Dung Beetles Dig Deep Burying Climate Change Literally

Some dung beetles may already possess a survival strategy in the face of global warming. As temperatures rise, temperate rainbow scarabs simply dig deeper. By burying their dung further down, they keep their developing young cool enough to survive. Ecologist Kimberly Sheldon reported these findings Jan. 6 at a meeting of the Society for Integrative and Comparative Biology in Portland, Ore. So, does this behavior actually give them an edge in a warming world?

Greenhouses Reveal Beetle Heat Escape Plan

Preliminary field experiments suggest their tropical cousins lack this behavioral flexibility. This makes the tropical species potentially more vulnerable to climate change. Rainbow scarabs are a type of tunneling dung beetle. Instead of rolling famous gigantic dung balls across the ground, these grape-sized insects dig tunnels. They carry the nutritious material below ground and shape it into a hard ball, laying one egg safely inside. Sheldon, from the University of Tennessee, Knoxville, designed an experiment to test their burrowing habits.

Her team placed miniature “greenhouses” over buckets filled with soil in a field. These plastic cones concentrated the sun’s warmth, raising the ground temperature about 2 degrees Celsius above ambient. Dung beetles under these cones experienced the simulated warmth while still facing normal weather fluctuations through a hole in the cone’s tip. The scientists then compared their behavior to that of dung beetles in buckets without cones. But what exactly did they find the beetles doing?

Dung Beetles Take the Plunge Downward

Sheldon started this particular line of research more than six years ago. An earlier attempt showed that female beetles buried their eggs deeper when under the greenhouses. They moved the brood balls an average of five centimeters deeper, dropping the incubating temperature by about 1 degree. Unfortunately, floods destroyed that study site before she could confirm if this helped the insects survive. Dung beetles can’t catch a break sometimes, even in a scientific study.

In 2023, her team successfully repeated the experiment and got their answers. Despite the artificial heat, just as many young emerged as adults from the deeper dung balls. This success rate matched that of young from shallower burrows in the cooler buckets, she reported at the meeting. This suggests the burrowing behavior is a direct and effective response to higher temperatures. Dung beetles in temperate zones, it seems, have a built-in toolkit for handling heat waves.

Tropical Scarabs Stuck Shallow and Sweating

Other researchers have found that some sweat bees and tree frogs also change their behavior to cope with climate shifts. However, not all animals possess this flexibility, not even close relatives of the rainbow scarab. Sheldon’s team conducted similar experiments in Ecuador with a tropical cousin, *Oxyternon silenus*. These particular dung beetles did not change the depth of their brood balls despite the simulated warming. Do the eggs of the tropical beetles face a higher risk because of this rigidity?

Tropical climates are generally less variable than temperate ones. This stability means there has been little evolutionary pressure for these beetles to develop flexible behaviors. Their inability to simply dig deeper in response to heat is therefore concerning, Sheldon noted. The survival of these tropical dung beetles may depend on other, unknown factors as global temperatures continue to climb. Their fate, unlike their resilient temperate relatives, remains an open question.

Some Beetles Can’t Dig Themselves Out

This research on the two beetle species offers a small but telling glimpse into a much larger problem. For the temperate rainbow scarab, survival means simply working harder and digging deeper. That instinct, honed by a variable climate, now serves as a natural shield. The tropical species, however, has no such shield.

Evolving in a stable world left it without this particular tool for change. The contrast highlights a quiet truth about our current era. Some creatures will adapt and become, in a sense, dung beetles at weathering the storm. Others, through no fault of their own, may find the world has simply gotten too hot, too fast. Their fate remains uncertain, as for them, rising temperatures present a threat they cannot simply burrow away from.

Beetle Fate Hangs in Uncertain Balance Now

Researchers will keep a close eye on these dung beetles, tracking which ones figure things out and which ones fall behind. The truth is, their future hinges on a bunch of stuff scientists are just now starting to wrap their heads around. Just because one group of beetles handles the heat doesn’t mean another group halfway across the world will manage the same trick. That uncertainty leaves their long-term survival feeling like a total toss-up.