Eastern Chipmunks (Tamias striatus)
Ontario, Canada

There are many different species (types) of chipmunks in North America. Although more research is needed, some scientists think there may be as many as 20 different species in North America.

Chipmunks Tamias are fun to watch. Found throughout Ontario's forests, they charm campers and hikers by their small size, their boldness in search of food, and their constant busyness. They are not hard to approach or photograph. An encounter with a chipmunk often provides a child with a captivating first experience of a wild mammal in its natural setting.

In Ontario there are two main types of chipmunk. One is known as the eastern chipmunk. The second is known as the least chipmunk. These chipmunks are very similar in appearance and behaviour. The eastern chipmunk is larger and is located mostly in the eastern part of Canada. The least chipmunk is smaller but has a much larger range. It is found in Ontario, across the Prairies, and into the province of British Columbia.

The eastern chipmunk is a member of the squirrel family which means it is also a rodent. The name of the chipmunk in Latin means 'striped storer'. This comes from the fact the chipmunk has stripes on its back and much of its life is centred on the storage of food.

Appearance

Chipmunks are easily recognized by the light and dark stripes on the back and head. They can be confused with some of the striped ground squirrels, but chipmunks are smaller, bear facial markings, and have five dark stripes on their backs, including a distinct, central line that extends forward onto the head. Ground squirrels do not have markings on the head.

The eastern chipmunk is a colourful and attractive rodent with bright russet on its hips, rump, and tail; black, grey, and white stripes on its back; brown, grey, and buff on its head; white underparts; and brown feet.

The eastern chipmunk is large (up to 125g) with a relatively short tail (about one-third of the total length from its nose to the tip of its tail). The eastern chipmunk is between 20 and 33cm long, and western species are 16 to 28cm long.

Habitat/Behavior

The chipmunk lives in a variety of habitats. It likes living in hardwood forests that contain many of the trees that produce the nuts it likes to eat. It also lives in valleys where there are shrubs and rocks.

Most chipmunks live in burrows and gather food on the ground, generally in areas where there are enough rocks, bushes, fallen logs, and piles of brush to shelter them from predators as they scamper about. Immature forests and the edges of forests near clearings, streams, ravines, and logging roads provide ample cover. Stands of tall, mature trees with no plants on the shady forest floor are unsuitable.

Chipmunks can also be found living in city parks where there are trees and in areas where it can find protection from the wind and rain.

The chipmunk hibernates in winter but doesn't build up layers of fat like the woodchuck. It awakens during the winter to feed on its stored food.

Chipmunks are quite vocal. People walking in the woods do not always realize that they are hearing chipmunks, for some of the cries that chipmunks make are like bird chirps.

Biologists have not yet determined the meaning of all the chipmunk's many calls. For example, when a chipmunk is startled, it runs quickly along the ground giving a rapid series of loud chips and squeaks. Perhaps this sudden burst of noise startles predators, helping the chipmunk to escape. Also, chipmunks frequently call with a high-pitched "chip" or "chuck" repeated over and over at intervals of one or two seconds. This scolding noise is often made by a chipmunk watching an intruder from a safe vantage point. Some scientists think that it may also be the mating call of the female chipmunk.

Surprisingly, in animals so quick to befriend curious children and captivate their jaded elders, chipmunks are solitary animals.

Burrows

Most chipmunks construct tunnels and chambers in the ground that have entrances that are well hidden under rocks or tangled bushes. Less typical are those western species that spend a fair amount of their time in trees and sometimes even nest in tree cavities.

Each chipmunk has its own burrow and ignores its fellows except when conflicts arise or during mating or when females care for their young.

The chipmunk's home is an underground burrow. The burrow provides protection from the cold and also from the heat on hot summer days. It provides protection from enemies and it is also used to store nuts for the winter.

The chipmunk starts the burrow by digging a hole about 25 to 70 cm deep. The chipmunk then digs a chamber (room) about 15 cm high and about 30 cm in diameter. The bottom of the chamber is lined with shredded materials like leaves and grasses. This main area is used for hibernating, resting, giving birth and also food storage. Additional rooms are sometimes built to store food.

When digging a tunnel, the chipmunk uses its teeth to cut roots from trees and shrubs. It uses its front and rear feet to push the dirt behind its body. It then turns around and pushes the dirt out, using its head and nose like a bulldozer. The first tunnel is called a working tunnel because it is not the main entrance. The chipmunk doesn't want its main entrance to be surrounded by dirt and debris. This would make it easy for its enemies to find its home. In order to keep the main entrance free of dirt, the chipmunk builds a tunnel from the inside of the chamber. This tunnel goes to the surface of the ground. This main entrance may be seven or eight metres from the entrance to the working tunnel.

It is important to understand that each chipmunk's home is special. Some may have two or three chambers instead of just one. Some may have many tunnels leading up to the ground level. The chipmunk also spends time changing its burrow. It may change the main entrance from time to time and also build additional chambers for the storage of food. The chipmunk usually has only one main entrance to its home. If it builds a new entrance, the old one is blocked with dirt. The chipmunk has also been known to block the main entrance at night before going to sleep. In the morning it simply removes the dirt and goes to work gathering nuts.

Food

A chipmunk spends much of its day collecting and storing seeds, which are its most important source of food. Although most species of chipmunks most often forage on the ground, they all easily climb trees and shrubs to harvest nuts and fruit.

When preparing food for storage, the chipmunk holds fruit and seeds in its dexterous front paws, and with specialized incisors, which are especially long and directed forward, it removes seeds from pods. Then it uses its tongue to shift them backwards and stuff them between its teeth and the extensible skin in the cheek area, where they are held while the animal collects more food. The capacity of these cheek pouches increases with maturity. When the cheek pouches become full, the chipmunk deposits the seeds in its nest or buries them in shallow holes that it digs in the ground and then covers with earth, leaves, and other litter.

In spring, chipmunks diligently search the ground for any seeds that remain from the previous summer. As these are usually scarce, the small rodents eat young leaves and shoots until new fruit and seeds become available. Throughout the spring, summer, and autumn, the chipmunk's diet is supplemented with insects, earthworms, flowers, berries, cherry and plum pits, mushrooms, and occasionally eggs or carrion. Rare instances of chipmunks preying on birds or small mammals have been observed.

Chipmunks are active during the day and sleep in their underground burrows at night. The chipmunk is an alert, fast-moving animal. It spends much of its time hunting for food. The food is gathered in cheek pouches. These cheek pouches are like little shopping bags and are used to carry food to the underground burrow. In researching the chipmunk, scientists have found that it can carry over 50 watermelon seeds in these pouches. The chipmunks eat a wide variety of foods, including acorns, chestnuts, hickory nuts, mushrooms, insects, fruit, and berries.

Range/Territory

No species of chipmunk is found north of the treeline in Canada, in the prairie grasslands of North America, in the hot subtropical forests of Florida, or in areas with waterlogged soils. With those exceptions, chipmunks thrive throughout Canada and the United States. Some species of chipmunks even occur above the timber line on mountains and in the semidesert regions of the western United States. Their range extends south into Mexico along the mountains.

Chipmunks spend most of their time in the part of their home range that includes their burrow, which is called their dominance area. Between these smaller dominance areas there is no overlap. The chipmunks defend the dominance area that is near the entrance to its burrow. If another chipmunk comes near the entrance it chases it away. By chasing away others, it can protect its underground collection of food from being stolen. The boundaries of dominance areas are more stable than those of home ranges.

The home ranges of chipmunks are overlapping . This means that they share parts of their home range or territory with other chipmunks. The home range is quite small, and most chipmunks don't travel more than 15 metres from their homes. Home ranges vary from 0.04 to 1.26ha; usually those of adults are larger than those of juveniles and those of males larger than those of females. Boundaries change continually to include seasonally available food sources, but most animals probably maintain approximately the same home range from season to season.

Hibernation

Chipmunks are known to be hibernators, even in the southern parts of their range. Near the end of July, they begin to collect and store large quantities of seeds. By October, each chipmunk has accumulated enough seeds to enable it to survive the winter.

With the onset of winter in November, chipmunks disappear below ground. At present, it is not known exactly what happens when chipmunks retire to their burrows for the winter. One view is that they immediately go into a torpid state. (In this state, the body temperature, rate of breathing, and rate of heartbeat drop to very low levels, reducing the amount of energy required to maintain the chipmunk.) Periods of torpor last from one to eight days, and perhaps longer. Between periods of torpor, chipmunks wake up and consume part of their food supply. They have occasionally been seen above ground on warm winter days. A second view of chipmunk hibernation is that chipmunks do not actually hibernate until their food supply has been exhausted.

With the first warm days of March, chipmunks begin to emerge, sometime burrowing up through a metre of snow.

Breeding Biology

Male chipmunks are the first to emerge in the spring, as soon as patches of bare ground begin to appear through the snow. The females emerge one or two weeks later, and soon after, breeding takes place near the female's burrow. Several males may compete for a female and a male may mate with more than one female during one breeding season. In Canada, the main breeding season is from mid-April to mid-May.

In Ontario, chipmunks usually mate in April or May. The males come out from their underground burrows where they have been hibernating, and begin looking for females. The females emerge one or two weeks later, and soon after, breeding takes place near the female's burrow. The females are usually chased by a number of males who want to mate. The males follow the females in a line and fight among themselves to see who can get closest to them. If the female chipmunks are not ready for mating they can be quite aggressive and will turn and chase the males away. They sometimes attack the males who are following too closely. The females eventually become receptive (ready to mate). Usually the strongest, most dominant male chipmunks get to mate with the females.

Mating lasts for about one or two minutes, and then the females and males stay together for a short time. The females then chase the males away. After a gestation period of about 31 days, the young chipmunks are born. During this time, the females carry leaves and grasses to their underground dens. The underground home has a large room or chamber that is used as a nesting site.

The gestation period is about 30 days. When it is over, the female chipmunks rear their litters (usually four to six young) without any help from males. In Canada, in most years, chipmunks have only one breeding season and one litter, but in favourable years a small percentage of adult eastern chipmunks produces a second litter in the fall. In the southern United States, the production of two litters per year by both eastern and western chipmunks is not uncommon.

At birth, the baby chipmunks are pink, hairless, are about six cm long and weigh about 3g at birth, which is the same as about three paper clips, with some variation by species. In the eastern chipmunk, hair does not become visible to the unaided eye until about 10 days of age, the ears are closed until around the 28th day, and the eyes open at 31-33 days of age.

By the age of three weeks, the young are fully furred and by the time they are five to seven weeks old, the young chipmunks begin to leave the burrow to forage. When the baby chipmunks first come out of their den, they explore the ground near the entrance. At first they are unafraid, but after a few days above ground they are more wary and escape quickly if disturbed. Their mothers keep a close watch on them. The young grow rapidly during the late summer and reach adult size before the end of September. The mothers and the babies remain together for about three months and then begin to separate. Most breed in their first spring, but some may wait until their second year.

The time of separation is difficult for the young chipmunks. The young must quickly find new homes. Most of the young try to find empty burrows close to where they were born. The other chipmunks in the area make a chip-chip-chip sound. This lets the young know which areas or territories are already taken. Some of the young must travel to new areas to locate a home.

Predators/Threats/Lifespan

Like most small rodents, this chipmunk is subjected to heavy predation. In the boreal forest it is hunted by hawks, owls, ermine, mink, marten and fishers. In suburban environments, it often falls prey to cats and dogs and a fair number are killed by automobiles.

Despite these many enemies, there are not enough of these tiny rodents for any predator to depend on a steady diet of chipmunk. It makes more sense for a predator to specialize in mice, which are more abundant and more easily caught.

However, its numbers are high. A female will produce a litter of 2 to 7 offspring each year.

Chipmunk numbers usually do not vary much from year to year, but local declines and disappearances have been recorded. These declines have never been satisfactorily explained.

Chipmunks can be seriously wounded when they compete among themselves or with large animals such as red squirrels for food and space. In addition, some may die as a result of wounds received in fights during the breeding season. Males fight among themselves when competing for females, and females have been observed defending their nests and young against other chipmunks.

Disease and food shortage may also limit chipmunk populations but, once again, little is known about these factors. Seed crop failures are likely to have a significant detrimental effect on chipmunks, which depend on stored food to survive the winter. Disease epidemics have not been reported from chipmunks, but are known to occur in populations of mice and other rodents. Parasites, such as botfly larvae, tapeworms, fleas, mites, and probably lice, can have a debilitating effect and, on rare occasions, even cause death.

In the wild, the chipmunk's life span is from two to five years.

Chipmunks and People

Chipmunks are important in the dispersal of seeds because of their habit of storing them beneath the layer of decaying vegetation on the forest floor. Any buried seeds that are not consumed stand a better chance of germinating than those remaining on the surface litter. In this way, chipmunks assist in the spread of shrubs, trees, and other plants.

If chipmunks are very abundant, they can prevent normal reforestation of some trees, especially pines, by eating their seeds. Occasionally chipmunks and other rodents are trapped to ensure adequate germination and growth of seedlings. Poisoning is not an acceptable means of control because of the harmful effects on other wildlife including gamebirds and songbirds.

Much of the value of chipmunks lies in the pleasure they provide for campers, hikers, and anyone who enjoys the country. Our national and provincial parks and our summer cottages and trailers would be less interesting and less enjoyable without chipmunks dashing across forest trails or boldly helping themselves to food in campgrounds and picnic areas.

Other Species of chipmunk

Twenty-one chipmunk species occur in North America, including one in eastern Canada and four in western Canada. All these species belong to the genus Tamias, which is divided into two main groups. The first subgenus, also called Tamias, contains the eastern chipmunk T. striatus, found in eastern Canada and the eastern United States. (It also contains the only species of chipmunk from outside North America, T. sibericus of China.) The other subgenus, Neotamias, contains 20 species, all of which are native to western North America. Four Neotamias species are found in western Canada. The least chipmunk T. minimus is the most common and has the largest range, followed by the yellow-pine chipmunk T. amoenus and the red-tailed chipmunk T. ruficaudus; the Townsend's chipmunk T. townsendiii is found in Canada only in the extreme southwestern corner of British Columbia.

Track

Chipmunks are so light that their prints rarely show details. Forefoot has four toes, hind foot has five. These chipmunks run on their toes, therfore the forefoot pads do not show, the hind feet have no pads. Hind prints register ahead of the fore prints and tracks are erratic. Trails usually lead to a burrow.

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