Life Underground: The Secret Life of Chipmunks

Ah, our dear, sweet, beloved chipmunks. We feed them and watch them scurry off, diving down a hole perfectly shaped to their stocky bodies, disappearing for a few minutes and coming back for more. This game seems endless and always has me wondering what they're doing with all that seed, and what it looks like inside of that mysterious hole. When I think of the inside of a chipmunk's burrow, I envision it to look identical to Smaug's Lair in the Hobbit, only instead of gold and jewels, it's filled with peanuts and seed "pillaged" from my bird feeders. But a chipmunk's burrow is much more complex than just a giant heap of goodies, and involves some serious planning in order to survive. 

Eastern Chipmunk (Tamias striatus)

Though chipmunks are known for being bold and even friendly when it comes to their relationship with humans, they live a life of solitude. Each chipmunk has its own burrow and home range, never living communally. Even during mating season (mid-April to mid-May), the pairings take place outside of the female's burrow, and she raises the young alone. A chipmunk's home range is the area surrounding its burrow, where it travels to forage for food, water, and to seek out potential mates during breeding season. Home ranges can vary in size between 0.04 and 1.26 hectares, with males typically having larger ranges than females. These areas do not strictly belong to one chipmunk, and frequently overlap with several individuals. When crossing each other's paths in their home ranges, chipmunks will usually tolerate one another and go about their business alone. 

The burrow is where a chipmunk's dominance and territorial behaviours come into play. There is no overlap of territory in these areas, and if one chipmunk comes within close proximity to another chipmunk's burrow, the owner will pursue and chase the intruder away from its home. Chipmunks use scent marks to mark their territory and communicate to others that a certain space is their dominance area. When a chipmunk is near another individual's burrow, it will typically avoid the area, but some may wander a little too close for comfort for the owner resulting in an exchange of words, a chase, and occasionally, a scuffle. 

A chipmunk's burrow is made up of several tunnels, pockets, and chambers. There are several entrances to allow for a quick escape from a predator (such as a snake), collapse, or flooding, all of which are typically camouflaged under rocks or bushes. All entrances lead to the main nesting chamber, where the chipmunk sleeps, and spends much of its time during the winter months. The nesting chamber is lined with insulating materials like leaves, grasses, and thistledown, and often has a store of food underneath for easy access in cold weather. Along each tunnel are side pockets used to store food and empty shells, and are sometimes used for the chipmunk to easily turn around in narrow spots. Lastly, narrow drainage tunnels are dug at the bottom of the burrow to help carry water away. Researchers have found no evidence of a latrine (or bathroom) inside of the burrow, so it is believed that the chipmunk must leave the area to relieve itself. 

This elaborate home is where a chipmunk will spend most of the winter. Beginning around mid-summer, the chipmunk will begin collecting food to add to its hoards for the upcoming winter months. By November, most chipmunks have enough food stored to last several months and disappear underground. It's not currently known exactly what a chipmunk does once it retreats to its underground bunker, but there are two plausible theories. One theory is that a chipmunk remains awake and active until its food stores are depleted, then goes into a state of hibernation known as torpor. And the other theory is that it immediately goes into a state of torpor, leaving its stash for later. Torpor is an involuntary state of hibernation where an animal is able to lower its body temperature, heart rate, metabolic rate, and breathing rate, in order to expend less energy and survive the cold weather. Torpor is different from true hibernation in that it lasts short periods of time (typically days), and allows for the animals to wake, feed, and relieve itself in between. Emergence from a torpid state is triggered by ambient temperature and food availability, and takes approximately one hour to recover from. This lasts about four months, with chipmunks beginning to leave their burrows to forage and find mates as temperatures warm in March.

Eastern Chipmunk

A chipmunk's burrow is the most important part of surviving in the wild - it is a place to sleep, eat, hide from predators, raise babies, and hibernate. Cooler weather is fast approaching which means our beloved chippys will be retreating to these elaborate subterranean lairs to ride out the winter. And although I now know what their life underground entails, come January I think I will still picture an overindulged chipmunk laying over a pile of nuts & seeds that I've helped provide, living its best life until spring arrives and it begins the cycle again. 😉

Happy trails!

- Shayna