September 29, 2023

Rural way of life in rodents?

Rural way of life in rodents?

A study showed that they don’t just eat whatever comes their way while digging: gophers “plant” and harvest roots that sprout in their underground tunnels. According to researchers’ calculations, regrown forage covers 20 to 60 percent of ground squirrels’ daily caloric requirements. They argue that this is the first example of a system in a non-human mammal that could be called agriculture. However, the definition of the term is important, scholars acknowledge.

Usually, animals eat what they find or capture – even our ancestors lived this way as hunters and gatherers. But then man began to supply himself with food that he had gained through the targeted care of plants and animals. There are also examples of this peasant way of life in the animal kingdom: some species of ants and termites grow mushrooms to feed themselves. Apart from us, no similar behavior has been known from the group of mammals for food production. But now biologists Francis Putz and Veronica Selden of the University of Florida in Gainesville have concluded: “Southern gophers are the first known non-human farmers of mammals.”

Tunnel systems on the horizon

These rodents, widespread in North America, are not usually seen – they are usually only noticeable by small mounds of land on the surface of the earth. It’s underground digging: gophers dig a vast maze of twisting underground tunnels. The study began by asking how animals can find enough food when digging for a net gain of energy – because digging is very laborious. So the suspicion arose that the animals might not have to dig much. One indication was the well-known problem that roots tend to grow in the sewage system, which are fertilized with droppings, and they must be removed regularly. “If roots grow in these man-made tunnels, we thought they might also grow in these rodent tunnels that are fertilized with feces,” Selden says.

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So Putz and Selden decided to pursue their suspicions in a targeted way: In their study, they used an open-air gopher tunnel system to record how much root mass grew in underground cavities. As they reported, this involved a lot of excavation and one of the main challenges was keeping the rodents out of the investigated tunnel area so that they could not harvest there during the investigation period of a few months. The researchers finally managed to do this with a few tricks. This enabled them to determine the root growth rate and to estimate the energy content of the substance that a typical tunneling system could provide. The scientists were then able to correlate these results with estimates of the rodents’ energy requirements.

A rooted farm is emerging

Calculations and comparisons have shown that tunneling will cost much more energy than existing forage can provide. However, by harvesting roots growing in the tunnels they’ve already dug, gophers can get enough energy to keep digging tunnels in search of more food: the daily harvest covers 20 to 60 percent of the rodents’ energy needs, estimates came. “In the tunnels it’s as dark and damp as in a sewer pipe, and there roots grow like stalactites and stalagmites,” Putz says. “The animals there provide an ideal environment for the roots to grow in and fertilize them with their waste,” continues Selden. According to the researchers, the importance of the extensive tunnel system explains why it is so well maintained and defended.

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By encouraging the growth of roots in their tunnels and then harvesting them, it is a form of food production that can be called agriculture, the scientists say. “It depends on the definition,” Putz says. “If farming means growing crops, gophers don’t count. However, to someone with a more gardening perspective, where plants are as carefully looked after as fruit trees in a forest, that seems a very narrow definition. Many cultures around the world have developed a form of Forms of cultivation are based on perennial crops, many of which are not grown, only cared for. I think the question of definition is interesting because it hasn’t really been clarified,” says Potz.

“Regardless of whether gophers are considered to be animal farmers or not, their behavior should be studied further,” the researchers wrote. This may explain to what extent the animals create optimal conditions for root growth and whether they also harvest the fungi in their tunnels. “The (surats) may seem vague at first, but this is deceptive. They deserve our attention,” concludes Selden.

Source: Cell Press, University of Florida, article: Current Biology, doi: 10.1016/j.cub.2022.06.003