Nature

How Animals Self-Medicate

June 1, 2016 | Erica Tennenhouse

Bonobo monkey
Photo credit: Kabir Bakie/Wikipedia (CC BY-SA 2.5)

The animal kingdom is full of competent pharmacists.

Any dog or cat owner has probably witnessed animal self-medication. When they have an upset stomach, both dogs and cats will often eat grass to induce vomiting.

In the wild, some of the first documented cases of self-medication were of chimpanzees suffering from intestinal parasites. After chewing the pith of a plant known as bitter leaf and swallowing the leaves whole, the chimps were observed to recover from their ailments. Some of the compounds found in the bitter pith are known to inhibit parasite egg laying and mobility, while swallowing rough leaves whole appears to expel intestinal parasites.

The ability to self-medicate is sometimes assumed to require a level of intelligence that allows animals to make conscious decisions. However, it is becoming clear that self-medication in many animals is an innate rather than learned behavior.

SEE ALSO: Natural High: Animals that Use Drugs in the Wild

Woolly bear caterpillars, for example, can be infected with lethal tachinid flies. Parasitized caterpillars will specifically ingest plant toxins that help them become resistant to the flies. These toxins are harmful to healthy caterpillars, but help those infected by tachinid flies to survive.

In some cases, animals may medicate their offspring or siblings, thus de-emphasizing the “self” in self-medication. Fruit flies prefer to lay their eggs in high-ethanol foods when they detect the presence of parasitoid wasps; the ethanol reduces the chance that their offspring will become infected. Honeybees forage for plant resins, which they use to line the entire hive interior; colonies with resins are less susceptible to being infected by fungal parasites.

Here are some more examples of natural remedies used by animals:

  • African elephants induce birth by chewing on the leaves of a particular tree; Kenyan women brew tea from this same tree to induce childbirth.

  • Tapirs, forest elephants, colobus monkeys, mountain gorillas, and chimpanzees eat clay, which absorbs intestinal bacteria and their toxins to alleviate upset stomach and diarrhoea.

  • More than 200 species of songbirds perform anting, whereby they vigorously wipe ants along the spine of each feather, or sometimes roll in anthills. Birds most commonly use ants that release formic acid, which is thought to protect against feather lice.

  • North American brown bears make a paste of Osha roots and saliva, which they run through their fur to repel insects and soothe bites. This plant contains 105 active compounds that may repel insects when applied topically.

  • Tobacco hornworms ingest nicotine, which reduces bacterial growth and toxicity, leading to increased hornworm survival.

Read next: Fungus-Farming Ants Are Extremely Hygienic

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