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Davis, California

Saturday, February 24, 2024

Invasive squirrel reproduction controlled by campus efforts

Any lady squirrels out there not looking for anything serious? Keep your eyes peeled for males with ear tags and dyed fur.

Not only have these males adopted human fashion trends, but they are also among the 68 squirrels that have already been given hormone injections to stop them from reproducing as part of an experiment to control the population of Eastern Fox squirrels on campus.

“There has been no noticeable increase in the population of the Eastern Fox squirrel,” said Sal Genito, director of the Buildings and Grounds division of Facilities Management. “What I can tell from observing myself, I believe that the population is pretty much stabilized.”

Eastern Fox squirrels (Sciurus niger) are between 10 and 15 inches long and weigh between 1.5 and 2 pounds. They can be identified by their orange-brown colored coat and bushy tails with reddish-topped hair, according to Americazoo.com. Cute as they may be, they don’t belong here and are disrupting the ecosystem, said Sara Krause, the doctoral student from the Department of Ecology who is in charge of the program.

“They’re an invasive species in California,” she said. “They have no natural predators in the area, especially not on campus.”

Getting their population to “plateau” is the first step to the birth control research program, which began last November when Department of Ecology faculty and staff began laying traps. The wire mesh traps invite the squirrels to eat the acorn before the box shuts. The boxes are covered with canvas and feature plenty of room to move around.

Captured squirrels were examined, marked with a dye and freed throughout last fall and winter before they were administered the hormone shots this summer.

Once the population plateaus, the goal is to reduce it to a small, sustainable number in five to 10 years. In the meantime, the squirrels will continue to aggravate the grounds crew and tree lovers, said Genito.

“The damage they’re doing is of concern – because they use a lot of the large redwoods as nesting sites, and if you look closely, there are several ‘runways’ going up in to the trees,” he said.

Genito likened it to students strolling through grass as a shortcut in class, rather than taking a paved walkway.

“Damage just occurs as a result of frequent traffic. It’s especially harmful to the Redwood population.”

Other campus fixtures the squirrels have enjoyed include sprinkler heads – both for teething and relief on a hot summer day.

“They’ve been gnawing on sprinkler heads all over,” said Krause. “And they have to be replaced much more frequently because of it.”

But the main reason Krause and her team undertook this project is not to keep UC Davis grounds workers from becoming Bill Murray’s character in Caddyshack, but to restore the ecosystem to its original state – before the invasive species arrived.

The non-native squirrels create competition with plants and animals that are native to the area, said Krause.

“Eastern Fox squirrels eat the same foods as native gray squirrels and birds,” she said. “They have also been known to eat eggs and baby birds.”

Crops threatened by overpopulation include almonds and walnuts at campus research farms and orchards, as well as the bark of redwood trees in the arboretum.

Krause said that, should the experiment continue to go as planned, the next step is to gain EPA approval for commercial use.

“We’re pretty optimistic that it will continue to work similar experiments already have on other species,” she said. “With the conclusion of this study, we’ll have a model for how this can work in a community and specifically, how we can make it work for our campus in the long run.”

Genito said they’ve reached out to the city of Davis and found interest, but that current budget constraints may be a limiting factor in starting a project such as this one.

Eastern Fox squirrels taking up residence elsewhere is a concern though.

“Just because we’re doing what we can to do birth control here doesn’t mean the squirrels won’t move to a nearby location at some point,” Genito said.


MIKE DORSEY can be reached at campus@theaggie.org.






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