Primates living in Uganda have 97 chemical pollutants in their digestive tracts, some of which were linked to hormonal changes in female and young primates.
Chemical pollutants have reached every corner of our planet, making exposure to these often harmful substances in air, food and water almost inevitable for humans and wildlife. To determine their impact on wild primates, the researchers used a minimally invasive sampling method: the collection of droppings.
Over two months in 2017, Tessa Steiniche at Indiana University and colleagues collected a total of 71 fecal samples from chimpanzees (Pan troglodytes), baboons with olives (Papio anubis), red colobus (Piliocolobus tephroscele) and red-tailed monkeys (Cercopithecus ascanius) in Kibale National Park in Uganda.
The researchers tested the poo using chemical analysis and found 97 pollutants, most of which are known to disrupt the functioning of hormones in mammals. Pesticides and flame retardants, both present in the samples, are examples of such pollutants.
The team also tested hormone levels. Across all species, females who had a higher concentration of pesticides in their feces were more likely to have higher levels of cortisol – a stress hormone that helps regulate metabolism and the immune system. The researchers found a similar pattern in young primates, where higher concentrations of flame retardants in poop were associated with increased cortisol and decreased levels of estradiol, a reproductive hormone.
“Our results showing effects in juveniles are of particular concern,” Steiniche says, because early exposure to these chemicals during development can have lifelong effects. She says the team will need to monitor the primates over the long term to see how these toxins affect their growth and reproduction.
This is a wake-up call for those who view national parks as places free from human influence. “I think we still tend to have an idealized image of wild primates living in beautiful, undisturbed habitats, but the sad reality is that even protected areas aren’t immune to the impacts of pollution,” Steiniche says. .