Chimpanzees and other primate species in Uganda's Kibale National Park are facing a concerning issue as they are being exposed to a mixture of harmful chemicals. A recent study discovered significant levels of pesticides and flame retardants in the feces of four primate species, including chimpanzees and red colobus monkeys, indicating that these pollutants may be affecting their health and development.
The study revealed that female primates and their young were particularly affected by these chemicals. The researchers observed higher levels of stress and reproductive hormones in these animals, implying that the compounds could disrupt their bodily functions and potentially hinder their growth and development.
Tessa Steiniche, the lead author of the study and a Ph.D. student, expressed concern about the impact of endocrine disruption in juvenile primates. Exposure to these chemicals during critical developmental periods can have long-lasting effects on their well-being.
The researchers caution that the chemicals examined in this study may only represent a fraction of the pollutants affecting these primates. They suggest that there are likely more compounds present that could be impacting their health.
The unfortunate reality is that being in a “protected” area does not shield these primates from chemical pollution. Human activities in and around the park, including tourism and research, can introduce potentially harmful chemicals, further exacerbating the issue.
Tessa emphasizes that the study merely scratches the surface in understanding the range of chemicals these primates encounter in their environment.
The study's findings were published in the journal Biology Letters.
The impacts of chemical pollution on wildlife
In recent times, pollution has reached unprecedented levels worldwide, affecting our lives in ways we have yet to fully grasp. One of the most well-understood forms of pollution is chemical pollution, with numerous studies shedding light on its effects at various levels.
For instance, antibiotics present in water have been found to hinder the growth of algae by limiting their ability to perform photosynthesis.
On the other end of the spectrum, chemicals like polychlorinated biphenyls (PCBs), previously used as coolants, have been observed to impact killer whales. These substances accumulate in the whales' blubber and can interfere with their immune system and reproductive abilities.
However, previous research methods employed to study these effects have had their limitations. Laboratory experiments often fail to account for the impact of chemical mixtures on health, while samples from deceased animals tend to have significantly higher pollutant levels than average.
To overcome these challenges, scientists have turned to biomonitoring techniques in recent years, enabling them to study wild animals in their natural habitats. In the current study, researchers collected fecal samples from four primate species residing in Kibale National Park: chimpanzees, olive baboons, red-tailed monkeys, and Ugandan red colobus monkeys. This approach allowed the scientists to measure not only the levels of pollutants but also the hormones that may be affected by them.
“Fecal biomonitoring offers a valuable approach to toxicology, aligning with the growing focus on animal ethics,” explains Tessa. “Although fecal samples may not be the cleanest matrices to work with, the opportunity to study the impacts of pollution on wild animals without causing harm or manipulation is remarkable.”
How are primates affected by chemical pollutants?
The researchers conducting the study discovered a staggering 97 different pollutants in the fecal samples of the primates. These pollutants were categorized into three main groups: organochlorine pesticides (OCPs), brominated flame retardants (BFRs), and organophosphate esters (OPEs) commonly used in plastic production.
It is suspected that the animals were exposed to these compounds by foraging in farms located near the national park for food, as well as encountering electrical and plastic waste within the forest.
Certain chemicals were found to be particularly prevalent in primate feces, with one specific BFR appearing in over 70% of samples from all four species. Studies on mice have shown that mammals exposed to BFRs at a young age struggle to eliminate the chemical efficiently, suggesting that BFRs may be accumulating in these primates, putting them at a higher risk of more severe health effects.
Younger animals are believed to be more vulnerable, as higher levels of BFRs in juvenile primates were associated with decreased levels of the sex hormone estradiol and increased levels of the stress hormone cortisol.
Although there are relatively few studies on the effects of these chemicals on mammals, they have been linked to issues such as liver damage, reduced hormone production, impaired brain development, and compromised immune systems.
For endangered species like chimpanzees, these findings impose additional challenges on populations already facing significant pressure. The researchers hope that future projects will build upon this study to gain a better understanding of contamination levels in other wildlife species and determine the extent of their impact.
Tessa expresses the team's interest in further investigating the sources of chemical exposure in Kibale and exploring why certain species are more or less susceptible to specific pollutants. Additionally, incorporating social dimensions into research is crucial to empower surrounding communities with the knowledge and resources needed to make informed decisions regarding chemical use and disposal.
Source: Natural History Museum