Monkey's Alarm Calls Reveal Predator's Who and Where

Black-fronted titi monkeys mix and match their calls to detail and expose threats

By Ed Yong and Nature magazine

Listen very carefully in the rainforests of Brazil and you might hear a series of quiet, high-pitched squeaks. These are the alarm calls of the black-fronted titi (Callicebus nigrifrons), a monkey with a rusty-brown tail that lives in small family units. The cries are loaded with information.

Cristiane Cäsar, a biologist at the University of St Andrews, UK, and her colleagues report that the titis mix and match two distinct calls to tell each other about the type of predator that endangers them, as well as the location of the threat. Her results are published in Biology Letters.

Cäsar's team worked with five groups of titis that live in a private nature reserve in the Minas Gerais region of Brazil. When the researchers placed a stuffed caracara — a bird of prey — in the treetops, the titis gave out A-calls, which have a rising pitch. When the animals saw a ground-based threat — represented by an oncilla, a small spotted cat — they produced B-calls, sounds with a falling pitch.

However, when the team moved the predator models around, the monkeys tweaked their calls. If the caracara was on the ground, the monkeys started with at least four A-calls before adding B-calls into the mix. If the oncilla was in a tree, the monkeys made a single introductory A-call before switching to B-calls.