♪ ♪ Narrator: In the rolling hills of Hluhluwe Imfolozi Game Reserve, Africa's most beloved mammals feed on the grassy slopes.

And all that eating leads to one thing.

Poop.

In a single day, one elephant alone will drop 300 pounds of it.

[Files buzzing] [Man speaking local language] ♪ Narrator: Dr. Gimo Daniel is on a hunt for some of nature's most unappreciated workers.

A biologist from neighboring Mozambique, he has spent 6 years researching the tiny custodians of South Africa's wild landscapes.

With insect populations declining around the globe, Gimo wants to discover how many species of dung beetle are cleaning up after the park's big game.

[Gimo Speaking English] And I use this bucket to put the balls that they're making.

Narrator: To draw in as many beetles as possible, Gimo and his assistant Vinicius work with a special bait, one only a beetle could love.

[Speaking English]] [Speaking local language] [Speaking English] ♪ Narrator: While a ranger keeps watch for curious lions or buffalo, Gimo and Vinicius dig a series of ground traps.

[Speaking English] ♪ Narrator: They'll wait a full day before coming back to see what species they've caught.

[Gimo speaking English] ♪ Narrator: There are at least 5,000 species of dung beetles in the world, but they all fall into 3 main groups: Dwellers, who live in the dung; tunnelers, who bury straight down beneath it; and rollers, who carve out a ball and quickly haul it away to their nest.

♪ And they're all competing for a resource that most other animals would rather avoid.

♪ From the moment a fresh pile hits the ground, beetles catch the scent and race to claim the hot commodity.

Man: A lot of herbivores partially digest the plant matter that they're eating, and they introduce an enriched soup of bacteria into this plant matter.

And that's a pretty good nutrient-rich resource.

And beetles take advantage of that.

♪ Man: One reason why these dung beetles are adapted to finding this dung so rapidly is that there might be intense competition for a limited amount of dung.

And beetles have evolved different ways of fighting and competing for this limited resource.

Narrator: Dung beetles are considered the strongest insects in the world, building balls up to 30 times their own size.

But some clever beetles save their energy.

They wait for others to do the hard work and try to hijack someone else's ball for themselves.

♪ Other species will present their prize to a possible mate.

♪ Woman: Once a female spots this nice ball of dung that this male has, she'll hitch a ride.

And now she's conserving her energy to save for laying her eggs, the male will push the ball backwards without looking where he's going.

♪ Narrator: With his partner on board, the male pushes the ball as quickly as he can, and he does it upside down.

Sylvana: They use their back legs and push off with their front legs, so they're walking backwards, kind of like a handstand.

And when they're pushing that ball of dung, they can't really see where they're going.

So in order to reorient themselves, they'll climb on top and be able to see where the sun is and be able to orient themselves based on the position of the sun.

♪ Narrator: When the new couple has reached the nesting site, the beetles bury their stash.

The female will lay a single egg inside the ball, which will feed the larva for a month until it transforms into an adult to start the cycle again.

♪ One dung beetle can bury 250 times its body weight in a single day, and in the process they churn and restore the soil.

Gavin: When you're burying dung, you're injecting nutrients into the soil and you're aerating the soil.

So it goes beyond just dealing with waste that no one else wants to deal with.

It's providing nutrients to plants and fungus and bacteria, all of which are important for maintaining a healthy ecosystem.

Narrator: Each species burrows at their own preferred depth from 3 inches to 3 feet below the surface.

The diversity of beetles ensures every layer of the soil is refreshed and fertilized.

♪ Sylvana: Dung beetles are very important for these ecosystems because they're continuing this nutrient cycling, which will help the savanna and help the grasslands grow better grass for the mammals that are eating the grass.

And so it's the circle of life, just with poop.

♪ Narrator: It's been 24 hours, and Gimo and Vinicius head back to the traps to see what the pig dung has brought in.

Wow, that's nice.

[Speaking English] ♪ Narrator: Across South Africa alone, there are at least 800 species of dung beetle.

This tells Gimo there's more to be found in the park than what they're seeing in the traps.

And some species might not be fond of pig poop, which means you'll have to think like a beetle and sniff out some fresh dung.

[Speaking local language] ♪ [Gimo speaking English] Ooh!

Look at this one.

♪ Narrator: Most dung beetles are not picky eaters, but some have become so specialized that they're now highly vulnerable, like one species, anonychonitis, that depend solely on the waste of a single animal-- rhinoceros.

[Gimo speaking English]