Zoopharmacognosy: do animals self-medicate?

Zoopharmacognosy is a process where animals use their natural instincts to self-medicate by using plants, soils, and minerals to cure themselves of illnesses or parasites. The word comes from the Greek words "zoos" meaning animal and "pharma" meaning drug or medicine, and "konnosy" meaning knowledge. When animals are ill, they seek out remedies in their environment. They show an amazing capacity for getting better by using plants that have medicinal properties. A common example that most people are familiar with is when a cat eats grass to induce vomiting after it has ingested something poisonous such as insecticides, de-worming medications, or even kitty litter. There is a lot of debate around this topic in the scientific world, since no study has yet proven 100% that self-medication among animals is actually possible.

A 2014 study suggests that the great bustard Otis tarda may consume highly toxic blister beetles to rid its body of gastrointestinal bacteria that cause sexually transmitted diseases. During the mating season, males have been observed to consume increased numbers of toxic beetles, which may even kill them, to reduce the parasitic load, thus increasing their chances of mating. If the assumption that great bustards are deliberately using blister beetles as an oral antimicrobial compound is correct, then this case can be seen as self-healing of the animals, making the concept of zoopharmacognosy more plausible.

In a similar study on woolly bear caterpillars in 2009, researchers concluded that these primitive creatures also use toxins to fight deadly parasites (tachinid flies). The research focuses on observing caterpillars and their consumption of pyrrolizidine alkaloids, which are highly toxic to both caterpillars and their parasites. It turned out that caterpillars infected with parasites were more likely to consume large amounts of the toxin than those that were clean.

Animals with more complex behavior like chimpanzees and dolphins, use a wider range of different substances not only to improve their physical condition but also to achieve an altered state of mind, which might help them cope with stress.

Chimpanzees use leaves of plants like aspilia (a genus of plant that is valued by the Bambuti people for its healing properties) to help heal physical wounds, while mandrills consume plants known to have psychoactive properties, such as iboga root (tabernanthe iboga contains ibogaine, an alkaloid known for its psychedelic and dissociative properties), before engaging in a turf fight with each other. Dolphins are known to seek out certain pufferfish that contain a toxin called tetrodotoxin, and chew on them. The toxin causes paralysis which can sometimes last for several hours.

There were reports of elephants becoming intoxicated after eating marula fruit. However, it was determined that it is extremely unlikely for an elephant to consume a rotten fruit, since too many other animals also love this fruit and will not allow it to rot. It has also been roughly estimated that an elephant would need to eat about 25 kilograms of rotten fruit to get a little drunk, which is highly unlikely.

Zoopharmacognosy remains a controvercial topic in the scientific community. Some scientists believe that the observed behaviors are nothing more than animals eating plants that they happen to like the taste of, and that there is no medicinal value to them. Others believe that the animals are sensing some sort of therapeutic effect from the plants and that further study is warranted. More research is needed to determine whether or not zoopharmacognosy is a real phenomenon and to identify the specific mechanisms involved. So far, only a small number of studies have been conducted on this topic, so there is still a lot we don't know.