Eastern chipmunk
| Eastern chipmunk | |
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| Genus: | Tamias Illiger, 1811
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| Species: | T. striatus
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| Binomial name | |
| Tamias striatus Linnaeus, 1758
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The eastern chipmunk (Tamias striatus) is a small, striped rodent found in North American woodlands. A member of the squirrel family, it is the only living member of the genus Tamias, one of three genera of chipmunks. Its distribution extends from southern Canada in the north to Louisiana and the Florida panhandle in the south, and from the middle United States in the west to Virginia and the western mountains of the Carolinas in the east.
The eastern chipmunk is solitary (except during its mating season), diurnal, and lives in a burrow of extensive tunnels, well-hidden entrances, and chambers for sleeping, nesting, and storing large quantities of food. In winter, the chipmunk retires to the burrow, enters a state of torpor, but wakens frequently to move about underground or to eat from its stores. It vocalizes with bird-like chirps, chips, chucks, and squeaks. Predators include hawks, foxes, and weasels.
The eastern chipmunk is omnivorous, and its diet includes nuts, seeds, and fruits as well as insects. The breeding season occurs annually in the middle spring, or biannually in early spring and again in middle summer, depending on the geographic region. Gestation is 30–32 days, and the young leave the nest at about seven weeks. The species is infected by internal and external parasites including a host-specific louse and a mite that damages the end of the tail. In the wild, lifespan is one to three years, and in captivity, about nine years.
The species is of no economic value to humans, poses little or no threat to crops or other human interests, and is of least concern to conservationists because it is abundant, widespread, and faces no major threats. The eastern chipmunk is a bustling little animal which provides amusement for human onlookers.
Taxonomy
In 1886, zoologist Clinton Hart Merriam traced the first mention of the eastern chipmunk in western literature to the fifth volume (p. 746) of French missionary Gabriel Sagard's L'histoire du Canada published in 1615.[3] In 1743, Mark Catesby named the species Sciurus striatus (Greek: striped scourer) in the second volume (p. 75) of The Natural History of Carolina, Florida and the Bahamas:
Sciurus striatus. The Ground Squirrel. This is about half the Size of the English Squirrel, and almost of the same Colour, except that a Pair of black Lists, with a yellowish white List between them, extend almost the Length of the Body on both sides; also a single black List runs along the Ridge of the Back. The Eyes are black and large, the Ears rounding, the Tail long, flat, and thick set with Hairs, which are much shorter than those of other squirrels. These squirrels abide in the Woods of Carolina, Virginia, &c. Their Food is Nuts, Acorns, and such like as other Squirrels feed on. They being brought up tame, are very familiar and active.[3]
In 1758, Linnaeus adopted the name Sciurus striatus for the species in the tenth edition of his Systema Naturae.[3] In 1811, it was reclassified Tamias striatus (striped steward) by Johann Illiger.[4] The specific name striatus experienced some vicissitudes over the years but was reestablished by Baird in 1857.[3]
The eastern chipmunk is often classified with all the other chipmunks in a genus Tamias. Some taxonomists, such as Arthur H. Howell in 1929 and John A. White in 1953, have assigned the eastern chipmunk to the genus Tamias and all other chipmunks to the genus Eutamias, based on the number of teeth. In 1940, J. R. Ellerman assigned the genus Tamias to all chipmunks regardless of the number of teeth but allowed three subgenera, Tamias, Eutamias, and Neotamias, based on geographic ranges.[4] Some taxonomists classify each of Ellerman's subgenera as distinct genera, since each chipmunk group is as distinct as other genera of ground squirrels are from each other.[5][6] The Pleistocene fossil Tamias aristus from Georgia is closely related to the eastern chipmunk and placed with it in the genus Tamias.[7]
Description
The eastern chipmunk is a small, moderately heavy-set squirrel displaying several prominent longitudinal stripes and an overall grayish to reddish-brown coloration.[8] More specifically, the species is colored white to buff to rust to brown with a yellow-brown head, clay-colored cheeks,[9] white facial stripes bordered by darker stripes running longitudinally above and below the eye,[8] small, rounded but prominent ears,[9] and well-developed expandable cheek pouches for transporting excavated earth away from the burrow or transporting foraged food for winter consumption to the burrow.[9] The feet are buff and the sides rust; the belly is white to buff and the rump rust or brown; the blackish, well-haired but not bushy dorsoventrally flattened tail is peppered with grey above and rust below.[8][9]
Five narrow black stripes, two broader gray stripes (their hairs barred with brown), and two narrow light stripes run longitudinally along the back. One narrow, black stripe runs mid-dorsally along the spine from the back of the head before fading into the rump. The four other black stripes run parallel to the mid-dorsal stripe and border the two light stripes.[9]
The darkest individuals are found in Kentucky, Tennessee, and the mountains of the Carolinas while the smallest and lightest are found in the northeastern United States. Albinos and melanists have been noted. Coloration varies considerably over its range, but individuals in specific localities display little variation.[8][9]
The eastern chipmunk has four toes on its forefeet, five toes on its hindfeet, four pairs of mammae, and differs from chipmunks in the genera Eutamias and Neotamias by the absence of the third upper premolar, by the width of some stripes, by keel on the ventral tip of the penis bone, the structure of some bones, and a relatively shorter tail.[8]
Specimens from Indiana averaged 242 mm (9.5 in) 183–275 mm (7.2–10.8 in) in total length; 86 mm (3.4 in) 68–111 mm (2.7–4.4 in) in tail length; 34 mm (1.3 in) 28–44 mm (1.1–1.7 in) in hind foot length; and weighed 111 g (3.9 oz) 90–149 g (3.2–5.3 oz).[9]
The eastern chipmunk has 38 chromosomes (2n = 38). The tooth formula is 1.0.1.31.0.1.3 × 2 = 20 (one incisor, one premolar, and three molars on each side of both the upper and lower jaws).[9]
Distribution and habitat
The eastern chipmunk is both an urban and wilderness dweller.[8] It is native to North America and is widely distributed throughout the eastern United States from Wisconsin and Maine in the north to Louisiana, Alabama, northern Georgia, and the Florida panhandle in the south, and from the middle United States in the west to coastal Virginia and the westernmost reaches of North and South Carolina in the east.[9] It is not found in peninsular Florida nor the coastal plain between Florida and northern North Carolina.[1] In Canada, the species is found from southeast Saskatchewan in the west to Nova Scotia in the east, and was introduced at three sites in Newfoundland in the 1960s.[1][8][9]
Eastern chipmunks live in temperate, open, deciduous forests and woods with ample ground cover. In the Adirondacks of New York State, the species occurs at elevations to 4000 ft (1220 m) in deciduous and mixed forests, and is most abundant in mature hardwood forest situations of sugar maple, beech, and a fairly open understory.[10] The chipmunk prefers the edges of oak and hickory or beech and maple forests but is equally at home in hedge and fence rows, under stone walls and piles of rotting logs, in tangled bush and shrub, and in rural or urban gardens.[1][9][11] They have been observed making their burrows in mowed lawns.[9]
Behavior
Home ranges
The home range of the eastern chipmunk is about 1.0 acre (0.4 ha) for males, 0.5 acres (0.2 ha) for females, and 0.2 acres (0.08 ha) for both male and female juveniles. A chipmunk's home range may overlap those of others, and, as fruits, nuts, and seeds ripen or population density changes, an individual's home range may shift accordingly.[12] The home range is usually permanent. The young may travel great distances before settling, but once an adult female has settled, she rarely relocates, and males relocate only short distances during the mating seasons.[12] A chipmunk may be required to return quickly to the burrow or to protect the burrow's food stores, and therefore its time outside the burrow is dependent upon nearness to the burrow.[13]
Home ranges are usually largest in early summer and early autumn. Breeding males have the largest ranges. Small areas surrounding the burrow are defended against incursions from conspecific neighbors, and an individual may expand its range if water becomes scarce.[1] Settled individuals have about a quarter mile lifetime home range length while dispersing individuals may venture as far as a half mile.[1] Two and a half acres (one hectare) may be home for about 38 chipmunks, but population may vary considerably from one year to the next.[14]
Burrowing
Eastern chipmunks build extensive underground burrow systems of tunnels and chambers. A chipmunk may use its forefeet to excavate part of the burrow and its cheek pouches to carry the excavated earth away from the burrow site, but renovation of old burrows or the burrows of other mammals is the primary method of burrow building. Pre-existing tunnels and burrows may be a requirement for establishing a home range. Some tunnels may be dug deeply into the earth to manage flooding.[10]
Burrow openings are found near rocks, tree bases, or under the edge of a building.[1] These openings individually measure 40–60 mm (1.6–2.4 in) in diameter, and are numerous along woodland banks, but difficult to see because the excavated earth is carried away and dispersed rather than piled at the burrow's entrance in the manner of other burrowing mammals.[9]
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Two types of burrow are noted: a single-chambered structure with one or two tunnels, and a more extensive burrow of several chambers, several tunnels, and many entrances. The single-chambered burrow may be constructed as a temporary refuge, or built by young chipmunks for shelter through their first year. Adult males typically live in such simple burrows. Large burrows may have as many as five openings. One burrow was studied with thirty openings but only five openings were in use. A burrow system may have 30 m (100 ft) of tunnels.[13] The nesting chamber measures approximately 60 by 40 by 25 centimeters (24 by 15 by 10 inches) and is lined with whole or shredded leaves in which the inhabitant sleeps or bears the young.[15]
As many as three storage chambers (approximately half the size of the nesting chamber) are part of a large burrow. Smaller chambers and side pockets may exist. The burrow descends sharply for several centimeters, then levels off, and extends beyond about 10 m (30 ft). In the northern United States, a burrow may lie 60–74 cm (24–29 in) below the ground surface, but a burrow in the southern states may lie at a much shallower depth. Burrows are more numerous in areas with sparse ground cover.[15]
Diet
Seeds, fruits, nuts, some mushrooms, and insects comprise the diet.[1] Mast composed over 60% of the food volume in 59 chipmunks examined in Indiana prior to 1998. This mast was followed in descending order of volume by various insects (13%), fruits (8.3%), seeds (6.4%), and vertebrates (4.3%). Spores of the subterranean fungus, Endogone, and other fungi were found.[16]
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In spring, shadberries are eaten and, in summer, blackberries and raspberries. Cicadas may be eaten in great quantities in years of high emergence. White oak acorns are preferred to red oak acorns (perhaps because they are smaller and are lower in tannin content), and beechnuts and hickory nuts are consumed. Chipmunks will drink available water, but, in its absence, apparently survive on dew, rain water, and the moisture in their food.[16]
Chipmunks are relatively inactive in July and early August, but, in late summer and early autumn, they become quite busy gathering food for winter use. In 1982, one female chipmunk was observed carrying six white oak acorns in her mouth and cheek pouches to her burrow 30 m (100 ft) distant from the food source. Her round trip required two minutes, and, at that rate, she was moving 116 acorns per hour to her burrow. In a large burrow excavated in 1974 by K. R. Thomas, one storage chamber held 308 acorns and 1 hickory nut (the cache weighing in at 346 grams or 12.2 oz) and the second storage chamber held 82 acorns and 1 hickory nut (weighing 227 g or 8.0 oz).[16] A burrow may contain as much as half a bushel of food but is usually less.[15] John James Audubon once uncovered a large burrow and noted its several chambers contained a gill (120 mL) of mixed wheat and buckwheat seeds, one U.S. dry quart (1.1 L) of hazelnuts, two quarts (2.2 L) of unmixed buckwheat seeds, and eight quarts (¼ bushel, 9 L) of acorns.[17]
Cleanliness and grooming
The eastern chipmunk is a clean animal and engages in grooming not only for the sake of cleanliness but as a displacement activity in times of social stress. The animal can reach all parts of its body with either the paws or the mouth. Washing behind the ears is accomplished by licking the paws and wrist and passing them over and around the ears. The tail is cleaned by passing it through the space between the incisors and the single set of premolars and over the tongue. As a result of attention to grooming and cleanliness, the species is relatively free of parasites.[18]
Hibernation
In the far north, eastern chipmunks retreat to their burrows in October to enter a state of torpor for a period of time. They reappear in mid-March. In the deep south, they retire in December and reappear in late-January.[19] They wake often during the torpid period to move about underground and eat from their stores.[1] A mild spell in December or January may bring some to the surface.[15]
Laboratory studies have shown chipmunks remain torpid for only three to six days and then rouse themselves to engage in their normal physiological functions though they may not leave the burrow. Active chipmunks are more likely to survive the winter. The waking-sleeping cycle may indicate the adaptation to true hibernation is not complete in the chipmunk.[20]
Temperature-sensitive radio transmitters however have confirmed that the eastern chipmunk is a true hibernator. Respiration rates fall from 60 breaths per minute in the active state to 20 in the torpid state, and body temperature drops from 96 to 106 °F (35 to 41 °C) to 42 to 45 °F (5 to 7 °C). It is not known what stimulates hibernation.[15]
Communication and perception
Eastern chipmunks vocalize with bird-like chirps, chucks, squeaks, and chips. A chipmunk in a safe vantage place may scold an intruder repeatedly with a high-pitched chip or chuck at intervals of 1 or 2 seconds, but this call may also be a mating call from the female. Its meaning has not yet been precisely determined by naturalists. A startled chipmunk runs quickly along the ground emitting a rapid series of loud chips and squeaks which may sufficiently distract a predator to enable the chipmunk to reach safety.[13]
Where these chipmunks are numerous in the north, its "chuck" (a downward sweep of 3 to 1 kHz) can be heard well into middle autumn. A startled chipmunk will whistle as it scurries away and males will whistle during the mating chase. Other calls are the high "chip" (a downward sweep of 10 to 3 kHz), the trill of "chips", and the low pitched "cuk". A high-pitched "chip" may be uttered for 130 times per minute for as long as ten minutes. Repetition of calls apparently depends upon the individual's state of excitement. Calls are likely used for alarms and to indicate territories.[13]
Reproduction
Eastern chipmunks pass solitary lives, except during their mating seasons. In the eastern and southern United States, the first mating season occurs between February and April, and the second season between June and August.[14] The second season may involve the young from the previous year.[1] Eastern chipmunks in the north may experience only one mating season.[14]
Females are sexually mature at 187 days and males at 228 days.[21] In late February or March, the testes become scrotal and the males leave their burrows. The females leave their burrows about two weeks later and enter estrus within a few days.[20] Males are above ground at this time, and find their mates by exploring their territories and even entering their burrows.[14] Should one male encounter another, ritualistc wrestling matches occur until one participant retreats.[20] Males ready to mate will gather on the territory of a female in heat and flick the tail up and down, the only time this behavior occurs. If the female is not ready to mate, she will drive the male away.[14]
Mating is often preceded by a chase accompanied by squealing, growling, and chattering, but the female may elude the male and he is then forced to seek a high vantage point to search for her. The dominant male will mate with the female, but if a large number of males are present, he may busy himself driving them away and thus lose the opportunity to mate. The female may then mate with others.[14] Copulation lasts one to two minutes. The male thrusts rapidly while holding the female's hips with his forepaws. She remains stationary. No sounds are emitted. After the act, the two may spend as much as two hours together grooming and eating before the female chases the male away. She mates only once.[22]
Females are in estrus from 3–10 days, but are only receptive for about 6.5 hours.[14] Gestation averages 31 days. During the gestation period, the female excavates her burrow and furnishes the nest. She ingests more protein and retreats to the nest one day to one week before giving birth. Litters usually number 4–5 young weighing on average 3.4 g (0.12 oz). The young are altricial, and parental care falls upon the mother. The body length at birth is 66 mm (2.6 in), the tail 12 mm (0.47 in), and the hindfoot 7.5 mm (0.30 in). At one week, the hair and stripes are visible, and at 28 days the ears open. At one month, the young are 140 mm (5.5 in) long, weigh 30 g (1.1 oz) and the eyes are open.[14] They are weaned at 36 days weighing 50.5 g (1.78 oz).[21] The young emerge from the burrow at about 40 days with approximately 70% of their full growth. They linger near the burrow for a few days, learning to navigate, climb, and defend themselves. At six to eighteen days, the mother denies her young access to the burrow and the young disperse. The entire adult population will join in a general vocalization at this time warning the young of the population density and how far they must travel to establish their own burrows. A few may settle 50 ft (15 m) or so from the mother's burrow. Others may move into abandoned burrows or dig their own. They are persecuted by the adult population and some young may still be wandering and burying small hoards of food by the end of July.[23] Adult weight is 96 g (3.4 oz),[21] and adult dentition is attained at 3 months. The young do not breed in the year of their birth.[14]
Survival
Predators include large snakes, foxes, bobcats, hawks, raccoons, weasels, house cats, and dogs. Weasels will pursue the chipmunk into the innermost recesses of the burrow.[14] In 1907, a "large frog" was seen to capture and eat a chipmunk, and, in 1979, a great blue heron was seen taking chipmunks.[24]
Endoparasites include protozoans, tapeworms, nematodes, trematodes, spiny-headed worms, and the large subcutaneous larvae of botflies, Cuterebra emasculator. Ectoparasites include fleas, ticks, mites, chigger mites, and a host-specific louse, Hoplopleura erratica.[14]
The skin of the eastern chipmunk's tail is naturally fragile, perhaps to thwart predators, and is consequently vulnerable to parasites. The hypopial mite, Aplodontopus sciuricola, lives in the hair follicles of the tail and a large presence of this parasite may be responsible for damaging the skin at the end of the tail or, in some cases, its complete loss.[14]
The expected lifespan of an eastern chipmunk in the wild is perhaps a year or a little over a year; at the extreme, it may live three years in the wild, and has been known to live two to three years. There are records of 13 years in the natural state.[14][25] In captivity, the eastern chipmunk may live eight to nine years. A London zoo specimen of unknown sex lived to be 9 years but may have been older because its birth date was unknown.[1]
Relations with humans
The eastern chipmunk is of no economic value to humans, and poses no threat to crops or other human interests. Its bustling activity provides amusement for human onlookers.[1] [26] The species is widespread and abundant with stable populations; its range includes protected areas, and there are no major threats to its survival. The species is of least concern to conservationists.[1]
Lore, literature, and art
The name 'chipmunk' is assumed to originate in the Native American Adjidaumo (pronounced a-chit'-ä-mauk), through the intermediary form chitmunk. The term means 'head-first' and refers to the red squirrel's manner of descending trees.[4] Henry Wadsworth Longfellow translated the term "tail-in-the-air" in The Song of Hiawatha: "Boys shall call you Adjidaumo / Tail-in-the-air the boys shall call you!"[27]
In the middle nineteenth century, Chamberlain asserted:
There can be no doubt of the Indian origin of this name of the striped ground squirrel (Scuirus striatum), of which many variants, chipmonk, chipmunk, etc. occur. It is derived from atchitamo, the word for "squirrel" in Ojibwa and some closely related dialects [...] Long, in his vocabulary published in 1791, gives the Chippeway (Ojibwa) word for squirrel as chetamon, and by the middle of the present century, the word was current in the English of Canada in the form of chitmunk, which clinches the etymology.
The chipmunk has given his name to several place names in Vernon County, Wisconsin (and elsewhere),[27] and is known colloquially as "grinny" and "ground hackee" in America.[10]
"How the Chipmunk Got His Stripes"[1] is a Native American pourquoi story attributed to the Iroquois. Set in the time when animals could talk, a chipmunk mocks a boastful bear who grows angry under the taunting. As the chipmunk attempts to flee the bear, the bear's claws graze his back and, ever since, the chipmunk has borne a series of scars on his back.
The Tale of Timmy Tiptoes[2] (1911) by English author and illustrator Beatrix Potter tells of Chippy Hackee, an eastern chipmunk, who feeds an eastern grey squirrel so many acorns by that he cannot escape a hollow tree.[28] Potter may have borrowed a pet chipmunk from a cousin as a model for the illustrations,[29] but it is more likely she used photographs and reference materials in the library of the Natural History Museum or viewed the animals in a zoo. The illustrations of the squirrel and chipmunk are considered stiff and unnatural, due perhaps to Potter's unfamiliarity with the animals and her reliance on photographs.[30]
References
- Footnotes
- ^ a b c d e f g h i j k l m Linzey and NatureServe, 2008
- ^ Tamias (striatus) striatus, Mammals Species of the World, 3rd ed.
- ^ a b c d Merriam, 1886, p. 236
- ^ a b c d Wishner, 1982, p. 114
- ^ Musser et al., 2010, p. 22
- ^ Piaggo and Spicer, 2001
- ^ Ray, 1965
- ^ a b c d e f g Snyder, 1982, p. 1
- ^ a b c d e f g h i j k l m Whitaker, 1998, p. 203
- ^ a b c Eastern Chipmunk
- ^ Wishner, 1982, p. 116
- ^ a b Wishner, 1982, p. 115
- ^ a b c d Whitaker, 1998, p. 204
- ^ a b c d e f g h i j k l m Whitaker, 1998, p. 206
- ^ a b c d e Whitaker, 1998, p. 205
- ^ a b c Whitaker, 1998, pp. 205–6
- ^ Marchand, 2000, p. 110
- ^ Wishner, 1982, pp. 115-6
- ^ Wishner, 1982, p. 118
- ^ a b c Wishner, 1982, p. 119
- ^ a b c Tamias striatus
- ^ a b Wishner, 1982, pp. 119–120
- ^ Wishner, 1982, p. 120
- ^ Snyder, 1982, p. 4
- ^ Wishner, 1982, p. 121
- ^ Whitaker, 1998, p. 207
- ^ a b Vogel, 1991, p. 143
- ^ MacDonald, 1986, pp. 75-78
- ^ Hallinan, 2002, p. 82
- ^ Lear, 2007, p. 237
- Works cited
- Hallinan, Camilla (2002), The Ultimate Peter Rabbit: A Visual Guide to the World of Beatrix Potter, New York: DK Publishing Inc., ISBN 0-7894-8538-9
- Eastern Chipmunk, State University of New York College of Environmental Science and Forestry, 2010, retrieved February 1, 2010
- Lear, Linda (2007), Beatrix Potter: A Life in Nature, New York: St. Martin's Griffin, ISBN 0-312-37796-7
- Linzey, A. V. and NatureServe (2008), "Tamias striatus", 2009.2 IUCN Red List of Threatened Species, retrieved January 19, 2010
- MacDonald, Ruth (1986), Beatrix Potter, Boston, MA: Twayne Publishers, ISBN 0-8057-6917-X
- Marchand, Peter J. (2000), Autumn: A Season of Change, Hanover, New Hampshire: University Press of New England, ISBN 0-87451-870-9 (pbk.)
{{citation}}: Check|isbn=value: invalid character (help) - Merriam, C. Hart (1886), "Description of a New Subspecies of the Common Eastern Chipmunk", The American Naturalist, 20, American Society of Naturalists: 236–242
- Musser, G. G.; Durden, L. A.; Holden, M. E.; and Light, J. E. (2010), "Systematic review of endemic Sulawesi squirrels (Rodentia, Sciuridae), with descriptions of new species of associated sucking lice (Insecta, Anoplura), and phylogenetic and zoogeographic assessments of sciurid lice", Bulletin of the American Museum of Natural History (339)
{{citation}}: CS1 maint: multiple names: authors list (link) - Piaggio, Antoinette J. and Greg S. Spicer (2001), "Molecular Phylogeny of the Chipmunks Inferred from Mitochondrial Cytochrome b and Cytochrome Oxidase II Gene Sequences", Molecular Phylogenetics and Evolution, 20 (3): 335–350, doi:10.1006/mpev.2001.0975
- Ray, Clayton E. (1965), "A new chipmunk, Tamias aristus, from the Pleistocene of Georgia", Journal of Paleontology, 39 (5): 1016–1022
- Snyder, Dana P. (May 25, 1982), "Tamias striatus" (PDF), Mammalian Species (168), The American Society of Mammologists: 1–8
- Tamias striatus, Human Ageing Genomic Resources, retrieved January 19, 2010
- Vogel, Virgil J. (1991), Indian Names on Wisconsin's Map, Madison, WI: University of Wisconsin Press, ISBN 0-299-12980-2
- Whitaker, Jr., John O. and William, John Hamilton, Jr. (1998) [1943 (1 ed.), 1979 (2 ed.)], Mammals of the Eastern United States (3 ed.), Ithaca, New York: Cornell University Press, ISBN 0-8014-3475-0 (cloth)
{{citation}}: Check|isbn=value: invalid character (help)CS1 maint: multiple names: authors list (link) - Wishner, Lawrence (1982), Eastern Chipmunks: Secrets of Their Solitary Lives, Washington, DC: Smithsonian Institution Press, ISBN 0-87474-962-X
External links
