OCTOBER 1989 - City of Boulder

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LEAST CHIPMUNK Distribution.--The least chipmunk is a species of the western United States, ranging east to Wisconsin, Nebraska, Colorado, and New Mexico. In central Colorado, this is a species of the 'mountains, and the animals occur throughout much of the Boulder Mountain Park system. Description.--A distinct pattern of four pale stripes and five blackish stripes, and two pale stripes on the face, characterize this animal. It is very difficult to distinguish this species from - E. quadrivittatus or g. umbrinus in the field. Color and size, cranial details, and baculum are often good characters (depending on geographical location) to distinguish museum specimens. Mean (and extreme) measurements of four females from Boulder County we=e: total length, 203.0 (200-208); tail, 86.0 (79-93); hindfoot, 31.7 (31-33) ; ear, 16.3 (15-18); weights range from 35 to 60 gr. Cranial measurements include : greatest length of skull, 32.20 (31.9-32.7) ; zygomatic breadth, 17.60 (17.2-17.9). Natural History.-Least chipmunks are found almost anywhere but wholly open ground including sagebrush, pine and spruce forests, in brush along streams, and areas of brush and rocks. The animals use both ground and tree nests, and also may have underground burrows at the end of a somevhat intricate tunnel system. The chipmunk's peak activity is in the morning, only a few hours are spent above ground each day. There has been disagreement as to whether or not they hibernate during the colder months, but most probably go into torpor and remain underground most of the winter. Occasionally they surface to forage for food or to sun themselves . Food consists of a variety of vegetation, vith dandelions being the preferred source of food in west-central Colorado, and comprising over 80 percent of the diet during the summer. When readily available, fruits, nuts, berries, stems, seeds, and occasional insects are eaten. Females are monoestrous, giving birth to five to eight altricial young. The chipmunk's breeding season is in late spring and early sumuer. By two weeks of age, the young are covered with a pale, silky fur, and the eyes are open. Based on tooth eruption patterns, ages are: juveniles, birth to 60 days; sudadults, 60-90 to 100 days; adult, older than 100 days. Longevity is unknown. Coyotes prey upon chipmunks as do weasels and diu~lal raptors, More study is needed on their ecology, as well as other aspects of their biology. Difficulties in identification have led to neglect of these conspicuous little squirrels. Selected References . --Carleton (1966) ; Telleen (1976, 1978) ; Skryja (1974). B.S.S.
-- 48-- THIRTZEN-LINED GmUND SQUIRREL Spermophilus tridecemlineatus Distribution.--The thirteen-lined ground squirrel ranges from south- central Canada southward to Texas and from the Rocky Mountains to the northern Lake States. They occur throughout eastern Boulder County, extending in suitable habitat to the base of the foothills. Description . -SI_ tridecemlineatus is similar in size to the sympatric spotted ground squirrel. The pelage is moderately bushy with a pattern consisting of a series of alternating brownish or blackish and light longitudinal stripes with a row of almost square white spots in each dark dorsal stripe. Mean (and extreme) external measurements of eight males and of five females from Larimer County are: total length, 244.6 (212-260), 248.6 (228-260) ; tail, 84.2 (78-104), 89.2 (76-98) ; length hindfoot, 32.4 130-35) , 33.2 (31-35) ; weights of five males, 158.30 (125 .O-193.5). Greatest length of skull of seven males, 40 -33 (38.4-41.0), zygomatic breadth, 23.63 (23 -0-24 .I). Natural Eistoqo--The thirteen-lined ground squirrel inhabits dry grasslands ranging from sea level to 2740 m. They prefer short grass such as grazed pastures, golf courses, and' highway borders and commonly are found in farmland. Home ranges of males are approx3mately 11.5 acres, largest during the breeding season. Home ranges of females are approximately 3.5 acres, largest during pregnancy and lactation. These animals are burrowers. Burrow openings are not marked by a mound of soil, Vocalization is a twittering or whistling alarm call, Hibernation is preceeded by weight gain, aggressiveness, a reduction in home range and reduced activity. Males may enter hibernation in July, females in late July and early August, and mose young by early September. Emergence occurs about mid-April, males emerging a week earlier than females. Periodic arousals, occurrirgevery 10-26 days, interrupt hibernation. During summer the animals are diusnal and mostly solitary. Diet consists of insects and larvae, grass, seeds, and flower and fruit heads in srmrmer, In Colorado, mating occurs the first two weeks after emergence. After a 284ay gestation period, females bear an average of eight to ten young. The young are weaned at 28 days and reach reproductive capacity at rrine months. Females bear one litter annually. survivorship of young is 16 percent compared to 29 percent for adults. Longevity is 4 to 5 years. Badgers, coyotes, skunks, foxes, weasels, hawks, and snakes are known to prey on these squirrels, which are beneficial economically due to their insect consumption and soil-building. Bovever, they are also injurious to crops such as peas, beans, cucumbers, squash, wheat, and oats. Selected References .-McCartey (1966) ; Streubel and Fitzgerald (1978b) . 1
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ROY E. DAWSON SEASONAL PARK RANGER
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historical (Simpson 1965). The obje
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qauru Ao 1 IeA lap Inog suo K qeao
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Figure = 4 Trrnsect locations 111 1
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Table 1. Selected study habitats (A
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ats and extirpated species from the
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Table 3 Site and Transect Locations
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faunal elements are represented by
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Onvchomv. Nwthwn Grasshopper House
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8 House House Order ~arni vora Carn
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t mnis Jatrans Coyote Canis JUDW 6r
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ermwhi lus ) rtcrrl i s 601 den-man
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.Order Insectivwa panus Dwarf Shrew
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Order Insectivora WNDEROSA PINE cin
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individuals were caught in pitf a1
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REFERENCES Armstrong, Dm PI. 1972.
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Order Marsupi carnivora I POTENTIAL
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t h r m ncarl oti; Uestern Harvest
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SPECIES ACCOUNTS OF OBSERVED &NI MA
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FIGURE 2. Skull and jaw of Zapw hud
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0 a douthitti, to be more abundant
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and 22 October, 1 November (2), and
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CryptOtis parva. By John 0. Whitder
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MAM!tIALIAN SI'ECIES NO. 43 abscnt.
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MAMMALIAN SPECIES NO. 43 and Wharto
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MAMMALIAN SPECIES NO. 43 7 Dryden,
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MAMMALIAN SPECIES No.'56. pp. 1-3.
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MAMMALIAN SPECIES NO. 56 / Known he
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2 MAMMALIAN SPECIES 79 LUPUS pambas
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a &=station 4 MAMMALIAN SPECIES 79
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itt~riality). In Arkanras. Gipson a
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a Horn. of facial expressions in ca
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Spermophilus tridecemlineatus. By D
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MAMMALIAN SPECIES 103 3 ing emergen
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MAMMALIAN SPECIES 103 5 ground squi
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2 FIGURE 1. Skull of Sylvilagus aud
Page 74 and 75: LITERATURE CITED Allen, J. A. 1877.
Page 76 and 77: FIGURE 2. Skull and mandible of Syl
Page 78 and 79: 4 MAMMALIAN SPECIES 136 1939). The
Page 80 and 81: - 1904. Mammals from Southern Mexic
Page 82 and 83: a Pelton, 8 MAMMALIAN SPECIES 136 -
Page 84 and 85: 2 MAMMALIAN SPECIES 159 FIGURE 1. D
Page 86 and 87: a and a dent 4 MAMMALIAN SPECIES 15
Page 88 and 89: Q f Microtus prnnsvlvanicus) as a l
Page 90 and 91: 5 8 MAMMALIAN SPECIES 159 ! eters o
Page 92 and 93: 2 MAMMALIAN SPECIES 167 FIGURE 2. D
Page 94 and 95: MAMMALIAN SPECIES 167 Coulombe. H.
Page 96 and 97: Odocoileus hemionus. 'B~ Allen E. A
Page 98 and 99: MAMMALIAN SPECIES 219 responsible f
Page 100 and 101: MAMMALIAN SPECIES 219 captive 0. h.
Page 102 and 103: MAMMALIAN SPECIES 219 Anderson. A.
Page 105 and 106: Neotoma mexicana. e, John E. Comely
Page 107 and 108: MAMMALIAN SPECIES 262 The baculum o
Page 109 and 110: MAMMALIAN SPECIES 262 during severa
Page 111 and 112: MAMMALIAN SPECIES 262 MURRAY. K. F.
Page 113 and 114: L 10 mrn FIG. 2. Dorsal, ventral, a
Page 115 and 116: 4 MAMMALIAN SPECIES 272 the facial
Page 117 and 118: direction of the danger stimulus; w
Page 119 and 120: 8 MAMMALIAN SPECIES 272 LAYNE. J. N
Page 121 and 122: EASTERN COTTONTAIL -Sy lvilaws f lo
Page 123: --39- DESERT COTTONTAIL Sylvilagus
Page 127 and 128: BLACK-TAILED PRAIRIE DOG Cynomys lu
Page 129 and 130: Thomomy s talpoides Distribution.-T
Page 131 and 132: WESTERN EARVEST MOUSE 'Reithrodonto
Page 133 and 134: --69-- MEXICAN WOODRAT ~istribution
Page 135 and 136: -- 76- PRAIRIE VOLE Microtus ochrog
Page 137 and 138: COYOTE Canis latrans ~istributian--
Page 139 and 140: Odocoileus hemionus Distribution--T
Page 141 and 142: Common Name Scientific Name Habitat
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OCTOBER 1989 - City of Boulder

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