Radar has been put to use to reveal the layout of wombat tunnels. The technology could prove useful in protecting the charismatic marsupials, and has potential for helping us understand other subterranean species. Already, it has raised interesting questions as to how geological conditions can shape the social behavior of burrowing creatures.

Michael Swinbourne is a Ph.D. student at Adelaide University studying southern hairy-nosed wombats. While immensely popular with tourists, wombats are less beloved by farmers, many of whom apply for licenses to kill them to prevent damage to agricultural infrastructure. Government agencies want to know wombat numbers before approving such permits, but Swinbourne told IFLScience that existing methods for counting wombats are very inadequate.

“They're nocturnal and they live underground,” Swinbourne explained. “Currently people use a formula that each wombat equals so many holes, but that doesn't take into account soil type.” Since the ratio of holes to wombats varies with soils, calculations that use an unvarying formula can drastically misrepresent the number of wombats. This can push populations to local extinction if culling permits are granted based on badly estimated numbers. 

To know what is really going on, we need to see inside the burrow, but past assessments of wombat burrows have relied on digging up the burrow, which is slow, expensive, harmful to the inhabitants and, as Swinbourne noted to IFLScience, “prevents us going back months later and seeing what has changed.”

Swinbourne turned to ground-penetrating radar. In Wildlife Research, Swinbourne reported that “Wombat warrens, which are networks of interconnected burrows, are readily detectable from space,” with holes counted using Google Earth. He, however, used a hand-operated device with his feet firmly on the ground to examine how geology changes burrows of the southern hairy-nosed wombat.

^{Michael Swinbourne's colleague, Mike Hatch, using the ground-penetrating radar device. University of Adelaide}

The technology Swinbourne used has been available to scientists for two decades, but he told IFLScience, “It has been used very sparingly, only 4-5 times in that period, initially on rabbits and more recently gophers.” Previous researchers were primarily testing if the radar worked for mapping burrows, but to Swinbourne's surprise, once proven effective it was largely abandoned despite the wide array of applicable species. It is, however, popular for archaeologists seeking buried human constructions.

Much of the southern hairy-nosed wombat's range is over limestone, sometimes deep enough to house huge caverns, but often just a few centimeters thick. “Wombats love this [limestone],” Swinbourne told IFLScience. “It's a very stable roof.” Consequently, wombats in these areas build complex warrens of tunnels and chambers that resemble rabbit burrows or ant nests. Swinbourne called one the “London underground of wombat burrows.” Elsewhere, holes usually lead to a single tunnel.

The need for such elaborate mansions is unclear, but a chance observation of Swinbourne's suggests it may be because these warrens have more than one occupant. “I stuck my head down one and there were three wombats living close together. I don't know who was more scared, me or the wombats,” Swinbourne told IFLScience.

Swinbourne didn't stick around to see if the wombats were all adults, but said they were at least adolescent in age, and the discovery has changed thoughts about how wombats, previously thought of as highly solitary creatures, live. “They might be more sociable than we thought,” he said in a statement.

^{Swinbourne is the husband of Alcye Swinbourne, whose Ph.D. in wombat tickling has previously featured on IFLScience. University of Adelaide.}