Green monkeys' repertoires maintain consistency on Caribbean islands despite centuries of geographic isolation

Green monkeys (Chlorocebus sabaeus) were introduced to the Caribbean in the 17th century. Since then, they have established isolated populations on the islands of Barbados, St. Kitts and St. Martin. This geographic distribution provides a unique opportunity to assess communication differences that may have arisen in these populations over this period of geographic isolation from the native West African population. Using an established vocal repertoire from monkeys living in Barbados, we investigated how call types may have diverged across these three islands. We collected vocal data from St. Kitts and St. Martin monkey populations and used Raven Pro to isolate vocalizations and collect acoustic measurements. We then statistically compared each call type to the same call type made in the other populations to identify areas of change. We found that the majority of call types did not drastically differ in acoustic parameters across islands, suggesting that vocal repertoires are largely conserved within species despite long periods of separation. However, some call types did exhibit differences in both acoustic parameters and degree of usage. For example, populations that experienced higher levels of human food provisioning made call types unique to these events. Further, the rates of call type usage varied across islands, illustrating an underlying dynamic of change in which monkey populations are shifting their vocal repertoires in response to variation within their environments. These findings emphasize the need for further investigation into how repertoires are impacted by other environmental, social, and anthropogenic factors.