Female monkeys use male monkeys as ‘hired guns’ to protect themselves

According to new research, female monkeys use males as ‘hired guns’ for defense against predators.  More specifically, the research team discovered that female monkeys use alarm calls to recruit males to defend them from predators.

The results promote the idea that females’ general alarm requires males to assess the nature of the threat and that it serves to recruit males to ensure group defense. Females only cease the alarm call when males produce calls associated with anti-predator defense. Results suggest that alarm-calling strategies depend on the sex of the signaler. Females recruit males, who identify themselves while approaching, for protection. Males reassure their female of their quality in predation defense, probably to assure future reproduction opportunities.

Males advertise their commitment to serve as hired guns by emitting general “pyow” calls while approaching the rest of their group — a call containing little information about ongoing events, but cues to male identity, similar as to a signature call. Hearing his “pyow” call during male approaches enables females to identify high quality group defenders already from a distance. This might contribute to long-term male reputation in groups, which would equip females to choose males that ensure their offspring’s survival most reliably.

 “Our observations on other forest guenons suggest that if males do not prove to be good group protectors, they likely have to leave groups earlier than good defenders. To date, it remains unclear whether female guenons have a saying in mate choice, but our current results strongly suggest this possibility.”

-Frederic Gnepa Mehon of WCS’s Congo Program and the Nouabalé-Ndoki Foundation

The bottom-line:

Female putty-nosed monkeys’ alarms may contain little information, but they do so by purpose, namely to facilitate the manipulation of male behavior.

Journal Reference: Frederic Gnepa Mehon, Claudia Stephan. Female putty-nosed monkeys ( Cercopithecus nictitans) vocally recruit males for predator defense. Royal Society Open Science, 2021; 8 (3) DOI: 10.1098/rsos.202135