The Secret Lives of Chipmunks

By Rosemary Jann

We have always lived peaceably with our backyard chipmunks. I knew that they had burrows under the cement pad for the AC and behind the garden shed.  But when I found a new burrow hole right up against the foundation of our house, I confess I had the urge to declare war.

Arlington’s local chippies are Eastern chipmunks (Tamias striatus) and members of the squirrel or Sciuridae family. Their scientific name means “striped storer,” a reference to their characteristic field marks: white stripes bordered by black on each side of their backs plus a black stripe down the centerline, as well as white stripes around their eyes. Adults weigh in at 5 oz. or less and measure about 10” long, including their bushy tails, which they hold high while running. And they’re usually on the move when you see them, since their small size makes them vulnerable to predators. According to the Mother Nature Network, these include hawks, owls, foxes, snakes, and, especially in our backyards, free-roaming cats. An article in the Journal of Mammalogy explains that chipmunks have different calls to warn about different predators: a chip for terrestrial foes and a cluck for aerial ones, plus a chip-trill when they’re being pursued. This National Geographic page on chipmunks includes a video with these three calls.

Chipmunks are also constantly on the move because they need to use every daylight hour to collect food, especially in the fall. The National Wildlife Federation describes them as omnivores who will eat fruit, nuts, grain, berries, insects, fungi, small amphibians, and even bird eggs or nestlings if they find them on the ground. According to the Mother Nature Network, their cheeks can expand to three times the size of their heads to carry food.

Alonso Abugattas, the Capital Naturalist, notes that since they mostly consume seeds and nuts within their burrows, chipmunks are not a significant source of seed dispersal. But their appetite for mushrooms does help to distribute mycorrhizal fungi that is beneficial to trees and plants.

In their underground burrows, chipmunks create multiple food caches that will sustain them through the winter months. They are not true hibernators, but rather exist in a state of torpor, waking periodically to eat. The National Wildlife Federation mentions scientific studies suggesting that global warming may be undermining chipmunks’ survival rates by disrupting their normal hibernation cycles.

Their underground burrows can be up to 30 feet long and have at least two widely spaced openings. Nesting areas are separate from food caches. The Mother Nature Network describes chipmunks as generally solitary except for mating, which occurs in the spring and sometimes again in late summer.  The female raises 2-5 pups, who leave the nest and go off on their own within 6 weeks.

Although typically forest dwellers, chipmunks have adapted readily to suburban environments and thus can come into conflict with people by eating bulbs, raiding bird feeders, and digging too close to foundations. Although they do carry ticks,  the Humane Society notes that chipmunks themselves are not known to spread diseases to humans, and their burrows seldom cause significant structural damage. The Society advocates tolerance rather than termination and various methods to deter them: move bird feeders at least 15 feet from your house, sweep up spilled seed, avoid plantings close to your foundation, use wire mesh to protect bulbs.

I wound up following the advice of the Bi-State Wildlife Hotline and placing a rag soaked in ammonia and a cup of moth bulbs near the new foundation hole. That way I can remove both without harming the soil once the chipmunks have relocated. The Hotline also mentions various commercial and home-made remedies to discourage them from chewing on decks and fencing.

Everyone has a different level of tolerance when it comes to living with backyard wildlife. In stepping back from the brink of war, I’ve reminded myself that the rewards for learning to coexist with chipmunks are supporting a more diverse ecosystem and enjoying the continuing antics of these tiny, charismatic neighbors.