Cal State L.A. students examine the rivalry between native and newbie squirrels

Western gray squirrels are competing for space and food against Eastern fox squirrels | Alan Muchlinski


EL SERENO — It’s two squirrels in SoCal. One local, one imported. One, a big fluffy-tailed specialist (the Western gray) with a penchant for pine trees and tree nuts that used to rule the roost in SoCal. The other, a red-furred sleek generalist from the East Coast (the Eastern Fox), a fast procreator with an appetite for everything. To call this a mismatch would be an understatement.

As a biological sciences professor at Cal State LA, Alan Muchlinski has been a faculty advisor to many grad students learning how the Easties are affecting SoCal’s grays. His latest is Chris DeMarco whose thesis project involves collecting and interpreting genetic samplings of gray populations. He’s targeted populations in the Santa Monica Mountains, Griffith Park and Rancho Santa Ana Botanical Gardens.

“So many people would say, ‘What’s the big deal? One species replacing another? What does it matter?’ But the reality is introduced species cause problems with the natives and affect the ecosystem,” Muchlinski says. “We just don’t know what the complete consequences are.”

The Western gray squirrel (left) is a SoCal native; the Eastern fox squirrel (right) was introduced in the area a little more than 100 years ago | SoCal Wild

The frisky Easties found passage to Los Angeles around 1904 to the Veteran’s Hospital in West LA, where they were “pets” to residents. At first, no one seemed to mind when a few escaped into the ‘wild’, but then damage to local fruit and nut trees became apparent and the pets quickly turned into pests. Through the years, people have been trapping and dumping them in other locations thus exacerbating the bigger problem.

DeMarco collects genetic material from strategically placed “hair tubes” that are stuffed with walnuts and other squirrel delights – and sticky tape inside collects critter’s hairs. These follicles contain DNA which DeMarco uses to chart lineage of the grays, estimating how genetically diverse these populations are and if there is any genetic flow between populations.

Comparing gray maternal genetic profiles in Griffith Park, DeMarco is discovering disturbing trends – basically, gray squirrels’ genetic makeup is similar because they are inbreeding. Even though squirrels are known for their acrobatics and wire walking abilities, the grays find it difficult to branch out beyond their original homes. Traffic and human development keep them stuck. Besides isolation, grays are up against other factors: poisons, roadkill, destructive fires and competition with the Easties.

Squirrel hair samples collected for DNA testing| Chris DeMarco

“Studies have shown it’s possible for grays and Eastern fox squirrels to coexist,” says DeMarco explaining that in areas with a wide diversity of tree species – like Griffith Park’s Ferndell – there is a higher proportion of Western grays. “There could be a way to sustain these two species if there were more pine, walnuts and sycamore trees in the area, trees the grays like. In Ferndell, grays and Eastern fox squirrels seem to coexist for the most part.”

But the question is for how long? Muchlinski isn’t sure, but he does know that if the Easties move into SoCal’s forested areas – Big Bear, Mt. Wilson – that could be catastrophic for SoCal grays. “It helps if people understand that it’s not good to move non-native animals around,” he says.

All in all, Griffith Park is snapshot of SoCal squirrel-ness. “By seeing what is happening here, we can start to target and suggest ways to circumvent any potential extinctions of one of the sub populations,” says DeMarco. “If populations become so isolated and are in a dire downward spiral, it may mean special action.” Conservation possibilities: adding more gray-friendly trees, introducing grays from other areas into that population to beef up the gene pool, and create corridors for squirrels to scamper in and out of isolated habitats.

When his research wraps up next year, DeMarco will share it with local agencies like LA Park and Rec, National Park Service, etc. “Genetic studies have been done on the gray squirrel in Washington and Oregon but not here,” he says. “We, California, need to catch up.”

This story originally appeared in SoCal Wild.

Brenda Rees is a writer and resident of Eagle Rock.

A map of Griffith Park’s gray squirrel distinct sub-populations | SoCal Wild

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