Monkey Methods

Arguably the most widely known fact about capuchin monkey behaviour is that they use tools. Capuchins have been seen in both captivity and the wild using a wide variety of tools and it allows them to access food sources that they wouldn’t be able to normally exploit. There are lots of examples of different capuchin species (both Cebus and Sapajus) using various tools. Blonde and black-capped capuchins (Sapajus flavius and S. libidinosus) living in the Brazilian Caatinga use hammer stones and anvils to smash hard shelled nuts (Ferreira et al. 2009). An adult male white-faced capuchin (Cebus capucinus) in Costa Rica was observed using a branch as a club to kill a venomous snake (Bothrops asper) (Boinski 1988).

Credit: Barth W. Wright/Kansas City University

Profitt et al (2016) reported in Nature that black-capped capuchins in Brazil smash rocks, producing flakes and cores that have the same characteristics of the tools produced by our own ancestors - a huge discovery. Check out a great video and article on this behaviour here:

http://www.nature.com/news/monkey-tools-raise-questions-over-human-archaeological-record-1.20816?WT.mc_id=FBK_NatureNews

I haven’t yet seen full tool use in my capuchin groups in Laguna Blanca but we have seen complex object manipulation. The capuchins use “First Order” manipulation techniques. This means that they combine an object with a hard surface or another stationary object. In Laguna Blanca the capuchins smash the hard-shelled fruits of the Ka’I Ka’gua tree (Cariniana estrellensis) to loosen and access the seed inside.  The capuchins use two different techniques to open the fruits involving hammering the fruit using one hand or using two hands and the entire body weight to hit the fruit on the branch. The younger monkeys are not very good at opening the seeds and their attempts often ending up with the fruit flying unopened out of the tree as they rolled it along the branch and then let it go!

Adult capuchin selecting a fruit to hammer.

This information is the first description of this behaviour in wild Paraguayan capuchins and a full description of the techniques has recently been accepted for publication. Watch this space for information on when the article will be available!

This fascinating behaviour is something that we are keeping a close eye out for in our studies of the capuchins in Laguna Blanca. In the future I hope to be able to investigate whether this behaviour is a socially learned, like nut smashing in other capuchin species (Fragaszy et al. 2013) and how much variation there is in smashing technique between individuals of different age and sex classes.