Intergroup loud calls, range size, and spacing in Callicebus torquatus

Area of Science:

• Primate behavior
• Bioacoustics
• Animal communication

Background:

• Primate vocalizations play a crucial role in territorial defense and spacing.
• Different species exhibit varied responses to auditory stimuli, reflecting ecological pressures.
• Previous studies on Callicebus moloch suggest vocalizations reinforce territorial boundaries.

Purpose of the Study:

• To investigate the response of free-ranging Callicebus torquatus to recorded intergroup calls.
• To compare the vocal and spatial responses of Callicebus torquatus with Callicebus moloch.
• To understand how range size influences intergroup spacing mechanisms in titi monkeys.

Main Methods:

• Playback experiments using recordings of intergroup calls.
• Observation of free-ranging Callicebus torquatus groups.
• Analysis of behavioral responses, including flight and vocalizations.

Main Results:

• Callicebus torquatus groups fled from recordings of solo adult male calls.
• Groups remained in place and vocalized in response to recordings of duetting adult male and female calls.
• These responses contrast with previously observed behaviors in Callicebus moloch.

Conclusions:

• The response to intergroup calls varies between Callicebus torquatus and Callicebus moloch.
• Range size appears to influence the mechanisms regulating spacing between titi monkey groups.
• In Callicebus torquatus, vocalizations maintain spacing, unlike in Callicebus moloch where they define boundaries.