Humans aren’t the only farmers in the animal kingdom.
Pocket gophers live underground, creating and inhabiting an elaborate tunnel system. But while they’re making and moving through this subterranean labyrinth, they are also tending fields of roots. Researchers who have studied the animals say that makes the rodents the only non-human mammal that farms for a living.
“Pocket gophers are little understood and much maligned. A search on the internet, for example, will yield dozens of ways to kill them,” study author Francis Putz, a biology professor at the University of Florida, tells Treehugger.
“We were intrigued by the question of how they could possibly obtain enough root food from digging, given the energetic costs of that activity. We also wondered why they invest so much in keeping extensive systems of tunnels open.”
In order to study what was happening with the Southeastern pocket gopher (Geomys pinetis), Putz teamed up with Veronica Selden, who was an undergraduate student at the time and recently graduated with a degree in zoology. They picked up shovels and went digging on Putz’s property.
They created dams of sheets of metal, attempting to block the gophers from their tunnels so they could measure the roots that were growing in the underground system. They did this, mostly unsuccessfully, for months, as the ingenious rodents found ways around the blocks to get to the roots.
“Working belowground is always a challenge,” Putz says. “For this project, we shoveled dozens of cubic meters of soil in our efforts to find and then isolate sections of tunnels. Our initial efforts failed because the gophers circumvented the blockades we established and refilled the tunnels in which we hoped to measure root ingrowth.”
The researchers were able to come up with a solution. They cut off the ends of 50-gallon drums, then placed a drum open-side down into the soil, surrounding an area of tunnels. Their shape kept the gophers from entering the study area on any side, while still allowing the plants to grow.
“It was only when we adopted the cut barrel technique that we successfully isolated sections of tunnel into which root growth was prolific,” Putz says.
Farming for Energy
First, researchers calculated the daily amount of root growth. Then they were able to determine what portion of the animals’ energy needs were met by harvesting the root crops.
They found the roots they eat while excavating don’t make up for the great deal of energy gophers spend when they are digging their tunnels. However, harvesting and eating the roots that grow in the tunnels they’ve already created may help them get enough energy to keep digging tunnels in order to find more food.
The results were published in the journal Current Biology.
Other animals are known to farm. For example, some species of ants cultivate gardens of fungus. They fertilize the fungus and protect it from pests and mold.
Gophers farm, but they don’t fertilize or weed their crops. And researchers note that the definition of farming is open to interpretation.
Farming is “the activity of growing crops,” Putz says. “Many people focus on the cultivation of annual crops in seasonal environments, but in less seasonal tropical environments, farming is based on the management of perennials and need not involve seed planting. In this traditional form of permaculture, farmers often subtly manage trees, lianas (woody vines), shrubs, and other perennial plants so that they yield the desired products such as starch from the stems of Metroxylon palms as well as edible leaves and fruits from innumerable species.”
In the case of pocket gophers, they provide the fields (their tunnels) where roots thrive due to fertilization with gopher waste and soil aeration.
Inconvenience for Science’s Sake
The researchers acknowledge in their paper that “gophers were inconvenienced by this research but none were injured.”
Putz explains why he finds the rodents so fascinating.
“While gopher mounds are common as dirt, few people have had the pleasure of seeing one of the animals,” he says. “Learning about them, especially that they are farming roots, will hopefully increase respect for these fossorial beasts.”
And learning about them can also help protect them, he points out.
“Due to the challenges of working underground, discoveries like ours await folks with shovels, strong backs, and curiosity,” Putz says. “We also hope that increased understanding of pocket gophers will contribute to their conservation.”
