How do dung beetles like their dung? Stinky, and from omnivores like us, a new study says.
Scientists already know a lot about the excrement-eating insects’ preference for dung types and conditions. But a University of Nebraska team got curious about what dung beetles in North America‘s Great Plains would do with waste from more exotic animals, such as zebra, waterbuck, or moose. These species live on game farms in the region.
Dung and carrion beetles feed on a rotten rat. Photograph courtesy W. Wyatt Hoback.
For their experiment, Sean D. Whipple and co-author W. Wyatt Hoback, of the University of Nebraska at Kearney, baited pitfall traps with various types of poop, including native and exotic carnivores, herbivores, and omnivores. Some of the traps also contained carrion. Over two years, the traps captured 9,089 dung beetles from 15 different species, allowing the scientists to record which dung was most attractive.
Ominvore dung—specifically from people and chimpanzees—was overall the beetles’ favorite feces, most likely because omnivore dung “tends to be more odiferous,” said Whipple, a postdoctoral research associate at the University of Nebraska-Lincoln. Chimp dung, he added, is “absolutely disgusting.”
A species of dung roller in the genus Melanocanthon. Photograph courtesy Marlin E. Rice.
To the scientists’ surprise, Nebraskan dung beetles preferred exotic-animal dung over dung from native species. Also intriguing was that closely related species of beetle seemed to have differing preferences for carrion and dung, Whipple said. It may be that the beetles are “segregating out their behavior”—in other words, avoiding competition with each other.
During their field research, Whipple and Hoback would also sometimes encounter other species that had been drawn to the dung. “It’s always interesting when you flip open the lid [of the trap] and a rattlesnake is there,” Whipple said.
Overall, dung beetles are often misunderstood, added Whipple, whose study appeared recently in the journal Environmental Entomology.
“People think of dung beetles as the ones rolling the balls in Africa,” he said. “One of the common questions I get is, We have those here? Nebraska has about 50 species,” he said.
Two male rainbow scarabs (Phanaeus vindex). Photograph courtesy W. Wyatt Hoback.
What’s more, dung beetles aren’t just dung rollers—they’re also dung tunnelers and dwellers. Rollers shape pieces of dung into balls and roll them away from the pile. They bury their ball to either munch on later or to use as a place to lay their eggs. Tunnelers bury their dung treasure by tunneling underneath the pile. And dwellers actually live inside dung piles, according to National Geographic Kids.
Dung beetles range from about a millimeter in length “all the way up to the big guys,” Whipple said, which can be more than two inches (five centimeters) long. The insects live in a variety of habitats, from deserts to forests, and can sport horns or a brilliant iridescence, as seen above.
(Read another Weird & Wild post on why dung beetles dance.)
Whipple also noted that the insects perform a crucial “ecosystem service”—science speak for helping the environment stay healthy. That’s because dung beetles process a lot of poop that would otherwise pile up. In parts of Texas, for instance, the insects bury about 80 percent of cattle dung, according to Arizona State University.
As they say, it’s a dirty job—but someone’s got to do it.
Check out more weird coverage on National Geographic News.