Northern muriquis are one of the world’s most endangered monkey species and are on the edge of extinction, thus raising healthy offspring is vital for their long-term survival. The feces of these monkeys is now being studied by researchers in order to acquire a better knowledge of how they choose their mates and gain insights into their mating lives.
The scientists coupled genomic research with long-term behavioral observations in a paper published on August 2 in the journal Proceedings of the Royal Society B to better understand the reproduction processes of the endangered species. Muriquis, in contrast to most primates, live in peaceful, egalitarian groups centered on related males and their mothers.
Karen Strier, a co-author of the paper and a professor of anthropology at the University of Wisconsin-Madison, who has been studying the behavior and ecology of these monkeys in a small, preserved section of the Brazilian forest for the past 40 years, said she and her team can now identify each of the monkeys as well as whose poop is whose.
She and her colleagues collected the samples and delivered them to Anthony Di Fiore, an anthropology professor and director of UT Austin’s Primate Molecular Ecology and Evolution Lab, and Paulo Chaves, Di Fiore’s Ph.D. student at the time. They then used these samples to investigate the DNA in order to better understand muriqui mating behavior.
Because Strier’s field crew understood which samples belonged to whom, the study team was able to pose novel genomic questions. “I knew from behavioral observations that there was a lack of competition in mating and that mothers didn’t mate with their sons or close male relatives. But the only way to know who the fathers are is with genetics,” Strier said.
Females prefer to mate and reproduce with men who have a diverse range of coding genes
Following their lab investigation, Chaves and Di Fiore confirmed that there were no mother-son pairings, implying that muriquis may recognize their family members, allowing them to avoid incestuous mating. Female muriquis prefer to mate with males who have a more diversified set of genes coding for chemicals that play a crucial role in the body’s immune response to infections and other environmental stressors, according to their research.
The major histocompatibility complex (MHC) is an intriguing class of genes that Chaves and Di Fiore were able to define genetic diversity between individual monkeys. “Our finding that male sires have higher MHC diversity than expected by chance is one of the things we would expect if that diversity contributes to male fitness or is one of the dimensions of female mate choice,” Di Fiore said. “Our study is one of just a handful that has looked at the relationship between MHC variation and reproductive patterns in wild primates and is the only one to do so for an egalitarian species like Muriquis,” she added.