Why isn't the world covered in poop? - Eleanor Slade and Paul Manning

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Each day, the animal kingdom produces roughly enough poop to match the volume of water pouring over Victoria Falls. So why isn’t the planet covered in the stuff? You can thank the humble dung beetle for eating up the excess. Eleanor Slade and Paul Manning explain how these valiant insects make quick work of an endless stream of feces.

Lesson by Eleanor Slade and Paul Manning, animation by Anton Bogaty.

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,

tunnelers,

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.