Three kinds of dung beetles have an unusual way of getting around.
A team of scientists who carried out research in South Africa discovered that three species of dung beetles have a “galloping” gait to navigate to their nests. The findings, published in the journal Current Biology, suggests the strange step may be an evolutionary trait.
“This species of Pachysoma grabs bits of poo and gallops forward with it. That is really odd. Most insects walk with a tripod gait,” Professor Marcus Byrne of Wits University said in a statement pointing to how the insects usually plant three legs on the ground while swinging their other three legs forward. “For an insect to abandon the tripod gait and use its legs together in pairs like a galloping horse is really radical.”
Scientists came across the dung beetles – known as Pachysoma endroeydi, P. hippocrates and P. glentoni -- while studying wingless desert dung beetles in South Africa and how they navigated to their burrows.
"We noticed that [one species we were looking at] was kind of bobbing along in a peculiar manner," Dr. Jochen Smolka from the University of Lund in Sweden told BBC News. "At first we thought that maybe there was something wrong with it - that maybe it had some damage to its hind legs. And then we noticed that all of the beetles of that species move like that most of the time."
Using a high-speed camera, the team of researchers captured the beetles’ galloping gait, then carried out lab tests to see how they moved across sandpaper.
The three species belong to the genus Pachysoma – a type of beetle that collects dry feces, hoards it in a nest and shares it in repeated foraging trips rather than transporting one giant ball.
“For most dung beetles, it’s always a one way trip – grab the poo, run away and never go back. The very marked pacing of Pachysoma’s gallop might be giving it a better signal in terms of estimating the return distance from the food to its nest. When it gallops, it slips less in the soft sand,” Byrne said.
While the beetles don’t go airborne, like horses do, their legs move similarly. But unlike mammals, they gallops slowly and usually can’t keep pace with their tripod-walking relatives, New Scientist reports. Smolka suggests the unusual gait is used to help the beetles navigate back to their burrows by stabilizing their heads.
“Dung beetles have two eyes on each side of their head, one on top and one on the bottom, looking at the sand and we think Pachysoma might be registering optic flow with its bottom eye over the sand,” Byrne said explaining how the beetles’ measure how far they’ve traveled from their nests.
And galloping comes at a cost. Unlike other dung beetles, Pachysoma lost their ability to fly.
“There are 800 species of dung beetle in South Africa and most of them fly. To fly makes sense because poo is a very ephemeral resource,” Byrne said. “It’s only useful for a few days and it’s very patchy – you don’t know where you’re going to find the next dropping. That’s why Pachysoma is so weird. Why would anyone give up flying?”
Scientists theorize the insects sealed their wing gases to conserve moisture in the dry desert. “Breathing causes massive water loss. We think they’ve closed the elytra case to create a breathing chamber which keeps moisture inside,” Byrne said.