Early development of object manipulation in capuchin monkeys: A naturalistic approach

How human and non-human primates develop their object manipulation skills has been considered an important aspect for understanding the evolution of motor and cognitive abilities in the primate order. Here, we aimed to describe the development of object manipulation from birth to 6 months in robust capuchin monkeys, platyrrhine primates well known for their highly manipulative skills, which partly resemble those observed in catarrhines. To our knowledge, this is the first longitudinal study to investigate the developmental trajectory of object manipulation in capuchin monkeys with a naturalistic approach. For this purpose, eight infants from a wild population of bearded capuchin monkeys were studied in the North-East of Brazil. Data were coded from focal-day recordings of these infants. Our results highlighted the speed and trajectory of change in the development of manipulative action over the first 6 months. In the early stages of development, infants use gentle skills to hold and touch objects. Later, with the acquisition of dexterity and postural control, they begin to exhibit behaviors requiring more complex motor patterns and/or combinatorial actions, such as rubbing and hitting objects. Additionally, we found that the target of manipulation shifted over time, with food interactions gaining prominence. Part of our data parallels those from captive-born individuals, whereas some findings suggest that certain manipulative skills might emerge later in wild capuchins.