Of Monkeys and Millipedes

From the December issue of CEI UpDate

“I would much rather be descended from an ape, sir, than a bishop.” — Attributed to T.H. Huxley

The recent news about the wedge-capped capuchin monkeys causes me to feel quite kindly toward the thought of being descended from prehensile-tailed primates. Wedge-capped capuchins in Venezuela, it turns out, actually use insect repellant. Not only do individual monkeys use it, they share it with all members of the group. “Monkeys before mosquitoes!” seems to be their byword, a catch phrase that humans would do well to emulate.

Here’s the story: Scientists recently noted some unusual behavior in a group of capuchin monkeys in Venezuela. The capuchins seek out, in branches and termite mounds, a particular species of millipede. Once possessed of such a prize, a monkey rubs the millipede all over its fur and then passes it on to another monkey. Occasionally one will break up the routine by popping the bug in its mouth, but the monkey eventually spits out it, and the anointing continues until the entire group reeks of eau d’millipede.

This behavior is unusual, not just because monkeys are smearing themselves with bugs, but because in all other group matters, such as feeding and grooming, wedge-capped capuchins are strict hierarchists. The top bananas get the best bananas. Yet the group shares the millipedes equally, ignoring the hierarchy that dominates the rest of capuchin life.

Intrigued by this peculiar behavior, scientists investigated why capuchins act in such atypical fashion. They analyzed the millipede secretions and discovered that they are loaded with benzoquinones, which offer several protections to the millipede. Not only do they taste awful, but they cause intense pain in the mouth of the eater. One of the scientists who analyzed the secretions put a millipede in his mouth and “immediately fell to his knees, it was so painful and irritating.” Yet monkeys will put the millipedes in their mouths before anointing themselves with the secretions.

Why do they subject themselves to the excruciating taste and feel of benzoquinones? The scientists believe the answer lies in another chemical characteristic of benzoquinones. Benzoquinones are potent insect repellants, many times more powerful and more toxic than the deep woods repellant used by the US Army. By mouthing the millipede, the monkeys stimulate it to produce more secretions–more insect repellant that they can apply to their fur.

The monkeys need a potent insect repellant. Like many mammals in South America, the wedge-capped capuchins can harbor bot fly larvae. Bot flies lay their eggs upon the abdomen of mosquitoes. When a mosquito lands to feed, the heat of the mammal hatches the eggs. The bot fly larvae wiggle beneath the skin of their mammalian host and live there for about six weeks, causing large painful lesions on the host.

While bot fly larva infestations are not necessarily lethal, they are extremely painful. Multiple lesions also weaken a monkey’s immune system, compromising its ability to fight off other infections. Also, bot fly lesions can attract screw worm flies. Screw worm flies lay their eggs near lesions. The hatched larvae then feed on living flesh, killing off massive amounts of tissue and eventually the animal itself. By applying benzoquinones to their fur, the monkeys may prolong their lives by warding off mosquitoes and the pests that they carry.

Unable to set up factories that can produce vast quantities of OFF, monkeys are forced to resort to manipulating what parts of the natural world upon which they can lay their hands. Humans can build factories to produce pesticides and repellants, yet many among us don’t seem to have even the inherent intelligence of the capuchin monkey.

During the West Nile outbreak this past summer, activist groups opposed spraying pesticides that would kill the virus carrying mosquitoes, claiming that the chemicals were deadlier than the disease. They argued that the most we should do to protect ourselves from deadly mosquitoes would be to use insect repellants to ward off the biting horde. But it’s hard to get a hold of insect repellants when activists want them banned as well. In 1992 , for example, New York banned all products containing DEET concentrations over 30 percent (DEET is the active chemical ingredient in most commercial insect repellants). Although the ban was lifted under the Pataki administration, the calls for banning DEET with concentrations over 30 percent continue, even though studies have shown that DEET concentrations between 30-50 percent are the most effective for warding off ticks. That’s a pertinent consideration in New York, where 4,640 cases of Lyme Disease occurred in 1998.

The old Bing Crosby standard “Swinging on a Star” had the line, “All the monkeys aren’t in the zoo, Every day you meet quite a few.” Capuchins find the use of pest repellant so important that they ignore the group hierarchy and share with all. Some humans, on the other hand, are far less charitable. They want to establish a hierarchy that denies pesticides and repellants to those who need them to protect themselves from insects and disease. In the end, there are more monkeys in the cities of United States than there are in the jungles of Venezuela.