Chipmunk
Introduction
Chipmunks are small rodents in the same family as squirrels. The species in the genus Sciuridae can be divided into flying squirrels, tree squirrels and ground squirrels. Chipmunks, as well as marmots, woodchucks, and prairie dogs are part of this family as they are classified as ground squirrels.
How can you tell chipmunk from a squirrel? Chipmunks are less than half the size of a squirrel and weigh only about four ounces. Chipmunks also have black, brown, or white stripes running along the sides of their faces and backs, and their tails are shorter and have less fur.
In BC we find four species of chipmunk:
- the Least Chipmunk,
-the Yellow-pine Chipmunk,
-the Red-tailed Chipmunk and
-the Townsend Chipmunk
The Townsend Chipmunk is the species you may have seen in our area and is frequently referenced on this webpage. Also we thought you might like to see the world-wide cast of chipmunk characters, so here they are all 25 of them. Apparantly each one is distinctly unique and identifiable, if you have a sharp eye, that is. To help, we’ve highlighted the aforementioned BC residents.
To introduce you to how appealing these little creatures are, watch the following short video and listen to its vocalizations that we often mistake for bird chirps.
Range and Habitat
In North America, you will not find chipmunks in hot tropical forests, in areas of waterlogged soils, in prairie grasslands or north of the Canadian tree-line. With those exceptions, chipmunks thrive throughout Canada, the United States and even into southern Mexico along the mountains.
The Townsend Chipmunk lives in the forests of the Pacific Northwest and is found in the southwestern corner of BC and through western Washington and western Oregon.
Chipmunks inhabit boreal and temperate forests preferring the forest edges and openings. They are common in coniferous forests, deciduous woods, sagebrush, clearcuts, and open jack pine stands. They can often be found near rock cliffs, river bluffs, and riparian areas.
Physical Characteristics
The Townsend Chipmunk is larger than many other chipmunks, measuring up to 38 cm. (15 in.) from nose to tail and weighing in at an average of 75 gm. (2.6 oz.). Females are often slightly larger than males.
These chipmunks are brown in colour with indistinct tawny stripes. There are five dark stripes and four lighter stripes on their back and two grey and three brown stripes on their faces. You know you are looking at a chipmunk rather than a squirrel if you see stripes on the face.
Bellies are creamy white or grey. Their bushy tail, held erect while running, is greyish above and reddish brown below. Their ears are black in front and grey behind.
Do not be alarmed if you encounter a naked Townsend in May or August as they moult twice per year, losing their fur and quickly regrowing it. Their fur colour becomes brighter during the summer.
All chipmunks have very nimble, adept front paws, specialized sharp cutting teeth and extensible skin in the cheek area that form pouches. The following video will show you how these physical characteristics enable the chipmunk gather food and put it in “shopping bags” to transport back to its burrow.
Communication
Chipmunk communications include recognizable calls that are predator warnings, mating intentions, nesting instructions or “stay-off-my-turf” cautions.
Chipmunks make 3 distinct sounds when they are reacting to a threat. The first is a uniform, high-pitched “chip chip” that indicates a ground predator such as a raccoon. The second is a deeper, robust “chuck chuck” delivered while standing motionless that is intended to draw attention to an airborne threat such as a hawk. The third is a short sharp trill that is delivered on the run and means “take cover just as I am doing.”
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Trilling sounds express alarm or excitement. Chipmunks also make a trilling sound when they spy a potential mate. In the late spring, it is common to see chipmunks rub noses and to hear a “croak and chirp” sound that is common to mating season.
Chipmunks also use a range of loud chirps as well as body language to protect their burrows and occupied territory, to show dominance, or to warn their young of danger.
Life Cycle
Chipmunks are generally solitary animals, socializing only when mating or raising offspring. Little information exists on the Chipmunk’s reproductive process. Males are known to emerge from their burrows one or two weeks ahead of females. Mating takes place outside the female’s burrow in mid-April to mid-May. It is thought that either males mate with more than one female or both genders have multiple mates. A female will retreat to its burrow to birth and raise her young without the help of the male. Chipmunks usually breed once a year, although a second litter may be possible if the first litter is lost.
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At the end of a 30 day gestation period 2 to 6 young are born. Because newborns stay in the burrow for the first 6 weeks, when they venture into the outside world they look like small adults. But as newborns, they are naked, hairless, pink, blind, helpless and the size of a bumblebee.
Their ears are closed until around the 28th day, their eyes open at 31 to 33 days and a full fur coat is acquired by 40 days. During this time the female is an attentive mother; protective and caring until she weans her young at about 60 days.
The young will reach adult size in September. They leave their mother at 8 to 10 weeks. The age of reproductive maturity is between 10 months and a year. In the wild, a chipmunk’s lifespan is 2 to 3 years.
Burrow
A chipmunk’s burrow is central to its survival. It is a place to sleep, eat, hide from predators, raise babies, and spend the cold days of winter. Each burrow holds only a single occupant with the exception of the time when a female is raising her young. During its life, a chipmunk will rarely venture more than 1/3 of a mile from its burrow.
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Chipmunks are prey for many larger animals, so they choose a burrow site with plenty of ground cover, including logs, trees, stumps, shrubs and rocks.
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The design of a chipmunk's burrow is really quite amazing….multi-purposed and expansive. They dig an entrance hole 2 inches in diameter and then tunnel down to about 2 or 3 feet. While excavating, they make use of their cheek pouches to return dirt to the surface and scatter it so as not to draw attention to the entrance.
Then they begin digging parallel to the surface before terminating the tunnel in a sleeping chamber. Burrows can have more than one entrance and be over 20 feet long.
The following description of the interior of the burrow is indebted to naturenotesblog.
“A chipmunk's burrow is made up of several tunnels, pockets, and chambers. There are several entrances, typically camouflaged under rocks and bushes. These allow for a quick escape from a predator (such as a snake), a tunnel collapse, or a flooding situation. 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.”
Foraging and Diet
Chipmunks are diurnal (active in the daytime) and much of a chipmunk’s day is spent in finding, collecting and storing food. Although most species of chipmunks forage on the ground, they are also capable of climbing trees and shrubs to harvest nuts and fruit. Seeds are its main source of food. One tiny chipmunk can gather up to 165 acorns a day.
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Throughout the spring, summer, and autumn, the chipmunk’s diet is supplemented with nuts, flowers, plant bulbs, berries, cherry and plum pits, mushrooms, insects, worms, snails, frogs and, occasionally, bird eggs and small birds. If chipmunks live in close proximity to humans you may notice chipmunks scampering to eat pet food from outdoor bowls or climbing to steal seeds straight from bird feeders.
Chipmunks can store up to 8 lbs. of food in their burrows; this is referred to as ‘larder hoarding’. In warm weather they also engage in ‘scatter hoarding’, concealing seeds, nuts and other food in shallow little depressions under the cover of leaves and grass or beneath logs.
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A chipmunk spends the winter in its burrow in a state of torpor. Its heart which usually beats 350 times a minute will slow to 4 beats a minute and its body temperature will cool to just above freezing. Rather than accumulating heavy fat reserves, a chipmunk relies on the food it has stored in its burrow and will break its long winter sleep every week or so to eat.
Threats
Chipmunks are mainly threatened by the loss of their natural habitat as a result of encroachment.
In terms of predators, just about any carnivore bigger than one of these little rodents is a potential threat. That includes owls, hawks, weasels, foxes, coyotes, raccoons, bobcats, lynxes, cats, dogs, snakes, and sometimes even their own squirrel cousins. Chipmunks are quick, nimble and vigilant. They often rely on a speedy escape that allows them to disappear into their burrows.
Ecological Significance
Chipmunks are categorized as a species of “least-concern” by the International Union for Conservation of Nature (IUCN). Chipmunks are not a focus of wildlife conservation because the species is considered to have a stable population and to be plentiful in the wild.
Chipmunks play a very important part in their respective ecosystems. On a daily basis, chipmunks gather and transport seeds and nuts and stash them under plant or dirt cover. Many of the “left-over” or forgotten seeds will become seedlings and thus the chipmunk helps support the establishment and spread of various plants.
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They also eat and collect a large variety of fungi and help to spread their spores around. According to wildlifeanimalcontrol.com, “Some fungi, like the truffle, have lost their ability to disperse their spores through the air because of mammals like the chipmunks. These particular fungi have co-existed and co-evolved with these mammals for so long that they only use mammals to disperse and, therefore, reproduce.”
From Animal Fact Files we present this charming little video that will bring you even closer to the charming little chipmunks who share our surroundings at Hotel Lake.
References:
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Hinterland Who’s Who, Chipmunk, https://www.hww.ca/en/wildlife/mammals/chipmunk.html
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Animalia, https://animalia.bio/least-chipmunk
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US National Science Foundation, https://www.nsf.gov/news/mmg/mmg_disp.jsp?med_id=186508
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https://www.procyonwildlife.com/2022/06/29/hail-the-mighty-chipmunk/
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https://www.treehugger.com/things-you-dont-know-about-chipmunks-4864283
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https://naturenotesblog.blogspot.com/2020/08/life-underground-secret-life-of.html​​