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Black-fronted Titi - Callicebus nigrifrons
Black-fronted Titi - Callicebus nigrifrons

[Image: 346px-Callicebus_nigrifrons_Minas_Gerais.jpg]

Scientific classification
Kingdom:  Animalia
Phylum:  Chordata
Class:  Mammalia
Order:  Primates
Suborder:  Haplorhini
Infraorder:  Simiiformes
Family:  Pitheciidae
Genus:  Callicebus
Species:  Callicebus nigrifrons (Spix, 1823)

The black-fronted titi (Callicebus nigrifrons) is a species of titi, a type of New World monkey, endemic to Brazil.

[Image: Black-fronted_Titi_area.png]

Black-fronted titi range

Titi monkeys use probabilistic predator calls to alert others in their group

by Bob Yirka ,

[Image: 5cdd38f9418f5.jpg]
Vigilant male titi, standing against a tree. Credit: Geoffrey Mesbahi

A team of researchers with the University of Neuchâtel in Switzerland and the University of St Andrews in the U.K., has found evidence of titi monkeys using probabilistic predator calls to alert others in their group to the presence of different kinds of danger. In their paper published in the journal Science Advances, the group describes their study of several groups of titi monkeys in the wild and what they found.
Titi monkeys are small, social monkeys native to South America. They survive mainly by eating fruit, but also consume other vegetation and even small animals occasionally. They also serve as food for a wide range of predators, which has led to the evolution of warning systems. In this new effort, the researchers focused on the black-fronted titi monkeys living in Brazil. Prior studies have shown that their warning system has evolved to the point that individuals can tell others if they have spotted a flying predator (by giving an A call) or a ground predator (by giving a B call). Interestingly, prior research has also shown that they can mix their calls if needed, for instance, if a raptor lands on the ground, or a terrestrial predator climbs into the trees. In this new effort, the researchers have found that the warning calls of the titi monkeys are even more complex than previously thought.
To learn more about the warning calls of the titi monkeys, the researchers ventured into their natural forest habitat and observed six families of them as they responded to decoy threats—stuffed predators the researchers placed in watchable locations. They not only recorded the calls the monkeys made, but also noted where they were looking when they made them and when the others listened to them.
The researchers found that warning messages were encoded with information based on the proportion of call types. They suggest this indicates that probabilistic meaning was involved in the calls, which allowed the monkeys to add more information for others who were listening. The researchers suggest their findings could lead to better understanding whether human speech evolved from similar types of communications.

Journal Reference:
Mélissa Berthet et al. Titi monkeys combine alarm calls to create probabilistic meaning, Science Advances (2019). DOI: 10.1126/sciadv.aav3991

Previous work suggested that titi monkeys Callicebus nigrifrons combine two alarm calls, the A- and B-calls, to communicate about predator type and location. To explore how listeners process these sequences, we recorded alarm call sequences of six free-ranging groups exposed to terrestrial and aerial predator models, placed on the ground or in the canopy, and used multimodel inference to assess the information encoded in the sequences. We then carried out playback experiments to identify the features used by listeners to react to the available information. Results indicated that information about predator type and location were encoded by the proportion of B-call pairs relative to all call pairs of the sequence (i.e., proportion of BB-grams). The results suggest that the meaning of the sequence is not conveyed in a categorical but probabilistic manner. We discuss the implications of these findings for current theories of animal communication and language evolution.
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