Titi monkey call sequences vary with predator location and type

Abstract

Animal alarm calls can encode information about a predator's category, size, distance or threat level. In non-human primates, alarm calls typically refer to broad classes of disturbances, in some instances to specific predators. Here, we present the results of a field experiment with a New World primate, the black-fronted titi monkey (Callicebus nigrifrons), designed to explore the information conveyed by their alarm call system. Adults produced sequences consisting of two main alarm call types that conveyed, in different parts of the utterance, information about a predator's type and location. In particular, sequence compositions differed depending on whether the predator was a mammalian carnivore or a raptor, and whether it was detected in a tree or on the ground. This is the first demonstration of a sequence-based alarm call system in a non-human animal that has the capacity to encode both location and type of predatory threat.

Keywords: New World monkeys; alarm calls; predator models; sequences.

Figure 1.

Sequential analyses of the first 30 calls produced by black-fronted titi monkeys after encountering two species of predators in the canopy or on the ground.

Figure 2.

Histograms indicating the (a) median duration of calling behaviour when encountering two species of predators in the canopy or on the ground (b) median number of calls produced per individual. Box plots represent medians and upper and lower quartiles. Outliers are marked with circles.