Part 6

At one time the marten was thought to depend on the red squirrel for his daily fare, but recent studies indicate that ordinarily relatively few red squirrels are eaten. A food-habits study made at Castle Rocks near the northwest corner of the park showed that the martens there were living primarily on meadow voles and the red-backed mouse. Blueberries were eaten in winter as well as in summer. In Wyoming, I have found martens feeding extensively on blueberry, rhamnus, haw, and mountain ashberries by choice at a time when voles and other foods were plentiful. Like the fox and coyote, they have a strong predilection for berries. In slide rock, they manage to capture an occasional pika.

The marten breeds in July and August, but the young are not born until 9 months later. The long gestation period for such a small animal is due to the delayed attachment of the fertilized egg to the uterus. Except for the period when the female is followed by young, and during the breeding period, martens travel alone.

In Grand Teton Park, Wyoming, where I had much opportunity to observe martens, I found that, although they seldom captured a red squirrel, in their vagabond life over their home area, they did use red squirrel homes for sleeping. The marten might spend a few days resting in a squirrel’s spare nest, then move on to another squirrel domicile for a few days. The squirrels suffered only the inconvenience of an unwanted guest, and perhaps the temporary loss of a favorite bed.

Mink Mustela vison ingens

The mink is the amphibious member of the weasel family. He lives along rivers and lakes and probably forages more in the water than on land. Fish, frogs, insects, snails, crayfish, rabbits, muskrats, and mice all appear on his bill of fare. In the country between the mouth of the Yukon and the Kuskokwim River, the mink is said to subsist largely on Alaska blackfish (Dallia pectoralis). So abundant were the mink in the area that the Eskimo were called “mink people.” The muddy waters in this watery region apparently supported enough blackfish for both the mink and the natives. This fish is said to have been the chief food of the natives. It is very tenacious of life. Kegs of live fish, packed densely, were kept for food in the dwellings. A steady slow rotary movement of the mass of fish brought each fish to the surface at intervals for a gulp of air. When a frozen blackfish is thawed, it is said to become as lively as ever.

Mink tracks have been noted along the Nenana River, but over most of the eastern half of the park the mink is rare.

River Otter Lutra canadensis yukonensis

The otter is rare in the park. It was reported present in Wonder Lake some years ago and tracks in the snow were reported at Savage River. It probably occurs in the Nenana River, along the eastern park boundary.

The otter, a member of the weasel family, has become adapted to life in the water. His body is about 3 feet long, and his long muscular tail is over a foot long. His cousin, the sea otter, plentiful in the Aleutian Islands, is much larger and more specialized for an aquatic life.

I have watched a family of otters in Grand Teton Park fishing for an hour or longer. They kept diving steadily, and occasionally one would come up with a small fish which he would proceed to eat, beginning at the head. Larger fish are taken ashore. Trout, chubs, and suckers were available but numerous droppings showed that the otter were feeding chiefly on the chubs and suckers. The fish taken were no doubt those most easily captured. A few crayfish were also eaten. This particular family was living in a large beaver house also occupied by beavers. They entered their chamber by land and apparently lived upstairs above the beaver’s part of the house with its underwater entrance.

In winter the otter frequently travels over the snow from one piece of water to another. In these travels he slides on his belly down all slopes and sometimes even on the level. In play, a family may repeatedly climb a mudbank or a snowbank to course down a slide leading into water.

Short-Tailed Weasel Mustela erminea arctica

Two species of weasel occur in the park. The larger one with a black-tipped tail is called the short-tailed weasel, and the smaller one with an extremely short and all-white tail is the least weasel.

Both weasels are brown in summer and white in winter, a protective coloration no doubt useful in escaping detection. In some southern parts of their ranges these weasels remain brown all year, and in intermediate areas part of the population turns white in winter and part of it remains brown. It is apparent that climate has an effect on coat color, the specific factor being the presence or absence of snow on the ground.

It has been pointed out that the short-tailed weasel is much larger in the north than in the southern part of the range. In Wyoming and Colorado, where the tiny least weasel is absent, the short-tailed weasel approaches the least weasel in size and probably fills that weasel’s niche in the environment.

The food of the short-tailed weasel probably consists chiefly of various species of meadow mice and lemmings. Observations indicate that ground squirrels and rabbits may occasionally be captured. Shrews no doubt are also on the menu.

In winter, weasel tracks form an odd pattern. Their jumps are alternately long and short, and often they make an erratic trail. Frequently the tracks show that the weasel disappears and travels beneath the surface for a stretch before reappearing.

Even though weasels are not very palatable because of their well-developed musk glands, they nevertheless are often preyed upon. It is a case of coyote or fox capturing any small animal that moves and examining the victim afterwards. Weasels are often left uneaten.

Least Weasel Mustela rixosa eskimo

The range of the least weasel is circumpolar. In North America it is found over most of Alaska and Canada, and southward to Montana, Kansas, North Carolina. It is widely dispersed but apparently nowhere abundant. This tiny weasel is only 6 to 6½ inches long with a maximum tail length of 1½ inches. It is the smallest living member of the carnivores and weighs no more than a meadow mouse. The tail is pure white, lacking the black tip present in other weasels.

I have a record of four specimens from the park. One captured in a mousetrap was 5½ inches long, the tail measuring less than 1 inch. I found a dead one at an eagle perch on a ridge top, and remains of two others on gravel bars, apparently discarded after being captured.

A sourdough on the Koyokuk River with whom my brother and I stayed one night, had a least weasel spending the winter with him. It had the run of the cabin and was very tame.

Apparently the chief food of the least weasel is mice, some of them about as large as himself.

Snowshoe Rabbit Lepus americanus macfarlani

Like the ptarmigan and the northern weasel, the snowshoe rabbit, or varying hare, each autumn changes from a dominantly brown summer coat to a white winter ensemble. (In Washington where snow is scarce in its habitat, the snowshoe rabbit remains brown the year round.) His coat color blends at all seasons with his background, so all he need do to be fairly sure of escaping visual detection is to have confidence in his camouflage and sit motionless. The fur is so long, thick, and warm that he can sit all day in fifty below zero weather without freezing. His large hind legs are equipped with snowshoe feet, an obvious advantage in snow country.

The most favorable rabbit habitat is the brushy country along the east and north boundaries. Here a few may always be found. Out in the park they are quite scarce except in those years when the population is at or near a peak.

In winter, the rabbits feed on bark gnawed from various shrubs and saplings. Willow, dwarf birch and alder, because of their high palatability and abundance, are especially important winter foods. In years of rabbit abundance, I have seen patches of willow and dwarf birch trimmed to the snow line. At such times large willow brush may show a white band 2 feet wide where the rabbits have gnawed the bark within reach of the snow line. As the snow deepens, some foods are buried but the change of level brings new food supplies within reach. A variety of other shrubs are also eaten at this season. Spruce bark is relished. Porcupines, and also red squirrels, feeding in a spruce tree inadvertently add to the rabbit menu many dropped spruce twigs. In summer, the rabbits turn to a variety of fresh green foods.

The young of the snowshoe rabbit are furred and active when born and apparently there is no real nest provided. (In the cottontail branch of the family the young are born hairless, helpless and in a warm nest.) The litters may vary from one to six. The gestation period is about 36 days. The young are weaned (in captivity) when about 4 weeks old. The females breed again soon after a litter is born. It seems likely that a female may have as many as three or four litters during a summer. A male is apparently with a female for only a short time.