Fauna Series No. 3

Fauna of the National Parks — No. 3 Birds and Mammals of Mount McKinley National Park

Mammals

DESCRIPTIONS OF MAMMAL SPECIES

YUKON LEMMING
Lemmus yukonensis [MERRIAM]

GENERAL APPEARANCE.—Lemmings resemble wooly, short-tailed meadow mice, but the soles of their feet are hairy, lacking the bare tubercles found on the feet of meadow mice. The long pelage of the lemming is of a rusty color and is soft in texture. The ears are short, almost covered by the long hair of the head and neck. The tail is very short, being often less than the length of the hind foot. Length, 5 inches; tail, 0.7 inch; hind foot, 0.8 inch.

IDENTIFICATION.—The exceedingly short tail and, dorsally, the long, loose, reddish pelage distinguish the lemmings from all other mice found in the McKinley region.

DISTRIBUTION.—The lemmings are characteristic rodents of the treeless Arctic prairies over much of northern Alaska. They are abundant at times above timber line in Mount McKinley National Park, but they are almost, or entirely, absent during many seasons. Near Wonder Lake, in 1932, I obtained a single dried-up specimen.

HABITS.—In 1906, Charles Sheldon found lemmings and other mice to be rare in the Toklat region, but they were abundant there the following year. He states (1930, p. 121) that in 1907, "the lemmings bred in colonies of 5 to 12 holes close together, connected underground . . . At least two litters of young had been reared, and by the middle of August the females . . . contained from five to seven embryos each." The lemmings were active all day and were very tame, but whenever an Alaska jay flew near them all the mice suddenly rushed into their holes. Both jays and short-billed gulls were seen to dart down, pick up, and to devour young mice.

When the lemming population increases so that their food supply is exhausted swarms of these rodents leave for new pastures. Hawks, owls, foxes, ravens, gulls, jaegers, and other natural enemies of mice follow these fleeing hordes and prey upon them. At such times also disease often breaks out in the mice and reduces their numbers to a mere handful. Then the lemmings begin to breed up again and the whole cycle is repeated.

DAWSON RED-BACKED MOUSE
Evotomys dawsoni dawsoni [MERRIAM]

GENERAL APPEARANCE.—A small mouse with a broad rusty red back. The ears are short and but slightly longer than the fur. The eyes are small and the tail is fairly short, being less than twice as long as the hind foot. Length, 5.8 inches; tail, 1.3 inches; hind foot, 0.8 inch.

IDENTIFICATION.—The tail which is decidedly longer than the tail of the Yukon lemming and the bright red back and small size of this mouse distinguish it at once from the lemming which is the only other mammal in the park with which it is likely to be confused.

DISTRIBUTION.—Red-backed mice are found in the wooded territory over northern North America. In Mount McKinley National Park we found the Dawson red-backed mouse to be most abundant in the black spruce forests near timber line. This inhabitant of the woods was found to be the mouse which most frequently invaded and became resident in human habitations.

The population of red-backed mice, unlike that of the shrews, lemmings, and meadow mice, appears to be fairly constant and lacks any great cyclic fluctuations.

HABITS.—On May 21, 1926, in an old tent that had been used as a stable at Savage River, mouse traps were set. Three adults, and one immature mouse about two-thirds grown were caught. From this and other data it would appear that the red-backed mice are about the first mice to breed in the spring. Early on the morning of May 30, 1926, a mother red-backed mouse was seen to run across our cabin floor carrying one of her offspring in her mouth. The young mouse was grasped by the skin of its abdomen. While carried by its mother it curled up around her face. Its hind feet, tail, and nose were firmly pressed against the side of the parent's head. In the mother's haste to escape she dropped the young mouse. Upon examination it was found to be 2-1/2 inches long and to weigh 12 grams. This little mouse had no sign of tooth marks where its mother had grasped it. The eyes had not yet opened although the little animal was well furred. Tests proved that its sense of smell was very keen and was used in place of sight in locating its parent.

Red-backed mice were also found at Headquarters, Igloo Creek, and at Copper Mountain well above timber line.

An adult female red-backed mouse with mamriae which showed plainly that she was still nursing her first litter of young was trapped on June 1, 1926, on Savage River at 2,800 feet altitude. Further examination of this nursing female showed that she contained eight small embryos. This circumstance leads us to conclude that at least two, and perhaps—as Charles Sheldon has suggested—even three litters of young may be raised in a single short summer season.

DRUMMOND MEADOW MOUSE
Microtus drummondi [AUDUBON and BACHMAN]

GENERAL APPEARANCE.—A short chunky mouse of medium size. The length of the tail is about one and one-half times the length of the hind foot. The ears are short and well concealed in the fur of the head and neck. The fur is fine and soft in texture and is brownish in color. Drummond voles are active during the day as well as at night. These mice make well-worn narrow trails through the grass and green vegetation. Length, 5.4 inches; tail, 1.5 inches; hind foot, 0.7 inch.

IDENTIFICATION.—The Drummond meadow mouse is larger and browner than the Toklat meadow mouse, and it is smaller than the large and grayer interior meadow mouse. It is about the same size as the Yukon lemming, but it lacks the rusty red of the lemming and its tail is longer than its hind feet.

DISTRIBUTION.—Drummond voles are found from the southern boundary of Canada north almost to the Arctic Ocean and from Hudson Bay to central Alaska. In the McKinley region drummondi has been found on the Toklat and Savage Rivers at or near timber line. It is most numerous along the margins of willow thickets.

HABITS.—In 1906, Charles Sheldon found this species of mouse to be rare in the Toklat region, but in the fall of 1907 he found this and other species of mice to be abundant near his winter cabin. This coincides with my own experience in the same region, for in 1926, I found meadow mice of this and other species to be numerous, whereas in 1932, they were extremely rare or absent in the same areas. Therefore one visitor to Mount McKinley Park might find Drummond meadow mice to be exceedingly numerous while another later visitor might not be able to find them present at all.

INTERIOR MEADOW MOUSE
Microtus operarius endoecus [OSGOOD]

GENERAL APPEARANCE —A fairly large meadow mouse with a tail nearly twice the length of its hind foot. The summer pelage is rough, short, and grayish in color. The ears are fairly large. Length, 7 inches; tail, 1.6 inches; hind foot, 0.8 inch.

IDENTIFICATION.—The interior vole or meadow mouse is almost as large as the yellow-cheeked meadow mouse but it lacks the yellow patches on the cheeks and at the base of the ears which are characteristic of the latter species. The interior meadow mouse is larger and yellower than the Drummond meadow mouse and is much larger than the Toklat River vole.

DISTRIBUTION.—The habitat of this species is central Alaska. In the McKinley region we found the interior meadow mouse only in wet meadows in the timbered or wooded areas along the Savage, Toklat, and McKinley Rivers.

HABITS.—On June 20, 1926, along the upper Savage River I trapped two adult females each of which contained six well developed young that would heave been born in a few days. Two young of previous litters, though born earlier that same season, were also trapped in the same runways in which the adult females had been taken. These young mice were 3-1/2 inches in length and were nearly half-grown. Their coats were shorter and browner than the coats of their parents.

In our experience we have found the interior meadow mouse to have a very restricted local habitat and although it is widely distributed it is never found in large numbers. Too, they do not seem to fluctuate in numbers from season to season to the same extent as do some of the other mice.

TOKLAT RIVER VOLE
Microtus miurus oreas [OSGOOD]

GENERAL APPEARANCE.—A small yellowish meadow mouse with a very short tail which is only slightly longer than the animal's hind foot. The ears are short and nearly hidden in the dense fur. This vole inhabits the dry open tundra. Length, 6 inches; tail, 1 inch; hind foot, 0.8 inch.

IDENTIFICATION.—The small size, short tail and yellowish or ocherous color of this vole serve to distinguish it at once from the other meadow mice of the region.

DISTRIBUTION.—The main Alaska Range of south central Alaska is the home of the Toklat River vole. In Mount McKinley National Park it has been found along the bare ridges of the main range as high as 4,600 feet and along the Toklat and Savage Rivers' rocky gravel bars as low as 2,800 feet.

HABITS.—Early in June 1926, we found these mice, as has been stated, to be abundant on the open gravel bars along the Savage River. There were no regular Microtus runways, only small clean-cut burrows about an inch its diameter which ran 2 or 3 inches under the moss and which led underground to their nests made of dry grass.

During the first half of June these mice were mating. They were exceedingly active during the entire 24 hours of each day. On June 12, 1926, an adult female was found to contain eight foeti, each three-fourths of an inch in length and nearly ready to be born. Another female was found to contain seven embryos on June 29; and four other females trapped between June 14 and June 26 contained six embryos each. Sheldon found that as many as three litters of young were raised in a single season. Our own studies corroborate Sheldon's findings. Thus, this species has a relatively high rate of reproduction.

Sheldon reports (1930, p. 121) "Twice I saw a jay dart quickly down, pick up a young meadow mouse and fly to a tree and eat it."

On June 11, 1926, we found numbers of short-billed and herring gulls sitting about a meadow inhabited by many Toklat River voles. The gulls were quietly waiting, either singly or in small groups of three or four, watching for the meadow mice. The young voles are not suspicious and they run about freely in the daytime. As I have said before, it is truly a wonderful sight to see a whole dark green field dotted with white-breasted gray-backed gulls motionless as statues. It is interesting to note that on June 2, 1932, this same area was still covered with 6 feet of snow.

In the fall of 1907, Sheldon found these and other mice to be "incredibly abundant" in the Toklat region where they had been relatively scarce the previous season. In 1932, I was unable to find or to catch a single vole of this species in the identical areas where I had found them so abundant in 1926.

YELLOW-CHEEKED MEADOW MOUSE
Microtus xanthognathus [LEACH]

GENERAL APPEARANCE.—A very large meadow mouse with bright rusty yellowish patches on the side of the nose and at the base of the ear. The general color of this mouse is dark sepia on the dorsal surface and dusky gray on the belly. The tail is faintly bicolored and about twice the length of the hind foot. Length, 8.5 inches; tail, 2 inches; hind foot, 1 inch.

IDENTIFICATION.—The large size and the distinct yellow patches on the cheeks and at the base of the ears are the best field characters for this species.

DISTRIBUTION.—This meadow mouse is found from central Alberta north to the Arctic coast and west to central Alaska. In 1907, Charles Sheldon found this species to be numerous on the Toklat River where he collected some specimens.

HABITS.—Very little is known regarding the habits of the yellow-cheeked meadow mouse in Mount McKinley National Park beyond the few specimens which Sheldon collected on the Toklat River. In our experience it is the rarest species of meadow mouse thus far found in the park.

NORTHWESTERN MUSKRAT
Ondatra zibethica spatulata [OSGOOD]

GENERAL APPEARANCE.—A large robust water meadow mouse. It has broad hind feet which are partly webbed between the toes. The scaly tail, which is about as long as the body, is compressed so that its vertical measurement is much greater than its width across. The muskrat's coat consists of long polished guard hairs and an rudder coat of soft dense fur which keeps out both the cold and water. The ears are short and well-concealed in the dense fur. Length, 21 inches; tail, 10 inches; hind foot, 3 inches.

IDENTIFICATION.—The aquatic habits and the webbed hind feet of this animal distinguish the muskrat from all other rodents in the McKinley region except the beaver which is a much larger animal with a broad tail. The beaver's tail is not compressed as is the Northwestern muskrat's tail; it is flattened.

DISTRIBUTION.—Muskrats always live in or near water. They occur over most of North America and are found from the Atlantic to the Pacific and from the Gulf of Mexico to the mouth of the Mackenzie River. In the McKinley region they have been found at Wonder Lake and at several of the other smaller lakes along the north boundary of the park, usually below 2,000 feet.

HABITS.—From time to time muskrats are captured by hawks, owls, and eagles. In some instances these birds have been known to carry their victims several miles before eating them. At the base of a rocky pinnacle on Savage River the remains, including the distinctive scaly tail, of a muskrat, were found on May 23, 1926. The skin had been dropped by some large bird of prey after it had eaten the meat. This muskrat must have been carried in from a distance of several miles for there were no ponds or lakes within 3 or 4 miles of the place where the carcass was found.

The muskrat is rather rare in the park. It has never been found in numbers there.

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Last Modified: Thurs, Oct 4 2001 10:00:00 pm PDT
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