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Megan M. Joyce, Brittany M. Talarico, Kelsey J. Wilson, and Sarah E. Turner
Early ontogenic development and maternal care of disabled infants in a free-ranging group of Japanese macaques (Macaca fuscata)
Physical impairments, such as congenital limb malformations (CLMs) or hydrocephalus, are relatively rare among human and nonhuman primates. Here, we aim to observe how physical impairments influence the growth, development, and socialization of infants belonging to a group of free-ranging Japanese macaques at the Awajishima Monkey Center, Awaji Island, Japan. We recorded 200 minutes (or 20 x 10-minutes) of focal samples over a two-month period for each of the 3 physically impaired infants (two with CLMs and one with hydrocephalus) born in the group that year, and for 3 control infants who were pair-matched based on age and the mother’s rank. Results from our analysis suggest that: (1) mothers of disabled infants provide more support behaviours (e.g., during nursing and when carrying during travel) than mothers of non-disabled infants; (2) disabled infants spend more time in rest (or inactive) behaviours compared to the non-disabled controls; and (3) even in early stages of development, behavioural flexibility emerges (e.g., vertical climbing stratum using the crooks of the elbow versus the hands). Higher levels of maternal investment (e.g., support behaviours) facilitates long-term survival of physically impaired infants in this population. Further, this research contributes to our understanding of primate behavioural flexibility and when it emerges during early development stages.
