Self-Medicating Monkeys Gobble Painkilling Bark

By Jason G. Goldman

When a monkey has the sniffles or a headache, it doesn’t have the luxury of popping a few painkillers from the medicine cabinet. So how does it deal with the common colds and coughs of the wildlife world?

University of Georgia ecologist Ria R. Ghai and her colleagues observed a troop of more than 100 red colobus monkeys in Uganda’s Kibale National Park for four years to figure out whether the rain forest provides a Tylenol equivalent.

Monkeys infected with a whipworm parasite were found to spend more time resting and less time moving, grooming and having sex. The infected monkeys also ate twice as much tree bark as their healthy counterparts even though they kept the same feeding schedules. The findings were published in September in the journal Proceedings of the Royal Society B.

The fibrous snack could help literally sweep the intestinal intruder out of the simians’ gastrointestinal tracts, but Ghai suspects a more convincing reason. Seven of the nine species of trees and shrubs preferred by sick monkeys have known pharmacological properties, such as antisepsis and analgesia. Thus, the monkeys could have been self-medicating, although she cannot rule out other possibilities. The sick individuals were, however, using the very same plants that local people use to treat illnesses, including infection by whipworm parasites. And that “just doesn’t seem like a coincidence,” Ghai says.

University of Helsinki researchers recently announced the first evidence of self-medication in ants. When the biologists exposed hundreds of Formica fusca ants to a dangerous fungus, many of the infected insects chose to consume a 4 to 6 percent hydrogen peroxide solution made available for the experiment. Healthy ants avoided the household chemical, which can quash infections in small doses but is otherwise deadly. The sick ants that partook were less likely to succumb to the grips of the fungus. In the wild, they could perhaps acquire the compound by eating plants that release it to fight aphid infestations.