The Voles of the Great Salt Lake  INDEX:

The Great Salt Lake is famous for its brine shrimp and birds, but there are also many mammals that live on the shore of the lake and are an important part of the shoreline, playa ecosystem.  One of these mammals is a small rodent called voles. Voles are members of the genus Mictrotus.  There are more than one hundred species of voles, each adapted to immensely varying habitat from sea level to the timber line.  Voles are important to humans because their voracious appetites can cause agricultural damage but in the Great Salt Lake Playa Ecosystem they are of food value to numerous larger carnivores. The two voles found in the in the Great Salt Lake Ecosystem are the Meadow Vole or “Field Mouse”- Mictrotus pennsylvanicus and the Montane (or Mountain) Vole - Mictotus montanus.  

What do voles look like? 
 

  

Most voles look alike and this is true with the Meadow Vole and the Montane Vole.  Meadow voles have variable color from yellowish brown to reddish brown peppered with black to blackish brown.  They are usually grey with silver-tipped hair below and a long tail dark above and paler below.  The feet of Meadow Voles are dark.  The Meadow Vole is 140 -195 mm in length, 33-64 mm tall, and weighs between 20 -70 grams.  The Montane Vole is similar with a grizzled brown or blackish color above, often with buff tint and gray below.  Montane Voles are moderately long with a bicolored tail.  Feet of Montane Voles feet are dusky or silvery gray.  They are 140 -192 mm in length, 31 - 69 mm tall and weight between 37-85 grams. 

 

Where do voles live? 

In the World - North America 
 

In North America -  
Meadow Vole: Alaska (except for Northern sections) and Canada south and east to Northern Washington, Idaho, Utah, New Mexico,Wyoming, Northern Missouri, Northern Illinois, Kentucky, Northeast Georgia, and South Carolina. 

 

Montane Vole: South-central British Colombia, Eastern Washington, most of Oregon, Northeast California east to Souteast Montana,Eastern Wyoming, portions of Northern Utah and Western Colorado,extending south into New Mexico and extreme East Arizona. 

In the Great Salt Lake Ecosystem - Salt Grass Zone 
In general, Voles lives in runway and burrow systems under the grass cover.  
Meadow Vole: Lush grassy fields and marshes, swamps, woodland glades and mountain tops. Like Meadow voles, Montane voles construct a system of burrows 
among the grass.  Voles hide in the dense grass vegetation and retreat into their tunnel system to seek refuge from predators. 

 

What part do voles play in the Great Salt 
Lake Food Web? 

What do voles eat? 

Voles eat a wide variety of foods including, almost any grasses, or herbaceous plants as well as seeds.  However studies have shown that the Meadow and Montane voles that inhabit the Salt Grass Zone rely virtually entirely on salt grass (Distichlis stricta) for food resource throughout the year.  Voles create their distinctive grass cuttings by reaching up and cutting of the stalk then pulling it down and cutting again until the seeds are reached.  All of the grass with the exception of the tough outer stalk is eaten by the Vole.  Their voracious appetite results in voles eating almost its own weight in food daily. Since many types of insects find refuge in the tunnel systems of voles, they also could provide an important source of protein during certain times of the year.  

Who eats voles? 

Many carnivorous inhabitants of the Great Salt Lake depend of voles for food resources.  Predators of voles include carnivorous mammals such as badgers and coyotes, snakes, and predatory birds such as the marsh hawks and owls.  Because voles are relatively defenseless and so widespread they constitute the mainstay in the diet of many carnivores. 

How do voles reproduce? 

Voles put a large portion of its energy into high, rapid, and early 
reproduction rather than growth and longevity.  The gestation period is 21 days and litters range in size from 1-11 offspring are produced from spring through fall. Up to thirteen litters have been produced in a single season.  A study by Negus et al. (1985) has shown that vole reproduction may be initiated by a chemical factor, 6-methoxybenzoxazolinone (6-MBOA).  (6-MBOA) occurs in sprouted wheat.  The study showed that young sprouts of salt grass in late February are high in (6-MBOA), late June samples are lower and there is no detectable (6-MBOA) in salt grass samples from August.  The seasonal onset of breeding coincides with the appearance of (6-MBOA) in the newly sprouted salt grass and supplemental (6-MBOA) also can initiate breeding in a non-breeding winter population.  

If a vole population grows too large they can be serious pests in agricultural areas such as orchards where they remove the bark of the tree in a circle at the base, “girdling trees” and killing them.  

Are there any other small mammals in the Great Salt Lake ecosystem?  

There are also many other small mammals that live on the shore of the lake or on the dry desert uplands adjacent to the saline playas. and are an important part of the ecosystem.  
These small mammals include: 
· the least chipmunk - Eutamias minimus pictus 
· little pocket mouse - Pergnathus longimembris gulosus 
· kangaroo mouse - Microdipodops megacephalus leucotis 
· ord kangaroo rat - Dipodmys ordii pallidus 
· chisel toothed kangaroo rat - Dipodmys microps bonnevillei 
· deer mouse - Peromyscus maniculatus sonoriensis 
· harvest mouse - Reithrodomys megalotis megalotis 
· grasshopper mouse - Ocychomys leucogaster utahensis 
· antelope ground squirrel - Citellus leucurus leucurus 

What do these mammals look like? 

These small mammals are all rodents and may look alike.  Characteristics of each mammals are as follows: 
· The least chipmunk is a small chipmunk with varying sizes. In dry regions  a muted yellowish gray above with tan dark stripes. In moister areas, brownish gray with black side stipes.  All least chipmunks have pale white stripes of equal width, 2 white areas on flanks continue to base of tail, sides are orange brown and belly grayish white.  The tail is long and brown above grayish yellow below, with hairs black tipped. 
· The little pocket mouse is a soft furred grayish yellow or buff above with interspersed black hairs that vary with color of soil.  Under parts are buff, brownish, or white.  The tail of the little pocket mouse is uniformly pale brownish and there are two white patches at the base of the ears.  They are 110 -151 mm long, 53-86 mm tall and from 7-9 grams in weight. 
· The kangaroo mouse is blackish or dark grayish above, with gray hairs at the base and white below.  The tail of the kangaroo mouse is thickest in the middle, tapered at both ends, black tip, and no tuft.  The hind foot has hair on the soil.  Kangaroo mice are 148 -177 mm long, 68 -103 mm tall and from 10 -17 grams in weight. 
· The ord kangaroo rat is buffy reddish, or blackish above and white below.  The tail is crested but not white tipped and relatively shorter than other kangaroo mouse.  There is a dark tail stripe below extending to the tip.  There may be conspicuous white spots at the base of the ears and above the eyes.  The hind foot has 5 toes.  The ord kangaroo mouse is 208 -282 mm long 100-163 mm tall and from 50-96 grams in weight.  
 · The chisel-toothed kangaroo mouse is also buff to dusky above and whitish below.  It has a long tail with white side stripes narrower than dark upper and lower stripes.  The hind foot has 5 toes. The chisel-toothed kangaroo mouse is 244-297 mm in length, 134 -175 mm tall and from 55 -75 grams in weight. 
· The color of the deer mouse varies with geographic area, it is often grayish to reddish above and white below.  The tail is distinctly bicolored and short-haired.  The deer mouse ranges from 119-222 mm in length, 46-123 mm in height and 10-33 grams in weight.  
· The harvest mouse is brownish above, buff along the sides, and white below.  There is an indistinct broad strip down the spine.  Tail length is less than that of head and body.  They are 114-170 mm long, 50-96 mm tall and from 9-21.9 grams in weight. 
· The grasshopper mouse is a heavy bodied mouse with 2 main colors phases above; grayish and cinnamon-buff and white below.  The tail is short, thick and bicolored with a white tip. It is usually less than one third total length.  The grasshopper mouse is from 130 -190 mm long 29-62 mm tall and weights 27-52 grams. 
· The antelope ground squirrel has buff upper parts in summer gray in winter.  There is one narrow stripe on each side and its underparts are white with black-tipped hairs forming narrow borders.  The upperside of the tail has one black band and ears are small.  Length is from 194-239 mm, 54-87 mm tall and 85-156 grams in weight. 

Where do they live in the Great Salt Lake? 

Great Salt Lake Ecosystem - 
Pickleweed Zone - deer mouse and ord Kangaroo rat  
Vegetated-Dune Zone - chisel-toothed kangaroo rat (dominant), antelope ground squirrel, least chipmunk, kangaroo mice, pocket mice, harvest mice, deer mice, and grasshopper mice. 
Shadscale Gray molly Zone - deer mice (sparse) 
Shadscale Gray molly-Greasewood Zone - antelope ground squirrel, least chipmunk (abundant), chisel-toothed kangaroo rat, deer mice (abundant) 
Greasewood Zone - antelope ground squirrel, least chipmunk, deer mice as well as others in sparse numbers. 
Shadscale-Budsage Zone - chisel-tooth kangaroo rat (dominant), deer mouse (sparse), antelope ground squirrel (sparse). 
Juniper-Brush Zone - ord kangaroo rat (dominant), antelope ground squirrel, deer mouse. 
Mixed-Brush Zone - chisel toothed kangaroo rat (dominant), deer mouse, antelope ground squirrel, ord kangaroo rat (sparse), little pocket mice, grasshopper mouse. 

What do they eat?  

ord kangaroo rat - Mostly succulent terminal leaf buds and leaves.  Also greasewood, tumbleweed and grasses. 
chisel-toothed kangaroo rat - Mostly shadscale. Also four-winged saltbush and greasewood. 
little pocket mouse - Rice grass, alkali sacaton, pepper grass and tumbleweed.  
antelope ground squirrel - Alkali sacaton shoots, rice grass, cheat grass, galleta grass, seeds, as well as carnivorous habits 

Who eats them? 

These small mammals are prey for the larger carnivores of the Great Salt Lake.  These include badgers, kit foxes, coyotes, and carnivorous birds.  

References 

Burt, William H., Grossenheider, Richard P. A Field Guide to the Mammals. New York, Houghton Mifflin, 1980. 

Cahalane, Victor A. Mammals of North America. New York, MacMillian Company,1947  

Fautin, Reed W. Biotic Communities of the Northern Desert Shrub Biome in Western Utah. University of Illinois, 1946 

Hall, E. Raymond Ph.D. The Mammals of North America. Second Ed. John Willey and Sons, New York, 1981.  

Whitaker, John O. National Audubon Society Field Guide to North American Mammals. Chanticleer Press, New York, 1996. 

Vest, Dean E. The Plant Communities and Associated Fauna of Dugway Valley in Western Utah.  University of Utah, 1962 

Zeveloff, Samuel I. Mammals of the Intermountain West. University of Utah Press. 1988 

University of California. (1997) UC Pest Management Guidelines <URL-http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7439.html> (1999, Oct.). 

URL-http://www.umm.edu/~classx/mammal/vole.html