In Mexico City, house sparrows and house finches are picking up cigarette butts and weaving individual fibres into the lining of their nests. When researchers first discovered the butts – while studying what plastics end up in nests – they assumed it was simply a fluffy material being used as insulation. But through a series of ingenious tests, they discovered that the butts were actually medicinal: the birds actively collected them because the toxin nicotine reduces mites and other blood-sucking parasites. The birds are treating themselves – and their offspring.
It’s one of many fascinating examples of animals medicating themselves revealed in Doctors By Nature, a new book by the US-based Dutch academic Jaap de Roode. Apes deliberately swallow leaves to dislodge intestinal worms. Caterpillars switch diets to repel parasitic flies. Bees incorporate sticky resins in their homes to combat disease.
