Monkey Meltdowns: Do Tantrums Influence Maternal Investment in Bearded Capuchin Monkeys?

Tantrums are widely discussed in human development literature and are typically defined as displays of frustration or anger. In behavioral ecology, they are hypothesized to function as a strategy for securing greater maternal investment. Infant primates often exhibit tantrums when their attempts to obtain maternal care are rejected. We investigated whether these displays influence maternal investment in a wild population of capuchin monkeys (Sapajus libidinosus) at Fazenda Boa Vista, Brazil. We analyzed 213 h of footage of 12 infants filmed over their first 18 months of life using focal animal sampling and identified 550 infant solicitation events for nursing and transportation. Maternal rejection was rare (N = 47) but increased significantly with age. Infants displayed tantrums after most rejections (N = 31), but their occurrence did not vary significantly with age and had no significant effect on the likelihood of obtaining maternal care. Infant solicitations declined significantly with age, suggesting that maternal investment decreases as infants' behavior changes. Our findings suggest that tantrums may reflect the challenges infants face during the transition to independence associated with weaning rather than an effective strategy for securing additional maternal care. By not reinforcing tantrums, mothers may facilitate infants' gradual adjustment and shift toward greater independence.