Suffixation influences receivers' behaviour in non-human primates.

Area of Science:

• Primate communication
• Bioacoustics
• Animal behavior

Background:

• Non-human primates have limited vocal control compared to humans.
• Some primates use call combinations to enhance communication.
• Campbell's monkeys (Cercopithecus campbelli) use 'Krak' for leopards and 'Krak-oo' for general danger.

Purpose of the Study:

• To investigate if Diana monkeys (Cercopithecus diana diana) distinguish between suffixed and unsuffixed 'Krak' calls.
• To determine the functional significance of suffixation in primate vocalizations.
• To assess the role of call modifications in conveying specific threat information.

Main Methods:

• Playback experiment using naturally and artificially modified 'Krak' calls.
• Broadcasted calls to 42 wild groups of Diana monkeys.
• Analyzed vocal responses of male and female Diana monkeys.

Main Results:

• Diana monkeys showed significantly stronger vocal responses to unsuffixed ('leopard') calls than suffixed ('unspecific danger') calls.
• The presence or absence of the suffix was the primary determinant of response.
• Acoustic structure of the call stem had a secondary effect on responses.

Conclusions:

• Suffixation in primate vocalizations is an evolved communication strategy.
• This strategy is particularly important in contexts requiring adaptive responses to threats.
• Primate vocal communication can convey specific information despite limited vocal flexibility.