Grinnies – Something to Smile About

Grinny, ground hackee, chippie, hackle, and rock squirrel. These are some of the colloquial names for the Eastern Chipmunk (Tamias striatus). The name “chipmunk” is thought to come from the Ojibwe word ajidamoo, meaning “one who descends trees headlong.” Most people think chipmunks are only found on the ground, but they are actually very good climbers and will climb trees to gather nuts.

Chipmunks are easily seen now in the fall as they gather nuts and seeds for the winter. In a few weeks, they will retreat into their burrows and not emerge until mid-March or April, depending on temperatures and snow depth.

An Eastern Chipmunk’s burrow system is a maze of interconnecting tunnels, usually from 12 to 30 feet (4 to 10 meters) long and about 2 inches (5 centimeters) in diameter. Their tunnels are from 2 to 3 feet deep. A few deeper tunnels serve as drains to help prevent flooding. The main entrance is usually left open. There are also secondary escape routes plugged with leaves. A burrow will also have several food galleries, a chamber for waste, and a nesting area.

The Eastern Chipmunk’s stretchable cheek pouches can hold lots of seeds, which it carries to its underground storage areas. One animal was observed with 32 American Beech (Fagus grandifolia) nuts in its pouches. Another had 72 sunflower seeds. Now that’s one cheeky animal!

Even though you may not see them, chipmunks don’t sleep the winter away. Eastern Chipmunks are not true hibernators, but “catnappers” that undergo periodic torpor. Their deep core body temperature falls to as low as 40° F (4.4 ° C) and their heart rate slows to four beats per minute. After sleeping for a few days to two weeks, they wake up to feed and defecate. Research has shown that an Eastern Chipmunk stores 5,000 to 6,000 nuts to get through the winter! Juvenile chipmunks and those whose burrows were raided have been observed to scatter-hoard nuts by burying them in temporary caches and returning to eat them later. That’s one way nuts that aren’t eaten sprout into trees.

Chipmunks also feed on other seeds, fleshy fruits, leaves, worms, fungi, and occasionally bird eggs. They in turn are preyed on by hawks, coyotes, raccoons, foxes, owls, snakes, weasels, bobcats, and unfortunately domestic dogs and cats.

Although chipmunks vocalize to protect their territories from other chipmunks, they are famous for their high frequency “chip, chip” (actually ear-splitting up close). This often signals a ground predator (including us!) nearby. Years ago, I was stymied by a “cluck, cluck” sound I kept hearing in the forest. It was actually the sound a chipmunk makes when an aerial predator, such as a hawk, is nearby.

During a January thaw chipmunks can sometimes be seen at bird feeders eating sunflower seeds. They are diurnal, leaving their burrows during the day. This summer I have heard from many people wondering where all the chipmunks have gone. They are not as active during hot, windy, and rainy weather. Some stay in their burrows during much of July and August, which could be a response to scarce food and parasitism by botflies.

You might not be grinning when chipmunks dig up and eat your tulip and crocus bulbs. Plant these with one-half-inch hardware cloth over the bulbs, or in bulb cages, to discourage chipmunks. The plants will grow through the screening. You can also intersperse the bulbs with narcissus, which chipmunks don’t like.

Eastern Chipmunks are solitary creatures, except during two brief courting and mating seasons from February to April and again from June to August. Females will have one to two litters, each with three to seven young.

Although they occasionally cause damage to our plantings, chipmunks are an important part of our local forest ecosystem. They provide food for many other animals, aerate and drain soils, and spread fungal spores, which may create favorable conditions for tree seedlings.