Tufted capuchin monkeys (Sapajus sp) learning how to crack nuts: Does variability decline throughout development?

• While cracking nuts with tools, inept movements were more frequent in juveniles, which also showed an improvement on efficient striking.
• The most effective behavioral sequence for cracking (take nut, place nut on the anvil, take hammer, strike the nut with the hammer) was more frequently used by the most experienced monkeys, which also used non-optimal sequences.
• Variability in behavior sequences and actions may allow adaptive changes to behavior under changing environmental conditions.

We investigated the process of nut-cracking acquisition in a semi-free population of tufted capuchin monkeys (Sapajus sp) in São Paulo, Brazil. We analyzed the cracking episodes from monkeys of different ages and found that variability of actions related to cracking declined. Inept movements were more frequent in juveniles, which also showed an improvement on efficient striking. The most effective behavioral sequence for cracking was more frequently used by the most experienced monkeys, which also used non-optimal sequences. Variability in behavior sequences and actions may allow adaptive changes to behavior under changing environmental conditions.