Mark Bowler/Science Source

Anthrax-carrying flies follow monkeys through the forest

Humans aren’t the only primates flies follow around. The insects tail monkeys, too, according to a new study, and they can carry deadly pathogens such as anthrax.

Researchers followed a group of approximately 60 wild sooty mangabeys (their relative, the gray mangabey, is pictured), small furry monkeys with light-colored eyelids and long slender arms and legs, in the tropical rainforest of Taï National Park in Ivory Coast. They caught flies within the group of mangabeys and at distances up to 1 kilometer away. The researchers found about eight to 11 times more flies inside the group than in the rest of the forest. The same was true for three different groups of chimps.

Next, the team gently dabbed nail polish on nearly 1600 flies to find out whether the same group of insects followed the mangabeys, or whether the primates attracted different flies as they moved through the trees. The marked flies kept turning up around the mangabeys, even 12 days later when the group had moved more than 1 kilometer away, the team reports in Molecular Ecology.

Nearly 12% of the flies carried sylvatic anthrax, which causes more than 38% of wildlife deaths in rainforest ecosystems. The researchers hypothesize that flies could be at least partially responsible for the persistent spread of the disease, which is transmitted by a different microbe from the type of anthrax that infects people. A few flies also carried the bacterium that causes yaws, a disfiguring skin disease that affects both humans and animals.

Next, the team will explore whether flies follow groups of hunter-gatherer humans around, and whether these fly behaviors have caused primates to change their own behavior over time. Although mangabeys are known to use tools, researchers have not yet observed them wielding fly swatters.

*Correction, 12 July, 3:55 p.m.: The original picture that ran with this item was of a chimpanzee, not a monkey. The image has been updated.