Cavities, high cholesterol, triglycerides (a type of fat found in the blood and adipose tissue of the body), and high blood glucose levels (the amount of glucose or sugar in the blood).
These diseases, very common in humans, have been identified in white-faced monkeys in Manuel Antonio National Park in the Central Pacific, although to a lesser extent in marmosets and howler monkeys. Monkeys were also found with dark teeth, dull fur, and bumps or spots on their bodies.
A study that began in 2012 by a team from the International Institute for Wildlife Conservation and Management (Icomvis-UNA) made these and other findings in Costa Rica’s main national park (with an annual visitation of more than 478,000 people in 2023).
Laura Porras, an academic and researcher at Icomvis-UNA, explained to El Observador that the study also revealed that raccoons had stopped being primarily nocturnal and had adopted daytime schedules. And, unfortunately, some individuals also appeared to have high cholesterol.
But there’s more: in a necropsy or autopsy performed on a monkey (which she witnessed), numerous parasites commonly found in the human body were found in the animal’s stomach.
Among them were Plasmodium spp (the parasite that causes malaria), CHIKV (chikungunya virus), Mycoplasma spp, and Trypanosoma spp (which causes Chagas disease).
Diurnal Raccoons
Porras—who conducted the work with her colleague Grace Wong and Mauricio Jiménez, a veterinarian at the UNA—explained that the raccoons were studied in a small population, fitted with radio collars, and later used camera traps.
Thanks to these devices, it was determined that the raccoons changed their habits, at least during the period from 2012 until the pandemic. Obviously—the academic adds—it cannot be ruled out that this change began long before 2012.
During that period, findings were also made with white-faced monkeys—also known as capuchin monkeys or white-faced monkeys—which are the primates with the largest number of specimens in Costa Rica.
And the answer is…
But why did the raccoons change their habits and the monkeys develop numerous human diseases? The answer is simple: humans gave them food, or they managed to acquire it. Even more serious: these are foods that are unsuitable for wild animals.
The researcher mentioned sandwiches, snacks, cookies, and even bananas. Although bananas are not part of their diet, people believe they should not eat them, as they can be harmful, Porras noted.
“At the health level, in several individuals, there was a positive correlation between the presence of infectious agents and changes in blood tests. Some of the changes may be due to the habitat and the likelihood of exposure to food of human origin, which translates into dietary imbalances and behavioral changes,” the specialist explained.
And what happened after the pandemic?
The researcher emphasized that, although records aren’t as robust as those compiled before the pandemic, it is known that the raccoons returned to being nocturnal.
The reason is simple: no humans gave them food or left food lying around. However, she has reported some sightings of raccoons present during the daytime upon the return of visitors to the park.
And the reality is the same with the monkeys: the white-faced monkeys continue to enjoy the food given to them by those who come to this protected area, despite the fact that feeding them is prohibited. Starting in October 2023, with the cage, this has been reduced to a minimum, Porras assured.
Fine for feeding
It is worth remembering that the Costa Rican Wildlife Conservation Law (Law No. 7317) prohibits feeding wild animals. This provision seeks to prevent damage to ecosystems and the species themselves.
This is because food provided by humans can alter natural behavior, affect their health, and create dependency. Feeding wildlife can also cause ecological imbalances and conflicts with humans, the law states.
Finally, the law provides for fines that can reach ¢140,000 for this violation. Porras indicated that among the efforts made to minimize and even eradicate the intentional or accidental feeding of monkeys or raccoons, a violation took place in 2023.
In October of that year, two closed metal structures (like cages) were placed: one around the soda and another next to a table area. “Tourists come in, close the door, eat there, all inside. Garbage management is done internally, and then they leave without food,” Porras emphasized. However, some tourists still manage to move food out of these cages.
However, more measures are needed. This one is insufficient, he says. “In addition to raising awareness among visitors to these sites about not feeding the animals, there should be more signage and even a Tourist Police presence. We need to educate more to raise greater awareness of the damage we are doing to wildlife,” Porras said.
This same awareness—he emphasized—should extend to lodging establishments, bars, and restaurants where monkeys like marmosets frequently come. The same applies to those who frequently visit the beaches and feed the animals.
