How Do Monkeys Communicate?

Monkeys communicate using nearly all their senses: hearing, sight, touch, and smell. They  produce over 26 different noises, or calls, to communicate their emotions, convey information about the outside world, and negotiate interactions with other monkeys. All monkeys of this species seem to make the same noises, so in that sense they are different from humans, who are quite flexible with regard to what sounds they produce as part of their language. Capuchins show a little bit of flexibility regarding the contexts in which they use their sounds, but not much.  In contrast with their fairly rigid vocal communication, they are more creative in their use of gesture and touch to communicate.  Here are a few examples of monkey calls, and what they are used for [click the links to see video and audio of some of these calls made by Keith Heyward!]:

food  calls: these are used to announce discoveries of food, and to claim possession of these foods. Monkeys who have announced ownership are less likely to have their food stolen, though announcing food makes it more likely that other monkeys will come forage near them.

threats: monkeys often announce that they are angry at other monkeys.

trills: monkeys use trills to announce that they are coming over to do something friendly to another monkey.

bursts: these are used to announce that a monkey is moving in a particular direction.

alarm calls: monkeys have several alarm calls, differing very subtly in the way they sound, which announce the presence of particular predators. There are separate alarm calls for humans, birds, dangerous reptiles (boas, rattlesnakes and caiman), scary monkeys from other groups, and dangerous birds.  

screams: these are used to announce that they are upset at someone, and perhaps to call for help from friends and allies.

lost calls and coos: lost calls are very loud calls used to announce that a monkey is separated from its group, or to search for a missing group member.  Coos are made by babies and their mothers in an attempt to reunite with one another.

gargles: We are still investigating this call, but we think that this annoying sound is produced by immature monkeys and females to adult males to gauge whether the male likes them or not.  If he is tolerant of these irritating sounds, it means he likes them, but if he swats them away, it means he doesn’t have a good relationship with them. They are tests of social bonds.

         Capuchins move their bodies in ways that convey not only their attitude, but also their social allegiances. All white-faced capuchins have a rich repertoire of signals to show who their enemies are and who their allies are.  For example, two monkeys may stack on top of each other, bouncing and making threatening faces (with teeth showing), to show that they are united against an enemy monkey.  We call this a coalition.  One monkey may also jerk its head back and forth between an enemy and someone it wants support from, to initiate a coalition; this is called a headflag.  There are also more flexible, idiosyncratic signals.  See for example the section about bond testing, in which a pair of monkeys may develop their own special ritual for demonstrating the strength of its social bond.

         Capuchin monkeys have a much better sense of smell than we do. They leave chemical messages for one another, by spreading urine on their hands, feet and branches, and by rubbing their faces on branches.  They are very excited when they find these chemical messages, and compete with one another for access to this information (e.g. pushing away competitors who want to sniff the same urine), but we are not sure what information they get from them.