Chimps self-medicate under human pressure

Jun 21, 2012 by Tom Marshall
Chimps self-medicate under human pressure

Chimpanzees living in small fragments of forest close by people and farm animals are turning in increasing numbers to natural remedies in an effort to deal with their stressful and disease-prone existence, a new study suggests.

Scientists already knew the respond to seasonal intestinal by swallowing the leaves of particular forest plants whole. The rough leaves seem to have a purgative effect, causing them to excrete the parasites and soothing sore guts.

But this rudimentary was never meant to handle the kind of pressure that are now facing as human farms and settlements eat into their . Stressed by encounters with humans and exposed to new infections, they are self-medicating more than ever, but it doesn't seem to be keeping them healthy.

Researchers focused on living in Bulindi, Uganda, where a few fragments of forest remain amid villages and farmland. They monitored the apes' routes through the forest and regularly sampled their , which they inspected for the whole leaves, as well as like nematodes and tapeworms.

They found that these so-called 'village chimpanzees' suffer from multiple parasite infestations, and are swallowing leaves far more often in response. 'At other sites it's rare to find the undigested leaves in more than one or two in 100 dung samples,' says Dr Matthew McLennan, a specialist at Oxford Brookes University in interactions between chimps and humans, and the lead author of the paper. 'At Bulindi it was more like one in ten. So it's happening at a different order of frequency than in less disturbed landscapes.'

Chimps self-medicate under human pressure
Leaves from the forest herb Aneilema nyasense. Covered in bristly hairs, the leaves are thought to irritate chimps' guts when swallowed whole, acting as a purgative.

It could be that the chimpanzees are picking up new parasite infections from people and . In one case, a chimp was found to be carrying a kind of tapeworm normally seen in chickens; McLennan suspects it wasn't truly infected, and had merely preyed on a domestic fowl not long ago, but this still highlights the potential for chimps to be exposed to new pathogens through contact with human civilisation. He also notes that the risk goes both ways; it's possible that dangerous new diseases could make the leap from chimps to humans when the two species are living cheek by jowl.

It's also possible that the apes simply find existence stressful with their habitat changing so quickly and with so many humans around - aggressive confrontations are increasingly common, and stress is known to make animals' immune systems less effective in many situations. Having the apes living in such small, fragmented areas of forest isn't good either for them or for local people. The chimps can't get enough food in the degraded forest all year round, so when their favoured fruits are out of season they tend to emerge and raid farmers' crops, making off with bananas, sugar cane and other valuable crops.

'It's a bad situation for everyone,' McLennan says. 'People's activities are changing the landscape and affecting the chimps' behaviour - if they can't get enough to eat in the forests, they start looking for food in people's fields. Chimpanzees are big wild animals and can be very dangerous; it's not surprising that local people are afraid of them, so they harass them and try to drive them off. But it turns into a vicious cycle, because it can make the chimps more aggressive.'

McLennan is now planning follow-up research looking in more detail at the health implications of chimps and humans living in close contact for members of both species.

The paper appears in the American Journal of Primatology.

Explore further: Male monkey filmed caring for dying mate (w/ Video)

More information: High Frequency of Leaf Swallowing and its Relationship to Intestinal Parasite Expulsion in "Village" Chimpanzees at Bulindi, Uganda. Matthew R. Mclennan, Michael A. Huffman. American Journal of Primatology, Volume 74, Issue 7, pages 642-650, July 2012. DOI: 10.1002/ajp.22017

Related Stories

Survey: People know much about chimps

Dec 11, 2007

A Humane Society of the United States survey determined that people know more than they thought about chimpanzees, including the fact they are endangered.

Gesturing observed in wild chimpanzees

Mar 22, 2006

It was once thought only humans gestured to direct another person's attention, but such "referential" gesturing has now been observed in wild chimpanzees.

Study: Chimps don't care about friends

Oct 26, 2005

University of California-Los Angeles scientists say helping others is apparently a uniquely human habit -- or, at least, not a habit shared by chimpanzees.

Chimpanzees use sex tools

May 05, 2010

( -- Many animals are known to use tools, but chimpanzees (our closest living relatives) show the most varied and complex use of tools, and the males in one group of chimps have even been observed ...

Recommended for you

Male monkey filmed caring for dying mate (w/ Video)

15 hours ago

( —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Orchid named after UC Riverside researcher

Apr 17, 2014

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

Apr 17, 2014

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

Apr 17, 2014

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

4 / 5 (4) Jun 21, 2012
We need more national parks and reserves. A tourism industry would outperform the agriculture that's pressurising these chimps. Both the local people and the chimps would benefit.
2.3 / 5 (6) Jun 21, 2012
Uganda has one of the highest population growth rates in the world.

-Pressure is not the issue. Extinction is the issue. Until the religionist cultures which maintain this growth rate are destroyed, not only are these animals in danger of disappearing, but the region will remain locked in perpetual conflict.

-They need all the food they can get. Bush meat is a favorite of indigenes. And who would want to vacation in a region full of warlords and starving criminals? Would you like to try somalia? Hotels are cheap I bet.
1 / 5 (3) Jun 22, 2012
I suspect that when these "damned dirty apes" rise to power-- we will be the ones who self-medicate.

More news stories

Researchers successfully clone adult human stem cells

( —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Researchers develop new model of cellular movement

( —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

Plants with dormant seeds give rise to more species

Seeds that sprout as soon as they're planted may be good news for a garden. But wild plants need to be more careful. In the wild, a plant whose seeds sprouted at the first warm spell or rainy day would risk disaster. More ...

Male monkey filmed caring for dying mate (w/ Video)

( —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Impact glass stores biodata for millions of years

( —Bits of plant life encapsulated in molten glass by asteroid and comet impacts millions of years ago give geologists information about climate and life forms on the ancient Earth. Scientists ...