Rhesus Monkeys with Redder Skin are More Successful at Breeding

How successful will a monkey be at producing offspring? It turns out that its displayed skin color may be a key indicator. Scientists have taken a look at rhesus macaques and have found that how successfully they breed depends on how they look.

The researchers collected more than 250 facial images of free-ranging rhesus macaques, which are native to Asia and which display red skin coloring around the face. Then, the scientists combined data from these images with 20 years of genetic parentage data to see whether the variation in red skin actually influenced whether a monkey produced more offspring or not.

In the end, the researchers found that males that were more darkly colored and higher ranking in the community had higher fecundity. In addition, skin redness among females was also linked with producing more offspring. Not only that, but monkeys with darker skin coloring were also more likely to produce offspring displaying the same redness; this is actually the first demonstration of heritability of an ornament selected through mate choice rather than fighting in a large mammal.

"Some primates exhibit very noticeable skin colorings, in this case red, that we believe are linked to sexual success," said Lauren Brent, one of the researches, in a news release. "It is not dissimilar to plumage shown by birds-the more striking it is, the more they will be noticed by potential mates. What is fascinating is that we can see that the deeper red coloring that seems to be favored in this species seems to be passed down from generation to generation, which is exciting."

The findings reveal how sexual preference influences how many offspring an animal is likely to produce. While previous studies showed that these monkeys preferred darker red skin, this is the first that shows variation in skin coloration has a genetic basis and can predict reproductive output.

The findings are published in the journal Proceedings of the Royal Society B.