play signalling, suggesting that, like play signals, self-handicapping may function to indicate playful intent. In mixed-sex dyads, males initiated play, engaged in offense
behaviours, and self-handicapped more than females. Females were more likely to initiate with females
across all time periods, but males were more likely to initiate with males only in time 3. We discuss results
from mixed- and same-sex interactions with reference to inter- and intrasexual competition. The types of
offense and self-handicapping behaviours displayed were similar across litters, suggesting that the expression of these behaviours may follow a similar ontogeny in puppies in general.