•Beaver are inherently aquatic and this is illustrated in the webbed feet that assist with swimming, the flat, fleshy tail that acts like a rudder and the dark brown, thick, soft, waterproof fur that acts as a wetsuit in frigid water.
•They have a set of transparent eyelids that function much like goggles.
•Beavers are often 35–40 inches long, including the tail and weigh 30–60 pounds.
•Most beavers build large log dams of local woods that dam up streams and create wetlands that host their favored food, aspens and willows. If living on rivers, like here at Devils Tower, they may build bank dens instead of lodges.
•Beavers are active in the evening and morning hours.
•Beavers are among the largest of rodents here in the United States. They are herbivores and prefer to eat leaves, bark, twigs, roots, and aquatic plants. They are not commonly seen at Devils Tower due to the unavailability of deciduous trees.
•Beavers are monogamous, living with the same mate for their entire lives.
•They mate once a year during January and February birthing their 3 to 4 kits 15 weeks later in their lodges.
•The beaver is a keystone species that affects habitat structure and dynamics through the damming and diverting of streams, and the felling of trees and other woody vegetation.
Porcupine (Erethizon dorsatum)
•Porcupines are second only to beavers in size as one of the largest rodents in the United States.
•They are characterized by the long, white to black, 1 inch quills that protrude from their head, back and tails. They have a darker undercoat of regular hairs that provide warmth. They have sharp claws that assist in climbing trees.
•Porcupines are nocturnal, sleeping the day away high in the trees.
•Often the best way to see porcupines is to follow bare patches on the trees where they have eaten the inner bark of trees (the cambium) and the ends of branches.
•Their lethargic lifestyle may be in response to living upon poor food sources.
•Porcupines ferment wood fiber in their guts like cows and goats.
•Porcupines hole up in dens in rocky cavities, hollow trees and logs, and emerge for nightly foraging in rocky cliffs and coniferous trees. They also use “station trees,” the tops of tall trees.
•Breeding takes place in September, October, and November before winter starts.
•A single baby Porcupine (A porcupette) is born after a seven month gestation in April or May.
•The deer mouse is grayish to reddish brown with white underparts. The finely-haired tail is darker on top and the lighter on the bottom.
•Its head has a pointed nose with large, black, beady eyes and the ears are large and with very little fur. Its 1 to 4 inch tail has very little hair.
•The deer mouse is usually ¾ of an inch to almost an inch in length and weighs between 10 and 24 grams.
•Deer mice are nocturnal and emerge to forage for insects, spiders, nuts and seeds. They hoard food during times of plenty, for when food is scarce.
•They build nests in crevices, cracks and hollows. They do not hibernate within their nest, they stay awake all winter, foraging in areas under the snow, an area called the subnivean zone.
•The deer mouse is primarily a nocturnal species. Spending most of its time on the ground, but it is also an adept climber. Activity centers around a nest and food cache.
•Deer mice form parenting bonds for a season to raise the young. They mate from March to September, producing litters of 3 to 7 young, 23 days after mating.
•Deer mice are carriers of the Hantavirus. Please be careful handling the urine, droppings and saliva of the deer mouse.
Bushy-tailed woodrat (Neotoma cinerea)
•The bushy-tailed woodrat is also called a pack rat due to a tendency to collect and store random items from their environment.
•The woodrat looks like a small rat with a hairy tail, gray to tan fur on the back with white to buff colored underbelly, large sparsely furred ears and beady black eyes.
• They weigh from a little over half a pound to a full pound, and are 11 to 18 in (28 to 46 cm) in length, half of which is tail.
•Woodrats are nocturnal, foraging for their treasures and food, all night long.
•They are on the whole, complete herbivores, eating juicy plant matter, nuts and seeds. They sometimes do take advantage of eggs and small insects.
•One of the most characteristic aspects of woodrat behavior is midden-building. Middens are often built in caves or crevices, and consist of plant material, feces, and other materials which are solidified with crystallized urine. Within these middens they have nests for sleeping and food caches.
•Breeding chiefly occurs May through August and 1 to 5 pups are born 30 to 38 days later.
•Bushy-tailed woodrats are attracted to shiny items and often steal them from campsites or buildings.
Muskrat (Ondatra zibethicus)
•The muskrat greatly resembles its larger cousin, the beaver, in shape. The difference between them is the narrow, flat, scaly tail and the size. They have dark brown to black dense fur that insulates them from their watery habitat. They have webbed hind feet for swimming and smaller front feet for digging.
•Muskrats are 16 - 25" long (including an 8-11" tail) and weigh 2 - 5 lbs.
•Muskrats are semi-aquatic mammals that inhabit areas abundant in water like wetlands, ponds, lakes and marshes. They find shelter in bank burrows and nests. The nests of the muskrats are formed by piles of vegetation, generally in 15 to 40 inches of water.
•They are mainly herbivorous, eating aquatic plants and shoots. In the winter they will search under the ice for plants and roots. They may supplement vegetation with meat, including mussels, clams, small fish and frogs.
•They do not hibernate, but do not venture far from their home. They stay within 50 feet of their homes.
•Muskrats are crepuscular and nocturnal, feeding and nest building in the cool evening and morning hours.
•Most muskrat mating takes place between June and August. Gestation usually lasts 30 days with litters of 3 to 9 young.
Masked Shrew (Sorex cinereus)
•The distinctive feature that characterizes the masked shrew and other shrews from their fellow rodents, is the sharp pointed snout bristling with long whiskers.
•The fur on the back of the shrew is brown, and the belly fur is greyish-white. The 1.5 inch naked tail has is mostly brown with a black tip.
•Their ears are almost never seen, as their size and the length of their fur covers them.
•Shrews are around 4 inches in length and weigh 0.09 to 0.14 oz.
•Common shrews occupy a diversity of habitats, most common are forests, meadows, river banks, and willow thickets. They prefer moist environments.
•85% of shrew activity happens after dark, when they forage for food like insect larvae, ants, beetles, crickets, grasshoppers, spiders, centipedes, slugs, and snails.
•Shrews mate after the cold of the winter burns off and then on through the summer. 5 to 7 young are born after a gestation of 3 to 4 weeks in a insulated nest of grasses and fur.
Last updated: May 8, 2019
PO Box 10
Devils Tower National Monument Information Line