Zoo Diets Are Making Monkey Gut Bacteria More Human-Like

red-shanked douc munching away on some zoo food. jeep2499/Shutterstock

It’s hardly news that many people don’t eat enough fruit and vegetables. However, it turns out we're inflicting this bad habit on monkeys held in zoos – and it’s having a strange effect on their gut bacteria biome.

A recent study led by the University of Minnesota has found that monkeys in zoos appeared to have their gut flora “humanized”. The full study can be found in the most recent issue of the Proceedings of the National Academy of Sciences.

The researchers collected poop samples from dozens of highly endangered red-shanked doucs and mantled howler monkeys from zoos across three different continents. They then used these samples to sequence the DNA of their gut bacteria and compare it to the biome found in a wild counterpart.

The analysis showed that the captive monkeys had almost totally lost their native natural gut bacteria. Instead, their guts were dominated by the same bacteria that dominate the human digestive system, such as species of Bacteroides and Prevotella.

This alone could be due to a whole number of factors, such as geography, genetic differences, or antibiotic use. However, they also noticed that the wild monkeys' poop contained up to 40 percent plant DNA, while the captive monkeys' contained nearly none. This led the researchers to conclude that a lack of fruit and vegetables in their diet was the main cause.

They tested this out by conducting the same tests on a "semi-captive" population of red-shanked doucs from a Vietnamese sanctuary who eat a diet that contains around half the variety of plants eaten by wild doucs. Sure enough, this sample had a microbiome right in between those of the wild and captive doucs.

While this might sound like how Planet of the Apes becomes a reality, the real concern is about the health of the monkeys. Gut bacteria in humans is linked to a host of diseases and conditions, including obesity, anxiety, and depression.

"We don't know for certain that these new modern human microbes are bad, but on the other hand many studies are now showing that we evolved together with our resident microbes," study author and professor Dan Knights said in a statement. "If that is the case, then it is likely not beneficial to swap them out for a totally different set."


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