While studying capuchin monkeys in Costa Rica, Mary Baker observed that the cat-size monkeys like to rub themselves with lemons, limes, and oranges. They kind of saturate their bodies when they really get into it, says Baker, a primatologist at the University of California at Riverside. It’s an amazing sight. They’re rubbing and hugging the fruit, biting into it, drooling like crazy, there’s spit flying everywhere- -whenever I show people videotapes they always think it’s on fast-forward. The monkeys also rub their fur with clematis-vine stems and piper-plant leaves. Indigenous people in Central America use these same plants to treat skin ailments and to stop bleeding; citrus fruits in particular contain antibacterial compounds and may also repel insects. Baker noticed that when she rubbed herself with fruits (The only part I didn’t do was drool, she says), mosquito-bite scabs healed faster. Capuchins are intelligent, but are they really playing doctor? Just as it’s an evolutionary advantage to be able to recognize and avoid toxic plants, says Baker, it could also be advantageous to know medicinal plants. Of course, the monkeys may simply enjoy the sensation. Baker knows of one captive monkey that enjoys rubbing itself with lemon-flavored Gummi Bears. I’m still trying to figure out why they do it, says Baker. I wish I could just ask them.