Carl Zimmer in his excellent blog, The Loom:
Animals, as I explained in my recent column for Discover, take precautions not to get sick (including the famous anal cannon). We take precautions too–conscious ones, based on what we have learned about how diseases spread, and perhaps also unconscious ones that lower our risk of infection.
But if those precautions fail, we humans sometimes take medicines to kill off the pathogens making us sick. And there’s an intriguing body of evidence suggesting that animals take medicine too.
A lot of that evidence comes from studies on chimpanzees, our closest living relatives. When they get infected, they will sometimes devour leaves and other vegetation they otherwise never touch. In the case of one plant, the chimps have to first peel away an outer covering that is lethally toxic. They go to these lengths, it appears, because eating these plants can cure them of their ills. Some plants can flush parasites out of the gut and others actually fight the pathogens themselves. In fact, when researchers study the plants chimpanzees eat, they discover new compounds that kill bacteria and other pathogens. They look promising as medicines for people. (pdf).
Given the sophisticated minds of chimpanzees (they can, for example, plot rock-hurling attacks on zoo-goers), it’s possible that chimpanzees teach themselves which medicinal plants to take, and these medical traditions spread culturally. But other animals seem to eat peculiar things when they get sick, too. Even insects do. Obviously, no invertebrate has ever graduated from medical school. (Insert your doctor joke here.) So the question arises, are insects actually self-medicating, or are they getting so sick that their diet goes haywire?