What do animals do when they get sick? They can't go to the doctor's office. They can't go to the pharmacy. Heck, they can't even go online.
Nevertheless, a surprising number of wild creatures have figured out ways to use herbs, resins, and even alcohol and nicotine for health's sake.
Scientists review the ranks of animal pharmacists in the latest issue of Science.
First on the list: primates, who are particularly good at exploiting the medicinal properties of plants. Chimpanzees, bonobos, and gorillas have all figured out that swallowing rough leaves can purge their intestines of parasites. And chimps plagued by roundworm infections have been known to eat plants with anti-parasitic properties, despite their bitter flavor and lack of nutritional value.
These primates seem to know what they're doing, says Jaap de Roode, an assistant professor of biology at Emory University and lead author of the article.
Primates "are not so different from us," de Roode tells Shots. "They can learn from each other and they can make associations between ... taking medicinal plants and feeling better."
But de Roode points out that not all animals self-medicate consciously. Sometimes, the behavior is innate — the result of natural selection.
"People used to believe that you had to be very smart to [self-medicate]," says de Roode. But even insects use substances to keep themselves and their offspring healthy, he says.
De Roode's team studies the behavior of infected monarch butterflies. When given the choice, these infected butterflies will lay their eggs on anti-parasitic milkweed, thus protecting their offspring from infection. Healthy butterflies don't display this preference.
"I wouldn't say it's a conscious choice, but it's a choice," says de Roode.
Plenty of other insects employ strategies to avoid and treat infection. Take the woolly bear caterpillar, for example, which ingests plants that are toxic to parasites. Or the wood ant, which incorporates antimicrobial resin into its nests. And don't overlook the crafty fruit fly, which lays its eggs in alcohol from fermented fruit to protect its little ones from parasitic wasps.
Birds have a few medicinal tricks up their sleeves too. In cities, house sparrows and finches have been known to add cigarette butts to their nests, which can help to reduce mite infestations. (Nicotine is an effective bug repellent.)
According to de Roode, it's important for scientists to understand how animals defend against parasites: It can affect how we model diseases in wildlife populations. It can also affect human food production.
For example, some bees stay healthy by covering their hives in antimicrobial tree resin. But beekeepers tend to weed out these messier, resin-collecting bees, thus potentially decreasing the overall health of the hive.
And, of course, understanding how animals medicate themselves could also lead to insights for human health. "It may actually open our eyes to finding drugs that we could potentially use," says de Roode. After all, animals "have been studying medicine much longer than we have."