Task Specialization in Infant Care in Wild Coppery Titi Monkeys (Plecturocebus cupreus)

Cooperative breeding is hypothesized to be central to human life history since it reduces the energetic investment from the mother to her offspring by distributing the energetic cost across multiple caregivers. Biparental care offers a simplified system to examine this hypothesis since maternal care is only modified by the care of one other individual. The Task Specialization Hypothesis posits that, in biparental systems, each parent performs unique tasks with minimal overlap, resulting in the necessity of care from both parents for successful reproduction. While biparental care is rare in mammals, it occurs in some primates; infants are actively cared for by both parents in coppery titi monkeys (Plecturocebus cupreus). Questions remain regarding how mothers and fathers contribute, and to what extent their caring tasks are specialized.

For 13 months, we observed 1300 h of infant care provided by 10 wild coppery titi monkey pairs at Estación Biológica Quebrada Blanco, Peru.

Fathers carried infants 65% of the time while females only carried them 14%. Infants attempted to receive food more often from fathers than mothers (daily rate mean difference = -4.7 attempts) and were more successful at doing so (success rate mean difference = -0.4). Fathers also groomed and played with infants more than mothers did.

Fathers are consistent caregivers to infants and contribute substantially to all caring tasks other than nursing. Our findings show both quantitative and qualitative sex differences in infant care, supporting the Task Specialization Hypothesis.