Humans have a unique ability to learn and modify language throughout their lives. Primate vocalisations appear fixed and innate in comparison, which creates an evolutionary puzzle. However, primates do show evidence of developmental plasticity within their use of calls and the contexts in which they vocalise, suggesting a potential evolutionary connection to the flexibility of language. To better understand these possible connections, I investigated a capuchin call, the twitter, which is a call that appears to show developmental changes. I collected observational focal data and acoustic data on wild white-faced capuchin monkeys in Costa Rica. I examined which behavioural states and specific behaviours were associated with twitters, and whether this showed differences across age groups. I also examined the acoustic structure of twitter calls, looking at whether there were changes across in the acoustic parameters of the call. I found evidence of age-related differences in capuchin twitter calls, which suggests more flexibility in vocal ontogeny and the usage of calls than previously assumed. There appear to be interesting acoustic shifts as well, which suggest greater flexibility in primate vocal development. This call appears to broaden to a whole new context later in life, which is beyond what has been seen before.