These squirrels are strictly nocturnal and for this reason it is difficult to tell how common they really are. Found only in the forested areas they nest in woodpecker holes or in hollows in the trees or possibly build a nest among branches or utilize old pine squirrel nests when hollows are not available.
Probably common throughout most of the forests of the park.
Frequenting the more open ground in the park they live primarily on rodents. In the winter they hunt beneath the snow. I have seen them stick their heads up through the snow, look around and quickly dive beneath again.
Seldom seen but is probably found in most of the open sections of the park as it is common on all sides.
Weasels are strictly terrestrial and are very highly carnivorous and blood thirsty. Very active and courageous attacking without hesitation animals considerably larger than themselves. They have very slender, long bodies and short legs.
Reported as common in the lower northern valleys along the Gardner, Yellowstone and Lamar Rivers and occasional in other inland valleys by Bailey in 1923.
Longtail Red Fox: Vulpes fulva macrourus. This species has a longer tail than the average red fox. In color it is a reddish yellow to golden yellow with grizzled whitish; underparts white; feet and lower part of legs black.
The red fox although not common is occasionally seen in the north and northeastern sections of the park. It was at first regarded as rare but seems to be increasing somewhat in recent years.
Mountain Bobcat: Lynx rufus uinta.
Canada Lynx: Lynx canadensis. These two animals are very similar in habits though the lynx is more a dweller in the colder forest regions while the bobcat may be found in more open areas closer to habitation. Both have tufted ears and a short tail and neither of the above species has the distinct spots that are characteristic of some of the species of bobcats. The lynx is the largest of the bobcats and is slightly larger than the mountain bobcat. The bobcat has a tail seven or eight inches long with two black bands on the upper surface in front of a black tip while the lynx has a tail only about four inches long and with black only on the tip.
These animals are rare in the park area and have only been recorded in the northern section. My only observation of one was about eight miles north of the park along the Yellowstone River.
Wolverine: Gulo luscus. Heavily built animals with short legs, short ears, a short bushy tail, and long coarse hair. Appearing much like a small, short-legged bear. Total length is from 37 to 41 inches and weight from 22 to 35 pounds. It is dark brown or blackish in color with two broad, pale, lateral bands of brownish white to yellowish white from shoulder to rump.
The wolverine is a powerful and savage fighter, strictly carnivorous and well earns its name of “glutton.” It had a bad reputation among trappers for it followed their trap lines, robbed and even broke up their traps and dug up their food caches. Wolverines are no longer common in this part of the country and while there may have been a number of them in the park area some years ago they are probably only very rare visitors now.
Brown Pocket Gopher: Thomomys talpoides fuscus. The piles of dirt which suddenly appear in the grass of lawns or meadows are made by the pocket gopher. He excavates a network of tunnels below the sod line, pushing the dirt through an opening on to the surface, then filling the opening up again. Their food consists of vegetable matter such as roots, bulbs, tubers and surface foliage and green vegetation.
The pocket gopher is rather small in size, about eight inches long, including a tail of a little over two inches, and is light brown in color. The tail is only sparsely haired and the front feet are large and built for digging. The Uinta ground squirrel or picket-pin is frequently referred to by some people as a gopher, but it should not be confused with the true gopher and is seldom seen above the ground.
Found in meadows and open areas throughout the park.
Rocky Mountain Jumping Mouse: Zapus princeps. Sometimes called Kangaroo Mouse this little animal is a medium-sized mouse with greatly elongated hind legs and a slender tail nearly six inches long. Its upperparts are yellowish brown lightly sprinkled with blackish, the underparts white.
This mouse lives on vegetation and seeds. It is found throughout the park in meadows and open country but nowhere abundantly. It hibernates during the winter.
Gale Redback Mouse: Clethrionomys gapperi galei. These mice live on green vegetation, seeds, roots and stems and probably occupy most of the forested sections of the park. They live in burrows and are not very often seen. Several have been trapped in residences in Mammoth. They are active all winter under the snow.
They are small to medium sized mice with the upperparts reddish chestnut distinctly differing from the buffy gray sides; underparts whitish to yellowish gray.
Dusky Shrew: Sorex obscurus.
Mountain Water Shrew: Sorex palustris navigator. Most species of shrews are smaller than any mice, with pointed noses, minute eyes, and small ears which are hidden in the fur. They are insect eaters and like any kind of fresh meat. They are active all winter.
The dusky shrew is a sepia brown in color and is found throughout most of the park area. Mountain water shrews make their homes in banks of icy streams and are mouse-size with upper parts slaty mixed with hoary. They have larger feet than the dusky shrew and have bristly fringes along the toes with partial webs which equip them for swimming readily.
The Rocky Mountain Shrew (Sorex vagrans monticola) has been collected once in the park and it is also probable that the Masked Shrew (Sorex cinereus) is also here as it has been found in the surrounding area.
