The farmer mammal family has been joined by the southeastern pocket gophers, according to new research.
While they may not plow huge fields or drive combine harvesters, pocket gophers (Thomomys bottae), burrowing rodents native to North and Central America, also practice their own brand of farming. These animals keep ahead of their energy-intense burrowing lifestyle by actively tending to root systems growing through their tunnel networks.
According to a newly-published study, the gophers get anywhere between 20 and 60% of their daily energy intake from farmed roots.
Growing their own
“Southeastern pocket gophers are the first non-human mammalian farmers,” says Francis Putz, Distinguished Professor of Biology at the University of Florida, Gainesville, one of the two authors of the study, in a press release. “Farming is known among species of ants, beetles, and termites, but not other mammals.”
“Around the world there are many species of fossorial [i.e. burrowing] mammals with habits similar to those of the southeastern pocket gophers we studied. Perhaps among them are other farmers,” he added for ZME Science.
Pocket gophers live solitary lives just below the surface of grasslands in North and Central America. They build extensive tunnel networks in which they reside most of the time, seldom finding themselves above ground. These tunnels are known to act as shelter and larders for the animals, but it seems that they also act as a source of food.
In an email to ZME Science, Prof. Putz explains that the research was spurred by a “general interest in the natural history of these little-studied beasts”. But the research took on a new life as Putz and one of his students, Veronica Selden, first-author of the paper, started doing the heavy lifting required to actually study these rodents. I asked the professor what first clued them in to the fact that the gophers may be up to some farming, and he replied:
“The tunnels are so deep in the ground, well below the depth at which roots are abundant. By digging ourselves, we were reminded of the energetic cost of that activity”.
The Gophers don’t just eat roots that they happen to find while digging, the authors explain. Instead, they nurture the roots that they encounter, providing them with favorable conditions to promote growth. For example, they use their own waste as fertilizer.
“By leaving their urine and feces throughout their tunnels, rather than in specialized places (i.e. latrines), the fertilization effect is more widespread”, Prof. Putz explains for ZME Science.
Unlike how people handle farming, gophers prefer to go at it by themselves rather than work together. They are “entirely independent”, Prof. Putz adds, only being social “when they are mating, but afterward, they return to their own tunnel system, which they defend against all comers”. This extreme territoriality is a feature that makes gophers stand out from most other rodents in general and other ground squirrels in particular, to which they are related. It is possible that the gophers’ reliance on their root crops for survival promoted this territorial behavior throughout their evolutionary history.
The team argues that, as these animals employ a system that promotes the growth and development of roots which are then cropped or harvested entirely, the southeastern pocket gophers are, essentially, employing a system that qualifies as farming.
“It really depends on how ‘farming’ is defined,” says Putz. “If farming requires that crops be planted, then gophers don’t qualify. But this seems like a far too narrow definition for anyone with a more horticultural perspective in which crops are carefully managed—such as fruit trees in forests—but not necessarily planted. With this perspective, the origins of agriculture included Mesopotamian annual cereal and pulse crop cultivation as well as maize cultivation in the Americas, but many cultures around the world developed agriculture based on perennial crops, many of which they didn’t plant but did tend.”
The two authors explain that this root-farming behavior of gophers may explain why they need to build, maintain, and defend such extensive tunnel networks. They aren’t just homes or storage space that the animals expand for no reason — they are akin to crop fields.
For now, the team plans to expand their research to see whether gophers also farm and eat fungi, and to record how the seasonal variation in the energy contribution of their farmed roots relates to their activity cycles. It’s also not yet clear how their work underground affects surface vegetation, another promising avenue of research that the team is considering.
“Pocket gophers are great examples of ecosystem engineers that turn over soil thereby aerating it and bringing nutrients back to the surface,” says Putz. “They eat only roots, some of which they grow themselves, and seldom interfere with human activities.”
“One motivation for studying pocket gophers is that too many people kill them for no particular reason,” Prof. Putz told me. “If you Google ‘pocket gopher’ you will see that the web is full of devious ways to kill these harmless little animals, from snap traps to drowning, not to mention various poisons.”
“We hope that our discovery of this remarkable behavior will cause more people to understand gophers and leave them alone.”
Apart from direct efforts to exterminate them, gophers also face some pressure from habitat destruction, Prof. Putz adds, “but they are fairly adaptable, happy in pastures and lawns as well as in natural savannas and grasslands”. He believes that helping people better understand the gophers will help ease some of the pressure they are facing, as “the first step towards nature conservation is developing an appreciation for nature” — and that all starts with knowing what there is to appreciate.
In closing, Prof. Putz says he is “thrilled to have participated in a discovery with an undergraduate student, working on a project that involved a lot of shovel work but no big research budget — old-fashioned natural history done in a backyard.”
“The moments during the research that I found most endearing were when we failed, sometimes after great physical effort, but laughed at ourselves and continued digging.
The paper “Root cropping by pocket gophers” has been published in the journal Current Biology.