Eating dirt in the Amazon

By Gaia Vince 14 October 2010
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‘Eating dirt’ is not just an insult – it’s a real behaviour observed in humans, and animals too.

GEOPHAGY, IT’S CALLED, the practice of eating dirt. Turns out that ‘eating dirt’ is not a metaphor for humiliation, but a recognised activity with a nice technical name. In fact, people have been eating clay, chalk and mud for millennia around the world to neutralise food toxins, aid digestion (think: Pepto-Bismol and kaolin) and supplement nutrients during pregnancy.

Animals, too, eat dirt. Scientists have recorded everything from butterflies and birds, to monkeys and elephants congregating at specific sites to munch on the earth, getting valuable minerals including calcium and sodium.

For wildlife lovers, these sites represent a great opportunity to view the visiting fauna – and Manu, in eastern Peru, the most biologically intact and undisturbed part of the Amazon rainforest, has a few clay licks we’re eager to see. Animals from bush dogs to peccaries and frogs have been observed using the licks here.

Amazing Manu

We head into Manu national park in a canoe that requires heaving over the riverbed every now and again due to the low water level. The rainforest here is home to a dazzling biodiversity, including at least 1800 different bird species (more than any other protected area on Earth – there are only about 10,000 bird species worldwide), 13 primate species, 400 ant species and various indigenous human tribes, including 100s of ‘uncontacted’ people, who choose to live a hunter-gatherer existence without the cultural and disease-carrying influence of more recent forest colonisers.

“Manu is one of the very few parts of the Amazon that was protected before it was impacted by hunting and logging – it’s one of the last places that you can see mahogany trees standing tall,” says British-born ornithologist Barry Walker of the Manu Wildlife Centre, who’s lived in the area and studied its birds for more than 20 years. “But the Hunt Oil, Houston, concession is a serious threat.” Hunt Oil is exploring for oil and gas at the edge of the park.

A tapir enjoying the clay licks of Manu Wildlife Park in Peru

Clay licking

It was researchers at Manu Wildlife Centre who first made detailed reports of tapirs using the clay licks, as well as the first reported sightings of black spider monkeys eating clay. Now, researchers are discovering geophagy in more and more primates, indeed it may be that it is the rule rather than the exception to eat dirt.

In early morning, we head along the upper Madre de Dios river where there is a high bank of clay visited by hundreds of squawking macaws and parrots. It’s an impressive sight: a blast of colour and sound, with my favourite being the scarlet macaws. These monogamous birds arrive in pairs or in threes (son or daughter in tow) to the lick, where they hang on to the wall and seem to manage to eat and shout at the same time.

It’s an important social and mating spot for the birds – those chaperoned youngsters will likely find a partner for life at the clay wall, and this is breeding season.

Downstream, on the greater Manu river, we surprise a group of bright red Bolivian howler monkeys, lounging on the bank, eating the clay with audible scoffing. This is the peak season for clay-eating, Walker explains, because in mid-winter (well into the dry season), tasty, easily digestible fruits and berries are hard to find. The animals are forced to eat more of the toxin-loaded leaves and fibrous fruits that are hard to digest. Clay minerals seem to help that process. In birds, the grit may provide extra help in the gizzard; in mammals, it’s likely that the minerals and alkaloids help make the plant nutrients more bioavailable.

Tapirs licking at the door

The biggest treat is reserved for the Manu Wildlife Centre itself, though, where there is a mammals clay lick. The lick is most active at night, which means leaving our cosy, bug-free cabins for an hour-long trek into the forest to a specially built hide. It is perfectly located just metres from the clay lick and as night falls, we make ourselves comfortable. Only problem is it’s a little too comfy. Walker has placed mattresses and pillows under the mosquito nets and it’s not long before there’s a loud, tapir-scaring snoring from our designated photographer. I nudge Nick awake, and we try to concentrate on singling out tapir noises from the sirens of cicadas, rumble and croaks of frogs, swishing of bats and, I’m sure, roaring of nearby jaguars.

Eventually, there’s a rustle in the forest and in the thin torchlight we see not one, but two tapirs – a mother and baby. They chomp away at the clay for perhaps 20 minutes, twitching their noses and huffeting around like hippos. It’s magical, and when they eventually leave, we stay another couple of hours hoping for a revisit.

Walking back in the blackness, trying to avoid sci-fi movie calibre beasties and not step on bullet ants, army ants, scorpions, etc, we marvel at our sighting. Tapirs, the South American indigenous horse, travel miles to visit a clay lick. Will they still come, we wonder, if the area is invaded by oil companies and those who follow the soon to be completed Interoceanic highway between Brazil and Peru, such as loggers, animal poachers and hunters? (In Brazil, a 50-metre-wide halo of deforestation follows roads into the Amazon, according to 2008 research.)

Gaia Vince is an Australian journalist who
is travelling around the world reporting on the effects of climate change and
sending regular dispatches to
Australian Geographic. She writes
for the
BBC, New Scientist and The
Guardian. Find her blog at

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Manu Wildlife Centre