Pocket gophers certainly don’t qualify as card-carrying 4-H members, but rodents could grow roots in the open from their moist, nutrient-rich tunnels.
Ground squirrels feed mainly on roots encountered in tunnels dug by rodents. But local terrain doesn’t always provide enough roots to support ground squirrels, two researchers report in the July 11 Current biology. To make up for the shortfall, gophers practice a simple type of agriculture by creating conditions more conducive to root growth, suggest ecologist Jack Putz of the University of Florida at Gainesville and his former zoology student Veronica Selden.
But some scientists believe that it is an exaggeration to call agricultural activity rodents. According to these researchers, ground squirrels do not actively till the soil, but inadvertently alter the environment when rodents eat and poop, as all animals do.
Digging a tunnel requires a lot of energy – up to 3,400 times more than walking along the surface for ground squirrels. To see how the creatures got all that energy, Selden and Putz in 2021 began investigating the Southeast Pocket Waffle Tunnels (Geomys pintis) in an area being restored in longleaf pine savannah in Florida that Putz partly owns.
The duo took root samples from the soil adjacent to 12 gopher tunnels and extrapolated the amount of root mass a gopher would encounter when digging one meter of tunnel. Then the researchers calculated how much energy these roots would provide.
“We were able to compare the cost of energy versus the gain, and found that on average there is a deficit, with about half of the cost of digging not taken into account,” says Selden.
Examining some of the tunnels, Selden and Putz saw gopher droppings strewn inside with signs of small pitting pulled out from the roots and churning of the soil.
Ground squirrels, the researchers conclude, provide conditions that promote root growth by spreading their own waste as fertilizer, aerating the soil and repeatedly nibbling on roots to encourage new growth.
“All of these activities encourage root growth, and once the roots grow through the tunnels, the ground squirrels harvest the roots,” Selden explains. She and Putz say it amounts to a rudimentary form of farming. If so, ground squirrels would be the first non-human mammals to be recognized as farmers, Putz says. Other organisms, such as certain insects, also grow food and began doing so much earlier than humans (SN: 04/23/20).
But the study has its skeptics. “I don’t really think you can call it farming by the human definition. All herbivores eat plants and everyone poops,” says JT Pynne, a wildlife biologist at the Georgia Wildlife Federation in Covington who studies southeast pocket gophers. So root nibbling and tunnel droppings may not be signs of farming, just gophers doing what all animals do.
Evolutionary biologist Ulrich Mueller agrees. “If we accept the tenuous evidence presented in Selden’s paper as evidence for agriculture…then most mammals and most birds are farmers because each of them incidentally also has beneficial effects on certain plants that these mammals or birds also feed on,” he says. .
Not only that, but the study is also dangerous, says Mueller, of the University of Texas at Austin. Audiences will see through “the shallowness of the data,” he says, and conclude that science is “just a bunch of stories, eroding general trust in science.”
For her part, Selden says she understands that because gophers don’t plant their crops, not everyone is comfortable calling them farmers. Yet she argues that “what qualifies ground squirrels as farmers and distinguishes them from, say, livestock, which incidentally fertilizes the grass they eat with their waste, is that ground squirrels cultivate and maintain this ideal environment. for root growth.
At the very least, says Putz, he hopes their research will make people kinder to rodents. “If you go on the web and put on a ‘pocket gopher,’ you’ll see more ways to kill them than you can count.”