Can animals heal themselves?

Explore the self-medicating abilities of animals, from chimpanzees eating bitter leaves to caterpillars foraging for poisonous plants. Could these behaviors hold the secret to their survival?

This is not the only animal that uses plants to treat diseases.

Treatment of disease

In 1987 in Tanzania, a chimpanzee named Chausiku did something that surprised scientists. One day, they discovered that Chausiku was chewing on the bark of a bitter leaf plant, also known as bear bile, which is not part of the animal's diet. Bitter leaf is a traditional medicine in Africa, used to treat malaria, diabetes, digestive diseases such as loss of appetite, dysentery and digestive disorders.

Chimpanzees know how to use leaves to cure diseases.

Michael Huffman, a primate researcher at Kyoto University in Japan, speculated that Chausiku was self-medicating because he had been lethargic and had lost his appetite for several days. After 22 hours of eating bitter leaves, Chausiku returned to a healthy, energetic state.

Scientists examined and discovered that Chausiku was infected with intestinal worms and that eating bitter leaves was a scientific record of animals self-medicating.

According to Huffman, scientists can only speculate based on observing and measuring the results of that action. In addition, they will rely on innate physiological factors such as cravings for certain flavors or some social behaviors such as animals noticing that pain is reduced after a certain action and repeating that behavior. Therefore, more and more scientists believe that animals, especially some species closely related to humans, know how to use medicine to treat diseases.

In 1993, biologist Michael Singer, Wesleyan University (USA), observed woolly bear caterpillars gnawing on many different types of plants. This is an unusual behavior for caterpillars because this species only gnaws on certain types of leaves.

It turns out they are infected with parasites. The caterpillars' behavior is not random but purposeful. Specifically, they are seeking out poisonous plants such as echinacea, which contain the toxic alkaloid pyrrolizidine.

Singer initially did not believe the caterpillars were healing. However, research has shown that the caterpillars have four taste buds, and one of them can sense the alkaloid pyrrolizidine and make the chemical taste better.

Caterpillars will seek out leaves containing this toxin if they are infected with the parasite. Experiments have shown that caterpillars that eat the pyrrolizidine alkaloid have a better chance of survival, although the toxin is still dangerous to healthy ones.

This got Singer thinking about the side effects of drugs on humans, which convinced him that animals would also seek out treatments.

Capuchin monkeys , which live in Central and South America, don't want to be itchy and infected with ticks and mosquitoes. So they will catch the centipede Orthoporus dorsovittatus , crush it in their hands, and coat their fur with the slimy substance inside the centipede's body.

This behavior is common during seasons when mosquitoes are most active. In 2003, scientists discovered that the slime in centipedes is benzoquinone, which repels mosquitoes.

'This behaviour doesn't mean that the monkeys know what they're doing. They may just do it because it feels good, but we know that this behaviour can protect against stings and infections,' said evolutionary biologist Jacobus De Roode, Emory University (USA).

In 2022, scientists discovered 19 cases of chimpanzees tending to wounds by crushing insects. In one instance, a female chimpanzee caught an insect and gave it to a male chimpanzee, who then applied it to another male's open wound.

This action is not necessarily to help the wound heal quickly, but may be a common social behavior of chimpanzees. But considering the 'injured' state, this can be considered a self-healing measure in chimpanzees.

Urban birds spread tobacco threads in their nests to prevent ticks.

Disease prevention

Animals also know how to prevent disease. Constantino de Jesús Macías García, a behavioral ecologist at the Universidad Nacional Anutónoma de México, discovered that birds in Mexico often use tobacco to build their nests. Because nicotine, contained in tobacco fibers, repels parasites that harm the garden . Birds will pick up cigarette scraps and spread them on their nests.

Based on the findings, Constantino's team conducted experiments with more than 50 nests of house sparrows and local sparrows. The results showed that nests with smoked cigarette butts had fewer mites, lice, and fleas than nests without cigarette butts.

Cellulose is a naturally occurring, non-biodegradable plastic that repels insects.

This is a form of disease prevention for urban birds. Tobacco is used instead of aromatic plants that are available to these birds in the wild.

Similarly, when monarch butterflies are infected with the parasite Ophryocystis elektroscirrha, they will eat plants containing cardenolide , a toxin that kills the parasite in their bodies. In addition, after becoming monarchs, many will lay eggs on toxic plants containing cardenolide, reducing the chance of their eggs becoming infected.

'We can believe that these mothers are trying to protect their babies. Or they are unaware that they are infected and their bodies, when infected, prefer bitter plants ,' said Mr De Roode.

According to this expert, the use of drugs in the animal world is more common than scientists think. This proves that animals will always find ways to survive, not only by finding food and hunting, but also by preventing and treating diseases. And plants will open up opportunities for scientists to study how to care for animals in the future.