OCTOBER 1989 - City of Boulder

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MEAD(KJ VOLE I Micotus penns~lvanicus Distribution--The meadow vole has the most extensive range of any North American microtine, except the muskrat, occuring throughout Canada, the northern and eastern United States, and southward into Mexico. In Colorado, the species occurs in the valley of the South Platte River and in the mountains on the Eastern Slope, eastward on the Platte- Arkansas Divide at least to Ramah. On the Mountain arks, it has been captured at the foot of the First Flatiron and in Skunk Canyon. Description--The meadow vole is a medium-sized, robust-bodied mouse with small eyes and ears and short legs. It is distinguishable from other voles by its larger size and relatively short tail. Its fur is long and soft, the summer pelage being sparser and coarser than winter, and the color varies from gray faintly washed with brown to dark brown, the belly being silvery to slightly buffy or dark gray. The tail is bicolored. Measurements of three males and two females from Larimer County were: total length, 192, 180, 185, 187, 178; tail, 54, 44, 67, 56, 50; hindfoot, 23, 21, 22, 23, 22; ear, 15, --, 13, 15, 14; weight, 73.61, --, 68.49 gr. Condylobasal length ranges from 29.4 to 30.2, zygomatic breadth from 16.3 to 17.7. Natural History--Meadow voles seem to prefer moist grasslands or wetlands, but are occasionally found in orchards or wooded areas with little ground cover. Choice of habitat seems to be related to the presence of sympatric species. The meadow vole is reported to be subordinate to other Microtus species. Voles are inclhed to make. surface runways in dense grass or sedge cover, and may burrow if the soil-is not too waterlogged. They are good swimmers. Spherical nests are constructed of leaves and coarse grasses with softer vegetation as lining, and are usually found on the ground surface. The animals may be active both day or night, depending on temperature and ground cover; they do not hibernate. Meadow voles tend to be solitary, and breeding is promiscuous. Voles are said to eat their own weight in food each day. Diet consists primarily of grasses, &, Panicum, and Muhlenbergia being prominent, but the voles will also eat grain, seeds, bark, roots, fruits, flowers, fungi, and sometimes insects. The animals may store food against thin seasons. Mating in meadow voles occurs throughout the year, with up to 17 litters of one to nine young being born per year. Young are altricial, are weaned about two weeks, and are independent soon after. Females begin reproducing in about a month, and males about two weeks later. This vole is said to have more species of predators than any other North American mammal. Owls, hawks, snakes, weasels, foxes, and most other carnivores will prey on them. Densities of vole populations tend to tun in cycles of two to five years. At high densities, this may cause serious damage, especially in orchards, due to girdling. -- Selected References-Brown (1977), Jones et al.(in press); Reich (1981). S.T.G. .
-- 76- PRAIRIE VOLE Microtus ochrogaster Distribution- Prairie voles are found across central North America from Alberta to Ohio and Oklahoma, and west to the base of the Rocky Mountains. They occur in Colorado along the drainages of the South Platte and Republican rivers, westvard to mesas and grassy canyon bottoms of the lower foothills. Description--The species has a dark grayish to dark brown dorsum with coarse, tawny-tipped hair, giving it a grizzled appearance. The venter is pale and buffy and.the tail is short, distinguishing it from the meadow vole which has a finer pelage, grayer belly, and slightly longer tall. Average and extreme measurements of six miles and of five females from Larimer County were: total length, 175.6 (162-188), 175.2 (168- 182) ; tail, 45.2 (41-53) , 45.0 (41-50) ; hindfoot, 21.5 (20-23), 21.5 (20.22); ear, 12.8 (12-IS), 12.8 (12-14); weights, 60.0 (54-71), 59,2 (58-68); condylobasaf length, 29.45 (28.2-30-5), 29.34 (28.9-30.1); zygomatic breadth, 16.55 (15.8-17,4), 16.72 (16.5-16.8). Natural History-Prairie voles have been found in both dry and wet grasslands but tend to live in the drier areas when sympatric with meadow voles. Dominant plant cover consists of grasses and clover through which they have extensive runway systems. Burrows lead to nests and food chambers 6 to 18 inches below ground surface. -. Diets locally are not documented but studies at Lawrence, Kansas, showed a preference to dicotyledons, although grasses dominated the vegetation. Grasses, seeds, and some insects supplement the diet. Reproduction occurs year-round with no distinct season but reaching a height around March and a drop in winter dependant upon the percentage of adults in the population. Litter sizes tend to vary seasonally, averaging about 3.9 young. Females mature at 4 to 6 weeks. They have three or four litters per year. The gestation period is 21 days. Predators include coyotes, raccoons, owls, and hawks, but predation does not seem to affect population densities strongly. Populations fluctuate in two- to six-year cycles, dependant on available adults, due to causes wldch are unknown but which may be related to aggressive behavior, immigration, and abundance of vegetation. Selected Ref erences-doate and Williams (1978) ; Cruzan (1968) ; Fitch (1957); Jameson (1947); Martin (195610
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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
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LITERATURE CITED Allen, J. A. 1877.
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FIGURE 2. Skull and mandible of Syl
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4 MAMMALIAN SPECIES 136 1939). The
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- 1904. Mammals from Southern Mexic
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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 and 124: --39- DESERT COTTONTAIL Sylvilagus
Page 125 and 126: -- 48-- THIRTZEN-LINED GmUND SQUIRR
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: --69-- MEXICAN WOODRAT ~istribution
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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