While the last 3½ months have been memorably traumatic and disruptive for many human beings around here and the nation, one species has been having the time of its life. That would be the Eastern chipmunk.
The average furtive, scurrying rodent is unlikely to stand still for an actual head count — the census has a hard enough time with humans — but if you’re seeing more of them these days it’s not just because you’re spending more time at home due to a virus whose name will not appear in this article.
The Philadelphia region is one of the areas in which chipmunks evidently have experienced a population explosion in 2020, and that’s likely related to the legions of oak trees that produced extraordinary fall harvests of acorns, said biologist Carolyn Mahan.
Chipmunks are among the species that love those things, and can fit as many as six of them in their tiny mouths, which are equipped with marsupial-like pouches, Mahan said. She has watched un-resentfully as the little omnivores (they eat birds’ eggs) damage the plants outside her central Pennsylvania home and displace the gravel under her patio with their incessant digging.
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“They are amazing animals,” said Mahan, a Penn State professor who just might know more about their lives and times than any other human. She said that during one four-year period she spent about 2,000 hours studying them.
They run, they eat, they hoard, they dig, they chase rivals. In between, they sleep, and they reproduce in the spring and early summer, so another generation could be emerging on your property as you read this. They are polygamous, yet solitary, and usually masters at social distancing. They are only about six inches long, so the appropriate six feet would be roughly 12 chipmunk lengths. On average, a given acre might host only four to six chipmunks, yet these days it sure may seem like more.
If you see one in close proximity to another chipmunk, chances are it is chasing away a poacher, Mahan said; chipmunks are very territorial. Your plants and seeds belong to them.
As rodents go, the Eastern chipmunk ranks among the elite in cuteness.
But, yes, they do have darker sides. They can be a gardener’s worst enemy, consuming flowers and vegetables, says Chris Blake, an entomologist with Reading-based Ehrlich Pest Control, which serves customers in New Jersey and Pennsylvania.
“The chipmunks in my yard also get into the bird food and like to dig holes in the loose soil of the flowerpots where they find cached seeds,” Mahan said.
Said Blake, “The real problem with chipmunks are their burrows.” Their tunneling projects are remarkably complex. A map of their ingenious underground spaces would resemble one of those old gerrymandered Pennsylvania election districts. They have been known to undermine porches, decks, and patios.
They are constantly “improving” their burrows, Mahan said. Typically, Blake said, their burrows are several feet deep with annexes for sleeping tunnels and waste and food storage for their pilfered seeds and beloved acorns. And lately the oaks have been generous with their progeny.
Naturalists say acorn production has been particularly robust the last two autumns, and that might be tied to a vast conspiracy of the oaks.
The Philadelphia region is host to tens of millions of oaks, according to Ryan Reed, natural resource specialist with Pennsylvania’s Department of Conservation and Natural Resources, and each can shed tens of thousands of acorns.
A well-accepted hypothesis is that oaks vary their annual acorn output in an effort to confound their predators, hoping that maybe they won’t come back in a year after acorns are scarce. They have not been stingy lately.
Whatever the oaks are up to, apparently you can’t fool all the chipmunks all the time, and their stored autumn bounties have fortified them for the mating seasons. Those love fests usually occur in early spring and early summer. The gestation period is a mere 31 days, so you might see some newborns venturing out during the next few weeks, Mahan said.
As much as chipmunks like to hoard and feast, a host of other animals likes to feast on chipmunks. They are quite clever about hiding their burrows. They are careful to clear away loose dirt that might give away their entrances, lest they leave forwarding addresses to a long list of predators that includes cats, hawks, foxes, weasels, and owls, Mahan said.
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“That makes them a pretty important part of the food chain,” Mahan said, not something a chipmunk wants on its resumé.
For those who find chipmunks bothersome and don’t want to wait until predators do the dirty work, Ehrlich’s Blake said the best strategy is to keep them away from the house in the first place.
He recommends keeping piles of wood, vegetation, and debris away from the house. If you leave pet food outside, cover it, and by all means keep the birdseed as out of reach as possible.
For her part, Mahan has no issue with sharing her property with chipmunks even if they are making a mess of her patio gravel. “Because I study them, I’m really tolerant of them,” she said.
She declined, however, to speak on behalf of her husband.