Does this gopher ‘farm’ the roots it eats?

Months before making a ground-breaking pocket gopher discovery, Veronica Selden arrived at a grassy pasture in Gainesville, Florida, with two shovels, three oil barrels, and a question: Why were these small animals building such big tunnels? The answer, according to a new study, is that the gophers graze on roots that grow into their tunnels, in what Selden and others say could be the first example of nonhuman mammals doing a kind of farming.

Other scientists say real agriculture involves much more. But, “This paper could spark a lot of future research,” said Stan Braude, a mammal biologist at Washington University in St. Louis. “It’s cool that [it’s] pushing us to look for more examples of agriculture in other species.”

Pocket gophers—brown rodents about the size and shape of a guinea pig—eat mostly roots, stems, and some aboveground weeds and grasses. They spend most of their lives alone in underground tunnel networks longer than a U.S. football field, going aboveground only occasionally to forage and mate. The animals spend a lot of energy digging out those long tunnels—an activity that also makes them vulnerable to predators.

To find out why they do it, Selden, an undergraduate at the University of Florida at the time of the study, and University of Florida ecologist Jack Putz went to Flamingo Hammock land trust, a communally operated rural acreage of which Putz is a partial owner, to study the southeastern pocket gopher (Geomys pinetis).

The researchers dug trenches around three tunnel sections at a time and placed metal oil barrels in each trench, keeping gophers out of those sections. Then, using a “borescope” camera (typically meant for plumbing and car inspection), they photographed the blocked-off tunnel sections as well as those the gophers regularly used. Roots of aboveground grasses and nettles quickly flooded all blocked tunnel sections, but stayed short in occupied sections.

Putz and Selden, who is now studying abroad in New Zealand, conclude the gophers were “cropping” the roots. The activity both fed the gophers and potentially stimulated root regrowth. The researchers note that unlike other gophers that stash waste in certain chambers, G. pinetis drops waste throughout the tunnels, fertilizing the soil.

Through root cropping and fertilization, southeastern pocket gophers are effectively cultivating a crop of roots that could provide more than 20% of their daily calories, the team reports today in Current Biology.  

Braude cautions that this isn’t advanced agriculture, which involves planting seeds and propagating crops. But he thinks the gopher’s behavior qualifies as husbandry, which involves harvesting a crop with restraint, saving and tending part of it to allow for future growth. He notes the gophers in most cases didn’t pull the entire plant into the tunnel and eat it, but left some for root regrowth.

University of Texas, Austin, evolutionary biologist Ulrich Mueller is more pessimistic. Mueller, who studies farming in insects, doesn’t think the gophers are doing any kind of farming, because they don’t plant or distribute their crop, as do humans and some other creatures, such as fungus-growing ants. The ants have evolved specialized pockets to transport fungus and a system of “weeding” pathogens out of fungi. There is no evidence for such evolved specializations or weeding in gophers, Mueller says, nor even evidence that the root cropping is anything more than an accidental byproduct of gopher activity. “We require something more than this … to call something farming.”

Whether farming or no, Putz hopes the study will open new lines of research into the behavior of other ground-dwelling rodents; they might also be root cropping or tending plants, he says, and no one has thought to look.

“If you go to the web and you put in ‘pocket gophers,’ most of what you’ll find is how to kill them,” Putz says. “My hope is that by demonstrating something fascinating about these animals, people will be happy to have them around.”