According to new research from the University of Florida, roots grow into the humid tunnels of southeastern pocket gophers (Geomys pinetis) where they benefit from nutrients from gopher wastes; cropping these roots supplies the animals with an average of 21% but up to 62% of their daily metabolic needs.
Southeastern pocket gophers are solitary, root-eating fossorial rodents native to North and Central American grasslands.
These enigmatic creatures acquire most of their food through excavation of tunnels maintained as part of tunnel systems up to 160 m long.
Although often thought of as pests, they eat only roots and rarely damage crops. Nor do their strong tunnels undermine the ground.
“They live entirely alone in a tunnel system that’s 100 m long. Dark and wet like a sewer pipe,” said Professor Jack Putz, a researcher in the Department of Biology at the University of Florida.
“The roots grow in like stalactites and stalagmites. They cover the walls of their tunnel.”
Professor Putz and his colleague, Veronica Selden, were puzzling over how the gophers got enough energy to dig when they recalled the perennial problem of roots growing into sewer pipes in homes.
“If roots grow into these man-made tunnels, perhaps they’ll grow into these gopher tunnels that have waste to fertilize them,” Selden said.
The study authors spent months trying to keep gophers out of their tunnels so they could measure the roots that grew back in.
Using dams of wood or metal, they attempted to block the gophers from their tunnels, but to no avail — the gophers merely went around.
Eventually, they turned to large drums with the ends cut off. After even more digging, they placed the open side of a drum into the soil to surround a patch of gopher tunnels while allowing plants on the surface to keep growing. The cylindrical shape provided 360 degrees of protection from gopher interference.
Calculating the daily rate of root growth allowed the team to calculate how much of the gophers’ energy needs could be met by harvesting their crops.
The researchers discovered that digging a tunnel costs far too much energy to be made up by the roots gophers eat while excavating.
But, by harvesting the roots that grow into already-dug tunnels over time, the gophers can gain enough energy to keep digging tunnels in search of more food.
“Planting the crop, for some people, is what constitutes agriculture. Yet many other animals, and also different human cultures, use horticultural techniques to tend to crops they don’t plant themselves,” Professor Putz said.
“I think the whole issue is intellectually exciting because it’s not really settled.”
“Pocket gophers are a lot more interesting than people give them credit for. They’re really important ecosystem engineers. They deserve more attention,” Selden added.
The team’s paper appears online today in the journal Current Biology.
V. Selden & F.E. Putz. Root cropping by pocket gophers. Current Biology, published online July 11, 2022; doi: 10.1016/j.cub.2022.06.003
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