Female Putty-Nosed Monkeys Recruit Males to Defend Against Predators

Researchers from the Wildlife Conservation Society Congo Program and the Noubale-Ndoki Foundation found evidence that Cercopithecus nictitans or female putty-nosed monkeys used males of the same species as 'hired guns' to defend them from predators like leopards.

Putty-Nosed Monkeys Symbiotic Relationship

A study published in the journal Royal Society Open Science entitled "Female putty-nosed monkeys (Cercopithecus nictitans) vocally recruit males for predator defense," illustrates how female monkeys use alarms to recruit males of the species for predatory defense.

Researchers observed 19 different groups of wild putty-nosed monkeys in Mbeli Bai within the forests of Nouabale-Ndoki National Park, Congo.

Results showed that the general alarm of females requires males to assess the nature of the threat in their surroundings whether it demands the recruit the male to ensure group defense against possible predators.

The team also observed that female putty-nosed monkeys only cease their alarm calls when males resonate anti-predator defense calls; signaling that alarm-calling strategies depend on the sex of the signaler.

The symbiotic relationship in members of the putty-nosed monkeys is seen when females recruit males for protection. Males, on the other hand, reassure the females of the quality of their predation defenses to assure future reproduction opportunities.

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Male Calls and Mate Choices

Males emit a general "pyow" call when approaching the rest of the group to advertise their commitment to serving as 'hired guns. The call contains brief information on the events in the surroundings while cueing into the male's identity, like a signature.

Hearing the "pyow call" females can determine which males have higher quality group defense against predators even from a distance. Researchers speculate that this contributes to long-term male reputation within the groups, which would equip females to select the right males to ensure their offspring's survivability.

Frederic Gnepa Mehon, lead author and researcher from WCS's Congo Program explains that as the team observed forest guenons, behaviors suggest that if male putty-nosed monkeys do not prove themselves to be good protectors, they are likely to leave the group earlier than good defenders.

Researchers identify a new call type that was recorded named "kek". The team found that males used "kek" calls when exposed to moving leopard models created by researchers for the experiment.

Previous studies on putty-nosed monkeys in Nigeria have not reported on "kek" calls which signal that the new type of call could be population-specific or uttered towards moving threats.

If "kek" calls are population-specific, then it would equate to the existence of various dialects within the species, which would also be an indicator for vocal production learning.

Claudia Stephan, co-author and researcher from WCS"s Congo Program says that mate selection may play a far more vital role in the evolution of communication than previously thought.

Authors of the study say that current results advance the understanding of various female and male alarm calling in terms of sexual dimorphisms and call usage.