Ground Squirrels: Both Pest and Keystone Species

Sheila Barry
Sep 6, 2018 · 6 min read

One squirrel is clearly visible through the plexiglass window built into the top of the square, wooden box. The window mostly frames its body, covered with mottled greyish brown fur. The squirrel’s dark round eyes, ringed with white fur are wide open and it is standing perfectly still. Inside the box, the size of a dishwasher, are four traps each with two to three squirrels inside. A clear tube entering the bottom of the box is attached to a tank of carbon dioxide, the kind of tank that is more often hooked up to a soda fountain dispenser.

The research assistant turns on the valve on top of the tank and then removes four more wire traps with captured squirrels from the back of his pickup. He stacks the traps next to the box. “I keep the carbon dioxide flowing into the box for about 8 to 9 minutes,” he explains. “Right before they die they will take a couple of deep breaths.” As if on cue, the animal’s sides inflate and deflate and then it’s perfectly still again.

It’s the beginning of August and the research assistant has been trapping and killing rodents on farmland in San Jose, California for the past couple of months. The farming enterprise is growing fruit, vegetables and herbs. Ground squirrel control efforts are essential. This past spring squirrels took out rows of vegetable seedlings and sampled numerous melons and other fruits, resulting in 70% of the crops being lost.

During the winter phosphine gas pellets were tossed into hundreds of squirrel holes to control ground squirrels. There is no way to know how many squirrels were killed by the fumigant but a whole new crop of squirrels was born in the spring. In just 8 weeks during the summer, trapping efforts eliminated 241 California ground squirrels from 8 acres of farmland.

When the research assistant started euthanizing trapped squirrels, he would watch them take their last breaths through the plexiglass window. He was learning to calibrate the gas flow into the box. Calibration also includes knowing how long to wait before opening the box and exposing the squirrels to air. A squirrel that looks dead may revive with fresh air.

“See that stick?” the research assistant asks while pointing to a thin foot-long piece of steel rebar near the box. Following the information provided by the University of California on best management practices for ground squirrel control, he pokes them in the eye to be sure they are dead. “Dead squirrels don’t blink,” the research assistant says, as he removes a trap with now-dead squirrels from the box and dumps their lifeless bodies into a garbage bag. “I don’t watch them die anymore,” he says.

Not everyone agrees that they should die, at least not by human hands. Just a few miles away from the farm land, there is a wildlife rescue center being operated out of home that specializes in rescuing California ground squirrels. Like several other wildlife rescue centers in the San Francisco Bay Area, this rescue center rehabilitates injured and orphaned animals, returning them to “the wild” whenever possible.

Sometimes it can seem as if all their work is for naught. The woman who runs the rescue center once spent three months nursing a squirrel to good health only to see it get scooped up and eaten by a hawk when she released it into the “wild”. “I would have preferred that it lived a day or two, but at least that is what was supposed to happen. It’s part of a food chain,” she explains. “We are all part of a food chain, but people just don’t understand that.”

Lethal animal control and wildlife rescue — reflect opposing perspectives about the value of wildlife and our tolerance for their impacts.

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It is just a couple weeks after the research assistant was killing trapped squirrels in the wooden gas box. He is next to the farm field checking traps like he does every Monday morning this fall. An electric bell squawks from a nearby Elementary School. A couple of squirrels stand outside of their burrows like sentinels. They pay no mind to the bell’s loud bleep run-on sentence nor do other wildlife.

A hawk and a bald eagle have recently been spotted on the farmland. The research assistant saw the hawk swoop down and grab a couple of pigeons for lunch. “They must be easier to catch. We need him to eat 10 to 20 squirrels per day, although we have a pigeon problem too,” the research assistant admits with a sigh. “But, I’m glad he’s here.”

Who knows? Other predators might eventually also take up residence in the park. Perched high above the chain link fence that separates the farm fields, there are a couple of small white boxes ready for owls to move into. However, predators can’t be expected to eliminate their prey. They will need a healthy population of squirrels (or pigeons) to maintain their residence in the park.

Encouraging squirrels’ predators to move into the park “to restore the primitive balance” is an effort toward coexistence. The wildlife rescue woman champions this effort. “Do you know what the most territorial species is in the world?” She asks and then answers her own question. “Humans. Why do we think our needs take precedent over all others? We need to cohabitate.” Without a pause, she acknowledges the challenge in this. “But even people can’t seem to cohabitate with one another,” she says.

Even if there were numerous predators, cohabitation or coexistence in the agricultural park seems idealistic. When a farmer new to the area started farming nearby last year, he thought coexistence with the rodents was possible. He noticed a few ground squirrels scurrying around his waiting-to-be-farmed fallow field but figured they would not cause much of a problem.

They did. In a matter of days, squirrels pulled up or completely chewed off 20 rows of watermelon seedlings. Essentially his whole crop of watermelons was gone. Now the new farmer is not taking any chances. “There’s no sharing,” he says. “If the seedlings survive, they [the squirrels] come back later to take a bite of the fruit.” He needed bait more enticing than what he is growing. Since the seedling loss, he has been trapping squirrels with cat food.

The squirrel’s preference for our food crops is a challenge for coexistence. Farm crops — small grains, fruit and vegetable crops — have always been more enticing to a ground squirrel than their native diet of natural growing grasses, broad leaf plants and seeds. Loss of crop and damage to irrigation lines and other infrastructure leaves farmers wanting to eradicate squirrels from their farmland. As one farmer stated, “they serve no ecological purpose.”

Well, maybe on the farm. Outside the farm gate, they have a purpose. The wildlife rescue woman explains their ecological purpose as if we should have understood it all along. “A squirrel digs a burrow. It leaves that burrow and digs another one. Something else like a frog, owl or salamander moves in. Then the squirrel is lunch or dinner for a hawk or eagle.”

Although ground squirrels’ role in providing food and shelter for other species is nothing new, ecologists have only recently recognized its importance. In 2007, a local ecologist researching the ecological role of ground squirrels, was among the first to describe the rodent as a keystone species. She recognized the ground squirrel’s presence in California’s grasslands was key to the survival of other species, including a couple species with special federal and state protections. The squirrel’s association with special status species has required some land managers to limit or eliminate control efforts and allowing squirrels to co-exist with other land uses.

On ranches and open space lands throughout the South Bay, ground squirrels and species that depend on them, including two endangered species, coexist and thrive with cattle ranching. Although from time to time ranchers may also control ground squirrel populations. “When squirrel colonies grow, creating too much bare ground and too many holes, ranchers poison squirrels,” a local rancher explains. “We don’t do it every year. Only every eight years or so, and only in areas with large colonies.”

Sheila Barry

Written by

Livestock Farm Advisor, Animal Scientist, California Certified Rangeland Manager, Complex Systems Researcher, Omnivore