The development of social behavior during early ontogeny through play in free-ranging domestic dogs (Canis familiaris) (#212)
Twenty one free-ranging dog puppies belonging to five litters were observed from birth to 13 weeks of age to study how different types of behaviours are developed during early ontogeny through playful interactions. Behavioural data were collected using focal animal sampling. The duration of each observation session was 30 min with a total of 90 min observation per litter per day; and a total of 690 h was devoted to collect data. Mean litter size was 6.12 ranging from 4 to 9 with a male-biased sex ratio of 1.21:1. Eye slits were observed on day 12 (median) of life, and the eyes completely opened on day 17 (median) of life. The puppies were mobile at the age of week 3 when the eyes completely opened. Social investigation was first observed with 3 weeks of age, and then subsequently developed other play behaviors like play-fighting (week 4), play-mounting (week 4), aggressive play (week 5), objects play (week 5) and pseudo-sexual play (week 6). The litters were significantly different from each other in relation to their frequency of playful interactions (F = 12.04; df = 4, 40; P < 0.0001). The rate of play bouts per hour increased with the age of the puppies (r = 0.9871, P = 0.05), but it suddenly decreased in week 10, and continued thereafter (r = -0.9457). Male puppies initiated playful interactions with a greater frequency than did female puppies (t = 2.981, df = 10, P < 0.0138). Except in the case of aggressive play, male puppies initiated play more often with female puppies and vice versa showing the evidence of inter-sexual play in free-ranging dogs. From this study it may be suggested that 3 to 13 weeks of age is the most important developmental periods of puppies life; and one should adopt the puppy between seven and ten weeks of age.