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Somewhere near you, an animal is defecating.
In fact, each day, the animal kingdom produces roughly enough dung
to match the volume of water pouring over the Victoria Falls.
So why isn't the planet covered in the stuff?
You can thank the humble dung beetle for eating up the excess.
Capable of burying 250 times their body weight in a single night,
these valiant insects make quick work of an endless stream of feces.
Over 7,000 known species of dung beetle run clean-up duty across six continents
—everywhere except Antarctica.
A dung beetle's first task is to locate dung.
Some live on the anal regions of larger animals,
ready to leap off when they defecate.
Others sniff out feces that animals leave behind.
A pile of elephant dung can attract 4,000 beetles in 15 minutes.
So once a beetle finds dung,
it must work quickly to secure some of the bounty for itself.
Most dung beetle species fall into one of three main groups:
rollers,
tunelers,
and dwellers.
Dung rollers sculpt a ball of dung, and using their back legs,
quickly roll it away from competitors.
Potential partners jump on the ball,
and once the ball-maker has selected their mate,
the pair dig their dung ball into the soil.
Once it's been buried, the female lays a single egg within the dung ball.
Tunnelers have a different approach.
Digging underneath a pat, some drag dung down into the soil
and pack it into clumps known as brood balls,
dung balls,
or dung“sausages,”depending on their shape and size.
Male tunnelers sport a spectacular array of horns
to fight each other for control of these tunnels,
which they then defend until the female's laid her egg.
Some male tunnelers avoid the fray by masquerading as hornless females
and sneaking into tunnels to mate while the guardians' heads are turned.
The third group of dung beetles, dwellers,
take the most straightforward approach,
laying their eggs directly into a dung pat.
This makes their offspring more vulnerable to predation
than those of the tunnelers and rollers.
As the larvae feed, they riddle the dung pat with tunnels,
leaving remains that are quickly colonized by bacteria and fungi and weathered away.
Inside a tunnel, ball, or pat, once the larvae hatch,
they consume the dung before metamorphosing into a pupa
and then an adult beetle.
Besides clearing dung, the actions of these beetles
have considerable ecological importance.
For one, they serve as secondary seed dispersers.
Dung from monkeys,
wild pigs,
and other animals is riddled with seeds from the fruits they eat.
When beetles bury their dung balls,
they inadvertently protect these seeds from predators
and increase the likelihood they'll germinate.
The advantage is so great that one South African plant
has evolved to produce seeds that look and smell like dung
to trick beetles into burying them.
Dung beetles also play important roles in agricultural systems.
Livestock, like cows and sheep, produce huge amounts of dung,
which contains nutrients that can benefit plants.
The beetles break up the dung and tunnel it deep into the soil,
bringing the nutrients into close contact with plant roots.
Their services to farmers have been valued at $380 million a year in the US
and £367 million a year in the UK.
Dung beetles can even help us battle global warming
by reducing greenhouse gas emissions associated with farming.
Microbes living in oxygen-poor livestock dung
produce methane, a potent greenhouse gas.
But beetles oxygenate pats when they tunnel into them,
preventing the microbes from producing methane.
The dung beetle spreads seeds,
helps farmers,
and fights climate change
—and accomplishes it all simply by doing its business.
Maybe next time you come across some dung in the forest or a field,
you'll be tempted to take a closer look.
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Why isn't the world covered in poop? - Eleanor Slade and Paul Manning

5680 Folder Collection
April Lu published on April 13, 2018   April Lu translated   Evangeline Chung reviewed
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