New research suggests that female dusky titi monkeys may have evolved a unique mating strategy to outlive males, who die early as a result of the stress and injuries they endure over a lifetime of mating.
Dusky titi monkeys (Callicebus moloch) are small, monogamous primates that live in the rainforests of Brazil. Males and females look very similar, with fur that is mostly gray or brown. They’re often mistaken for each other and are difficult to tell apart. They are also the only primate species known to be polygynandrous, meaning that males and females mate with multiple partners.
Scientists have known for a while that female dusky titis live significantly longer than males, with females typically living into their late teens or even early twenties while males rarely make it past 10 or 12 years old. Females who live longer might be able to produce more offspring, passing on their genes and contributing to the longevity of their species. But scientists are still debating the reasons for the dramatic difference in lifespan between the sexes.
Male Titi Monkeys Experience High Levels of Stress and Injuries
Researchers from the University of Brasília in Brazil set out to find out why dusky titi males died at such a young age. They monitored a group of wild dusky titi monkeys for over 10 years, tracking the health and well-being of both males and females.
The scientists found that male dusky titis were constantly stressed and injured due to constant fights with each other over access to mates and territory.
The researchers found that male titi monkeys had significantly higher levels of stress hormones than females, and they were more likely to suffer from injuries such as bite wounds, broken bones, and infections. This evidence suggests that the high levels of stress and injuries that male titi monkeys experience throughout their lives may lead to an increased risk of early death.
The scientists also observed that female dusky titis were more likely to engage in mate-guarding behaviors, such as staying close to their preferred mates and preventing them from mating with other females. This suggests that females may be using mate-guarding as a way to protect their reproductive partners and reduce the risk of injury and death for both themselves and their offspring.
According to João Paulo Barreto, a researcher at the University of Brasília who led the study, the combination of high levels of stress, injuries, and mate-guarding behaviors observed in female dusky titi monkeys could be contributing to their longer lifespans. Further studies are needed to fully understand the mechanisms underlying the sex-specific survival differences in this species, and how these findings may apply to other primate species.
