ANA COTTA / WIKIMEDIA COMMONSTiti monkey: calls indicate both the type and location of predatorsANA COTTA / WIKIMEDIA COMMONS
Black-fronted titi monkeys talk to each other while moving through the trees of the Atlantic Forest. Those who lead the way emit squeaks like bird calls that indicate the proper way to go and the presence of danger. Now we know that these warning calls can contain two types of information. “The vocalizations of the titi monkeys indicate the type of predator and its location,” says Cristiane Cäsar, biologist at the Pontificate Catholic University (PUC) in Minas Gerais. For three years, she has been monitoring five groups of titi monkeys in the Caraça mountain range in the Brazilian state of Minas Gerais, using stuffed samples of two predators – the caracara and the oncilla – to study communication among the monkeys. Along the pathways used by the titis, she placed the oncilla on the ground, where it is generally found, or in the canopy, where the monkeys are less used to seeing it. And she did the same with the caracara. From a camouflaged tent, she recorded the calls and saw that the monkeys emitted different sounds, both high-pitched and short, one for the caracara in the canopy and the other for the oncilla on the ground. The calls change when the cat is in the tree and the bird is on the ground. The titis intersperse their vocalizations indicating “bird” with that of the “ground predator” to warn of a caracara on the ground. When the oncilla is in the trees, the call begins with a squeak that indicates a threat from above followed by squeaks that define the predator (Biology Letters, September 2013). “This is the first time this ability is seen in neotropical primates,” she says.
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