Fruit Availability and Maternal Energy Expenditure Associated With Infant Independence in an Arboreal Primate (Colobus angolensis ruwenzorii)

Abstract

A range of ecological and social factors have been shown to affect early-life behaviour in mammals. Primate infants are altricial and thus unable to move independently at birth. As a result, infants in some species are continuously held or carried (handled) by their mother or another caregiver (allomother). Variation in the amount of time infants move independently can provide insight into the costs and benefits associated with this developmental milestone. In this study, we sought to investigate what environmental conditions are associated with independence in an arboreal primate, the Rwenzori Angolan colobus (Colobus angolensis ruwenzorii). We followed 29 infants from birth until 4 months, collecting data on whether the infant was handled or independent. We report the age-sex make up of infant handlers and show that fruit availability was positively associated with infant independence, and maternal movement frequency was negatively associated with infant independence. We suggest that greater maternal energy balance during early infancy allows mothers to divert more energy to infants, promoting their independent movement. Further research should assess the maternal physiology underlying these trends and whether earlier independent movement has long-term fitness effects.