Part 10

This little animal is very prolific and usually has several litters each year, with each litter consisting of from four to eight young. Were it not for their many enemies they would soon overrun the grass lands and do untold damage. As it is, their enemies, which are practically every predatory animal and bird, can barely keep them in check. Meadow mice serve as a valuable source of food for the smaller predatory animals such as coyotes, foxes and for the various hawks and owls.

There are four species of these mice that have been found in Yellowstone Park:

Sawatch Meadow Mouse: Microtus pennsylvanicus modestus. A medium-sized mouse with upperparts dull ochraceous, sprinkled with black. Underparts soiled whitish to ashy or cinnamon. In winter many black hairs along upperparts and underparts with wash of creamy white. Total length 7 inches, tail 1.8 inches. Has been found at Mammoth Hot Springs, Upper and Lower Geyser Basins and Shoshone Lake.

Dwarf Meadow Mouse: Microtus montanus nanus. A small-sized, rather short-tailed mouse with upperparts everywhere mixed gray, sepia and blackish, feet grayish; tail bicolor, dusky gray and whitish; underparts whitish. Total length 6 inches; tail 1.6 inches. Found in the grass of meadows and upland slopes over most of the park and appear to be the most abundant and generally distributed of the meadow mice in the park.

Cantankerous Meadow Mouse: Microtus longicaudus mordax. Resembles Sawatch meadow mouse in size but the tail is longer, ears larger, and color grayer. Upperparts grayish bister; sides grayer, underparts whitish. Lighter colored in the winter. Total length 7.4 inches; tail 2.8 inches. These mice have been found at Mammoth and Tower Fall and are probably common in most of the meadows of the park, equally at home on dry ground or in mountain streams.

Big-footed Meadow Mouse: Microtus richardsoni macropus. Largest of the meadow mice. Total length 8.8 inches; tail 2.8 inches. Upperparts dark sepia mixed with black, sides paler, feet gray; tail bicolor sooty whitish; underparts washed with silvery-white. In winter grayer above, more white below. Usually found close to water where they swim much in the manner of muskrats. This mouse had been taken at Heart Lake and its runways seen in marshy meadows of most of the western part of the park.

WOOD RAT Gray Bushytail Wood Rat—Neotoma cinerea Colorado Bushytail Wood Rat—Neotoma cinerea orolestes

Pack Rat or Trade Rat is the name commonly applied to this individual, represented in the park by both of the above forms. Pest of the stations and patrol cabins because of his fondness of getting into buildings and collecting items of every description, especially those of shiny appearance. These are packed to his nest, which is located either in rock piles, cliffs or whenever possible in or around buildings. He cuts open food containers, bedding and other contents and makes a general mess.

He frequently leaves some object in place of the stolen article, hence the name trade rat. However, this trade is probably due to his dropping something that he was already carrying, when he spied the new object that was more attractive, rather than any desire to make a fair trade. They gather anything that is of a convenient size to carry.

The wood rat is a very clean animal, of no relation to the common barn rat except in superficial resemblance. A vegetarian in diet he lives on green vegetation such as grass and foliage, fruit, bark, roots, fungi, seeds and nuts. He is active all year but seldom accumulates much of a store of winter food.

Mainly nocturnal in habit, they are, however, occasionally seen in the daytime. Their principal enemies here are hawks, owls, weasels, coyotes and martens.

The young, from three to six in a litter, are born in June or July and are duller in color than the parents.

General description: Large in size, mouse-like in appearance. The fur is fairly long, soft and grayish buff in color, darker in the Colorado form, on the upperparts, white underparts and feet, and a large, bushy, flattened almost squirrel-like tail. Total length 15 to 16 inches. Sexes equal in size.

Where found: Throughout the park. The gray wood rat mainly in the transition zone in open country along the Yellowstone, Lamar and Gardner Rivers and around Mammoth. Colorado wood rat in higher portions of the park.

ROCKY MOUNTAIN MUSKRAT Ondatra zibethica osoyoosensis

Quiet streams or the shallow grassy margins of ponds and lakes are the home of this valuable little fur-bearing animal. More valuable than many people realize since few know that he is the Hudson Seal and other trade names of our popular fur coats. Ironically, muskrat fur is used as an excellent imitation of his greatest enemy, the mink, in the mink-dyed muskrat coats.

A hardy little animal that lives much like the beaver, in bank dens with underwater entrances or in dome-shaped houses made of rushes, grass, turf and mud instead of the coarser sticks and branches used by the beaver. In these houses or bank dens they spend the winter in comfort. Remaining active all of the year and seldom storing any food, muskrats are out in the coldest weather.

Their food consists of bulbs and tubers, roots, tender portions of numerous marsh and water plants, sedges, grass and clover, and possibly some small aquatic animal life, salamanders, etc. In the winter it is sometimes necessary to make extensive excursions under the ice in search of food.

The young are born in the house or bank nests in May or June, usually six or eight in a litter. In lower, milder sections more than one litter is raised during the year. Fortunately muskrats are prolific breeders.

The name muskrat originated from the fact that there are two glands near the base of the tail that contain the strong though not unpleasant musk, which may be left at intervals about his haunts possibly as signs or marks of possession. While several may use the winter house the muskrat is ordinarily rather fussy and gets into frequent fights over territorial rights.

General description: A rather large, robust, somewhat rat-like appearing animal, with short legs and broad feet, the hind ones partially webbed; tail long, scaly and sparsely haired, flattened laterally. Ears scarcely showing above fur which is dense with longer guard hairs. Upperparts are dark brown, underparts lighter in appearance. Total length 23½ inches, tail 10 inches; weight about two pounds.

Where found: Throughout the park along moving streams, like the Yellowstone River between Lake and Canyon, and most of the ponds and lakes. Frequently working in the morning and latter part of the afternoon as well as at night.

PIKA Ochotona princeps ventorum

This little Pika, Cony or Rock Rabbit of Yellowstone is in reality a diminutive, tailless rabbit. Common in the higher elevations wherever loose rock piles and slides offer suitable locations for his home.

Timid and secretive in nature and possessing a protective coloration that makes them hard to locate in their rocky homes, the pikas are not often noticed by the majority of park visitors. The call of a pika, a squeaky bleat, has an elusive quality that confuses the hearer as to the direction in which it originated.

The best indications of the habitation of the pika are the small stacks of hay among the rocks. He is an industrious little farmer and is usually busy during the summer cutting and curing grass and plant foliage for winter use. This material is first put in the sun to cure, then piled in sheltered places among the rocks where it will be accessible during the winter when the snow has made a protective blanket over the landscape. In protected cavities and runways beneath the rocks, with an ample supply of hay, the pika has nothing to worry about during the winter months and find no need to hibernate. Just what family activities they have during this period is not known.

If an observer remains quiet near their rocky homes he may soon be rewarded by a sight of them running silently about over the rocks, and it may occasionally be possible to approach close enough for a picture.

The young, from three to five in number, are born from late May or early June to early September. Due to their secretive nature and the location of their homes not a great deal is known yet about the home life of the pika.