Evidence for deceptive fertility in a wild primate

Area of Science:

• Primate reproductive strategies
• Animal communication and deception
• Sexual conflict and infanticide

Background:

• Animal signals often convey reliable information, but deception can evolve under conflicting interests, particularly in mating contexts.
• Male takeovers in gelada (Theropithecus gelada) populations are frequent and often result in sexually selected infanticide, posing significant risks to lactating females and their infants.

Purpose of the Study:

• To investigate whether female geladas engage in deceptive fertility signaling as a counterstrategy against infanticide.
• To determine the hormonal mechanisms and demographic consequences of deceptive signaling in response to male takeovers.

Main Methods:

• Analysis of 14 years of demographic data and fecal hormone levels (estrogen) from wild gelada populations in Ethiopia.
• Correlation of female sexual swelling resumption, conception timing, and infant survival with male takeover events.
• Examination of estrogen surges in lactating females following male takeovers, irrespective of infant age.

Main Results:

• Lactating female geladas resumed sexual swellings and mated with new males post-takeover, but took significantly longer to conceive compared to females cycling at other times.
• Females displaying post-takeover sexual swellings had a reduced likelihood of infant infanticide.
• Fecal hormone analysis revealed elevated estrogen levels after takeovers, even in females with very young infants, suggesting mediation of both fertile and non-fertile swellings.

Conclusions:

• Female geladas deceptively signal fertility (exhibiting sexual swellings when conception is unlikely) as an adaptive counterstrategy to mitigate the risk of infanticide.
• Sexual swellings in geladas can serve a dual function, signaling both true and false fertility states, influenced by estrogen levels.
• This study provides evidence for deception in animal signaling within the context of sexual conflict and infanticide avoidance in primates.