Social dynamics and individual plasticity of infant care behavior in cooperatively breeding cotton‐top tamarins

Abstract

Individual variation in infant caretaking behavior is prevalent among marmoset and tamarin monkeys. Although most group members participate in infant care, the timing and amount provided differs greatly. In this study, we quantified general trends in infant carrying behavior by using a longitudinal database that included 11 years of instantaneous scan observations following 80 births of cotton-top tamarins. Using detailed focal observations on a subset of the same families (10 births) we identified influences that affected expression of infant care at the group and individual levels. Fathers were the primary carriers and paternal carry time gradually decreased with increasing infant age. Paternal carry time also decreased significantly with an increasing number of older sibling helpers. Most fathers began to carry on the first day postpartum. However, we report circumstances in which fathers delayed carrying until almost a month postpartum. Fathers retrieved infants the most, although adult brothers' rates of retrievals peaked and surpassed fathers' rates during week 4 postpartum. Fathers delayed rejection of infants until week 4, whereas mothers rejected infants immediately and throughout the eight weeks. Nonetheless, infants climbed onto their mothers more than onto any other family member. Mothers showed a high initial investment in carrying during the first two weeks, decreasing quickly thereafter. Maternal contributions to infant carrying remained low and relatively consistent regardless of group size. However, mothers dramatically increased their infant carrying behavior in families in which fathers were absent. Older siblings cared for infants more than did younger siblings, and brothers retrieved and carried infants more than did sisters. Individual expression of infant care changed to accommodate infant needs and changed according to varying social dynamics and circumstances across litters.

Oxytocin is associated with infant-care behavior and motivation in cooperatively breeding marmoset monkeys

“…Nevertheless, caretakers also compete over access to infants (Mills et al, 2004;Yamamoto and Box, 1997;Zahed et al, 2010), and particularly female helpers are not always tolerated by other group members to handle and carry infants as much as they attempt to (Albuquerque, 1999;Price, 1991). Hence, individual infant-carrying contributions may not necessarily correspond to intrinsic motivational levels, especially if more care-takers than infants are available.…”

The Effect of Infant Body Mass on Carrier Travel Speed in Cotton-top Tamarins (Saguinus oedipus)

“…If fatigue plays a role in tamarin speed, we would expect helpers from smaller groups to move more slowly, especially when carrying two infants. Unfortunately, the majority of our groups were large, with more than three helpers (Zahed et al 2010), and only one father was the sole helper in a twin birth, which prevented us from exploring this effect.…”

“…Similarly, the occasional birth of twins involves greater than normal rates of allomothering in noncooperative breeding species, such as spider monkeys (Ateles belzebuth: Link et al 2006), Japanese monkeys (Macaca fuscata: Nakamichi 1983), or banded langurs (Presbytis melalophos: Bennett 1988). In small groups of cotton-top tamarins, helpers carry infants more than in large groups (Washabaugh et al 2002;Zahed et al 2010), and they also assume greater costs (Achenbach and Snowdon 2002). If fatigue plays a role in tamarin speed, we would expect helpers from smaller groups to move more slowly, especially when carrying two infants.…”

Social Dynamics and Cooperation: The Case of Nonhuman Primates and Its Implications for Human Behavior

“…In cottontop tamarins specifically, the interbirth interval for the breeding pair is six months, and dams give birth to twins that can weigh up to 20% of the mothers' body weight collectively. The twins require continuous carrying for the first month of life and continue to be carried for up to 12 weeks [75]. Furthermore, the biological mother is often pregnant with the next litter and nursing the previous litter simultaneously.…”