Beneath North and Central American grasslands, pocket gophers dig labyrinths of winding tunnels hundreds of feet long. Now, researchers have found that the rodent architects may also be farmers, tending to underground roots they harvest for food.
As the gophers construct their large tunnels, they turn over the soil, aerating it in the process, and munch on roots that grow and hang in the tunnels over time, reports Evrim Yazgin for Cosmos. The behavior is not advanced agriculture, but it is a carefully managed food production system that provides the optimal conditions for root growth, Oliver Whang reports for the New York Times. This week, details on the mammal’s root cropping behaviors were published in Current Biology.
Pocket gophers are brown rodents about the size of a Guinea pig. Their diet consists of roots, stems, and some weeds and grasses above ground, reports Science’s Katherine Irving. The gophers spend most of their time underground and only venture to the outside world to forage for food or mate.
To find out how and why the gophers construct large tunnels on their plant-based diets, scientists at the University of Florida dug trenches around three gopher tunnel sections in a Gainesville pasture and placed oil barrels at each trench to keep them out, Science reports. From here, the team photographed the blocked sections and noticed that roots grew and filled the areas, whereas, in the places left open for the gophers to roam, the roots stayed short.
The researchers then calculated the daily root growth to determine how much of the gopher’s energy needs could be met by harvesting the roots, a statement explains. Previously, it was thought that the gophers survived by eating away at roots they encountered while constructing their tunnels. Based on the calculations, the scientists found that the energy needed to dig a tunnel is too much to be supported by the roots that gophers eat while excavating it, but if they eat roots grown in other tunnels that are already dug, they can meet the energy expenditure, reports Sofia Quaglia for National Geographic.
Through building and maintaining the extended networks of tunnels, the gophers create an environment for roots to thrive. The animals also scatter their poop and urine within the tunnels, which fertilize the growing roots, per National Geographic. “They’re providing this perfect environment for roots to grow and fertilizing them with their waste,” says Veronica Selden, a zoologist at the University of Florida and the study’s first author, in a statement. When the potato-sized mammals nibble on the dangling roots, they also encourage growth.
“You’re a small mammal going along, and you encounter a large root, and you bite it off, but it’s not very digestible because it has a lot of lignin or celluloses, it’s tough, it’s hard,” says Francis Putz, an ecologist and study author at the University of Florida, to National Geographic. “But in response to being cropped, that root will make many small roots, and those will be really tasty and more digestible.” By harvesting the root crops, the gophers can supply 21 to 62 percent of their energy needs, making up the rest of the calories needed to continue their burrowing habits.
While some experts argue that the gophers aren't technically farming because they don’t plant, weed or distribute their crops, the researchers involved in this new study think the finding opens up the possibility that other ground-dwelling rodents could have behaviors that qualify as husbandry too.