For many, it's a subject and object to be avoided. We're talking poo. Faeces, excrement, or any of the euphemisms used to describe a substance that, in reality, is fundamentally important to life.
But rather than avoid it, BBC Earth can reveal how astonishingly versatile it really is. Here's five surprising and important uses of poo.
Scientists have created a museum of poop
Yup – it’s true. Scientists at the Isle of Wight Zoo in the UK have erected a poo shrine, allowing zoo-goers to get up close and personal with 20 individually encapsulated stools. The poos come from various animals: there are samples from the zoo’s lions, as well as from meerkats, skunks – there’s even human baby poo.
“They all vary in size and shape and texture and detail – it continues to be an extraordinary unfolding of information,” says the museum’s curator Nigel George.
While none of the team members are scatologists, George says even a layperson can tell a lot about an animal by examining a sample of its faeces.
Poo continues to be an extraordinary unfolding of information
They show what animals are eating – crow poo, for instance, generally contains quite a lot of bones or beetle wing cases in it. “The carnivore poos tend to be a lot smellier than the herbivore ones,” he adds.
One herring gull bird sample had remnants of plastic in it, showing how there is now a human impact on animal poo.
With an average poo containing about 75% water, the team have learnt by trial and error how to encapsulate the turds to “make them less smelly and safe for the public to look at”.
To do this they spent a year inventing a poo-drying machine.
“It’s simple but it does the job,” says George.
He describes the machine as a long pipe with ‘poo hammocks’ that go into a poo dryer. Depending on the size of the faeces it will stay in the dryer for anything from a day to a couple of weeks. It’s then covered in resin and encapsulated, with vacuum chambers used to remove the air bubbles.
The end result looks a little like a crystal ball. Except it has a poo in the centre.
“When you see them on their little podiums, I don’t think anyone has any idea how much effort has gone into making it,” says George.
The end result looks a little like a crystal ball. Except it has a poo in the centre
He says the public’s reaction has taken them by surprise: “What we’ve noticed is that people’s initial reactions aren’t what they think they [would] have. The disgust instantly evaporates and people are there with their noses pressed against the samples, wanting to see what’s inside.”
George says the concept has gone global since the museum opened in March. “Clearly everyone wants to talk about poo.”
Whale poop makes the world’s nutrients go round
While most marine animals eat close to the water’s surface and poo in the deeper waters, whales do the opposite. It’s this, Joe Roman says, that makes all the difference.
“When whales come up to the surface, right before their last dive, they do a big dump,” says Roman, a biologist at the University of Vermont, US.
This faecal plume, as it’s known, is rich in nutrients, depositing vast quantities of nitrogen, iron and phosphorus at the water’s surface.
When whales come up to the surface, right before their last dive, they do a big dump
“So they can fertilise the ocean,” says Roman. “[They] bring the nutrients back to the surface.”
The effect is known as the whale pump – and it’s something that Roman has spent the past 10 years studying.
Once the nutrients are at the water’s surface, fish such as salmon can consume them. These fish are then in turn eaten by seabirds who transport the nutrients from the sea to their breeding colonies onshore, where they are subsequently eaten by land animals such as bears. In this sense, Roman says “whales play a part in bringing [the world’s nutrients] from the bottom of the ecosystem to land”.
He and his colleagues have even tracked how nutrient movement around the world has evolved through Earth’s long history.
Until about 60 million years ago, there were no whales. It was around that time that one group of land mammals began dipping their toes into rivers, eventually becoming fully aquatic and colonising the ocean as whales and dolphins. The whales started feeding on fish and crustaceans and so evolved the ability to break down chitin – a component of the hard shell or exoskeleton that surrounds some shellfish.
“Most mammals can’t break this down. It’s meant that the microbial community of whales is completely different from what we realised,” he says.
The makeup of whale faeces depends a lot on the individual whale responsible, and its diet, says Roman. If the whale feeds on krill, its poo tends to be in the form of red or pink logs about the size of a fist. But if they’re feeding on fish, it’s diffuse and a dark green, about the size of a research vessel, he says.
“It’s an immediate injection of nutrients. Both have the same impact but in different ways.”
Some animals eat poo – and despite this, they can be surprisingly clever
While most of us think of dung as an unwanted waste product that’s evacuated from the body, for some animals it’s a precious resource worth consuming.
“Dung feeding animals are living on the last bit of nutrients that the original eater couldn’t get out of the food,” says Marcus Byrne of Witwatersrand University in Johannesburg, South Africa. “It’s really the knife edge.”
Byrne first began studying poo-eating animals – which include dung beetles, fly larvae maggots and even the delicate butterfly – in Australia in the 1980s.
Dung feeding animals are living on the last bit of nutrients that the original eater couldn’t get out of the food
“There were already 300 [species of] dung beetle in Australia but they were adapted to eating roo poo and not cow poo,” he says. Cow poo is 80% water and comes out in large, sloppy dollops, whereas kangaroo poo is generally more like little, firm pellets.
“Australian dung beetles weren’t adapted to this different dung type,” he says – so it made sense to bring in beetles that had evolved to handle cowpats to deal with the dung produced on Australia’s cattle ranches. It was a very important biocontrol programme that went for some 20 years, he says.
Despite having a brain the size of a grain of rice, dung beetles have some pretty impressive talents, says Byrne, They mould the poo they harvest into spherical balls and then roll it away from the competition.
He says the way they procreate and fight over mates is remarkably developed given their small size. Males advertise their fitness through massive horns on their heads, he says. “They’re tiny animals but they fight for females like they’re antelope, deer or caribou.”
There’s this stupid little animal that’s basically looking at the edge of our galaxy
The small males of the species have also evolved to have larger testes than the bigger beetles.
Apart from being sexual stallions and impressive poo-ball rollers, what really sets the dung beetles apart is their navigation skills.
“They look at the sky and use signals to orientate and navigate themselves,” says Byrne. While we humans are map navigators, the beetles can perceive things we can’t see such as polarised light, colour gradient and intensity gradient.
Byrne showed that one species even uses the Milky Way as a celestial compass to orientate itself, allowing the beetles to shift their poo balls by night.
“It’s romantic and impressive. There’s this stupid little animal that’s basically looking at the edge of our galaxy,” he says.
Ancient horse poo might explain ancient history
For those who don’t know their ancient history (ahem, this author), Hannibal was the leader of the North African Carthaginian army during a war with Rome, which lasted from 218 to 201BC. Hannibal is generally considered one of the greatest military commanders in history, and archaeologists have painstakingly attempted to piece together his movements during this 16-year conflict.
One part though – where Hannibal crossed the Alps with his army and 15,000 horses (and several war elephants) – has remained an enigma. Some have suggested this crossing from modern-day France into Italy was at a pass called the Col de Traversette, 3000m above sea level.
If you’ve got 15,000 to 20,000 horses in the one place for two days, you’re going to have some sort of residue
“There was a lot of circumstantial evidence that this was the route but no one has ever come up with something that’s scientific evidence in that it can be tested,” says Chris Allen, an environmental microbiologist at Queen’s University, Belfast, UK.
The mystery has been debated for the past two millennia by historians, statesmen, academics and even by Napoleon. It might soon be solved thanks to a whole heap of ancient horse droppings.
“If you’ve got 15,000 to 20,000 horses in the one place for two days, you know you’re going to have some sort of residue,” says Allen, who has been labelled a ‘dung boffin’ by his local press.
Partnering with archaeologists, Allen and his team found a hole the size of a football pitch not far from the Col de Traversette. Using genetic analysis and environmental chemistry, the team managed to unearth a mass deposition of animal faeces.
They took soil samples at 5cm intervals to a depth of 70cm, which took them through soil horizons that would have formed 2,200 years ago during Hannibal’s life.
“This churned up layer shows something very physical and distinct happened about 2,180 years ago,” he says. “It suddenly becomes very physically disturbed.”
The disturbed layer was rich in ancient horse dung, which the team could carbon date to about 200BC – very close to 218BC, which is when Hannibal is thought to have crossed the Alps. The soil sample was also really high in Clostridia bacteria, a microbe commonly found in the stools of horses.
“Twelve percent of soil samples had this Clostridia and its bang on the dates that it’s expected. There is a six-fold increase at the correct date,” says Allen, equating the findings to a ‘genetic time capsule’.
2,200 years ago a very large number of mammals went through this place and they left something behind
These observations, along with a number of others, create a “fairly convincing story that 2,200 years ago a very large number of mammals went through this place and they left something behind”.
So far faecal matter has not featured much in archaeology, says Allen. If more archaeologists team up with dung boffins, who knows what they might discover…
Poo-sniffing dogs can save endangered animals
From the old bloodhound chasing the criminal, to airport sniffer dogs – pooches have shown themselves to be extremely good at smelling out most things.
“You couldn’t build a sniffing machine as good as dogs,” says Robert John Young, a wildlife biologist at the University of Salford, UK. And even if you could, “it won’t be able to run around a complex 3D environment like dogs can very quickly. Plus they’re cheap and obedient.
It’s these attributes that mean some poor pups are being trained to chase the smell of poo. It’s helping conservationists track down turds in the wild, so they can know where the animals living. It also helps them learn what the animals are eating.
You couldn’t build a sniffing machine as good as dogs
“It’s not the dog’s breed that’s important but their disposition,” says Samantha Bremner-Harrison from Nottingham Trent University, UK. Bremner-Harrison says pound dogs are often best as they’re high energy and very responsive to rewards.
She has worked with breeders in California, training the dogs to sniff out the stools. She’s now starting up a similar centre in Nottingham.
“The big issue with wildlife is often we want to find faeces because from faeces we can get lots of biological information,” says Young – who keeps poo samples from Brazilian monkeys in his fridge.
When Young began his career 25 years ago, students’ sifted poo under microscopes to find out what animals had been eating.
From faeces we can get lots of biological information
“Now with the new tests and online genetic tools we can get so much more out of it.”
Measuring hormone levels in poo is an effective way to assess an animal’s stress levels (for example, to see how stressed they are by ecotourism) and its sex hormones (to work out when females are ovulating).
This is being done to boost numbers of the Northern Muriqui Monkey - one of the most endangered primates in South America, says Young.
Scientists can also use the stool samples to sequence the animal’s DNA.
By smearing the poo on a special form of filter paper used in DNA analysis, we can see if two groups of gorillas separated by a mountain range are genetically connected, says Young. Amongst promiscuous species, we can see who’s fathering the offspring and what genes individuals have.
“Give me a bit of a monkey poo and I can tell you if a monkey is colour-blind or not,” says Young.
There are a whole host of ways that people have been using faeces to manipulate behaviour to benefit conservation.
For example, ecologists from San Diego Zoo in the US wanted to translocate black rhinoceros in South Africa to areas of lower poaching. Making those sorts of moves is difficult though: rhinos are very territorial and so introducing new individuals into another rhino’s territory can result in attacks.
Give me a bit of a monkey poo and I can tell you if a monkey is colour-blind or not
With the knowledge that rhinos mark their territories with faeces, conservationists can lay the ground for new arrivals. They can take stool samples from the rhinos to be introduced and use them to artificially mark out a territory in the new habitat. Then, when the rhinos are actually introduced to the area a few weeks later, the local rhinos have already become familiar with them. “Then a few weeks later, the rhinos were like – oh, that’s Fred, we know him,” says Young.
Poo is, obviously, a waste product. But for science – and many animals – faeces are anything but useless. That’s something to bear in mind the next time you flush the toilet.
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