This animal has a voracious appetite. Said to eat several times its weight every day, the short-tailed shrew is aided in subduing its prey by a poison found in its saliva.
Smoky Shrew (Sorex fumeus)
The smoky shrew nests under rotting logs, in rocky crevices, stone piles, and under discarded lumber.
Pygmy Shrew (Sorex hoyi)
The smallest mammal in Pennsylvania and throughout the United States. There are fewer than two dozen pygmy shrew specimens from Pennsylvania in museum collections and all of these have been collected in the last 15 years.
Silver-haired Bat (Lasionycteris noctivagans)
This species migrates south of Pennsylvania for the winter.
Red Bat (Lasiurus borealis)
One to four young are born in June and cling to the mother in flight until they are too large for her to manage.
Hoary Bat (Aeorestes cinereus)
This, the largest and most strikingly colored bat in Pennsylvania, migrates when the weather becomes too cold to forage on insects. It is believed that its migration pattern follows that of insectivorous birds. With its 15-inch wingspan, its flight has been described as erratic and clumsy. However, most sources say that it is rarely observed because of its habit of emerging well after dark.
Snowshoe Hare (Lepus americanus)
The snowshoe hare is also called the varying hare. This animal is rusty brown in summer but in the autumn, its guard hairs are replaced by new white hairs which give the mammal an overall white appearance. In addition to allowing this mammal to blend into a snowy landscape, the structure of the white hair includes more air which provides for greater insulation during the colder months. In early spring, the hare goes through another molt which returns it to a summer coat. During the fall molt, the fur on its feet becomes much thicker, aiding in insulation. The extra fur also allows the snowshoe hare to move easily on top of deep snow.
Appalachian Cottontail (Sylvilagus obscurus)
This species was recently recognized as separate from the New England cottontail.
Gray Squirrel (Sciurus carolinensis)
The gray squirrel easily tolerates life around humans in parks and other small stands of trees where it may build huge leaf nests as well as denning in hollow trees.
Fox Squirrel (Sciurus niger)
One squirrel may bury hundreds or even thousands of nuts. Although many are found again, squirrels contribute heavily to the planting of new trees when unfound food caches sprout and grow.
Eastern Chipmunk (Tamias striatus)
This small ground squirrel builds an extensive burrow system, with multiple entrances, where large caches of food are sometimes stored. Food may also be stored in a small hole which the chipmunk excavates and then covers. Unlike the gray squirrel that hides a single acorn in each hole, large stores may be transported in the cheeks of a chipmunk for storage at a single site. Trees are sometimes climbed in search of food.
Red Squirrel (Tamiasciurus hudsonicus)
Although they are tree squirrels, these animals also burrow and may store food underground.
Northern Flying Squirrel (Glaucomys sabrinus)
Not frequently seen by people, the northern and southern flying squirrels are not easily distinguished from each other at a distance. Young flying squirrels are sometimes found on the ground, in a disoriented state, after a heavy storm.
Southern Flying Squirrel (Glaucomys volans)
This species is common in the woodlands of southwestern Pennsylvania but it is not frequently seen because it is active at night. The animal “flies” by spreading its limbs out to the sides and flattening the furry membranes into a sail that allows it to glide down and forward for distances of up to 40 feet.
White-footed Mouse (Peromyscus leucopus)
Found throughout the Commonwealth, this is one of the most common mammals in Pennsylvania.
Red-backed Vole (Clethrionomys gapperi)
Like many herbivores, this mouse will gnaw on bones and deer antlers to obtain calcium.
Pine or Woodland Vole (Microtus pinetorum)
This mammal builds a large network of subterranean tunnels where it caches food for the winter. It can be a serious agricultural pest when it girdles orchard trees in order to consume the bark during the winter months.
Woodland Jumping Mouse (Napaeozapus insignis)
A long tail and powerful hind legs provide this Pennsylvania native with the ability to jump six to eight feet when avoiding a predator. Its closest relative is the meadow jumping mouse and both are true hibernators.
Meadow Jumping Mouse (Zapus hudsonius)
This tiny rodent is reported to be an excellent swimmer.
Porcupine (Erethizon dorsatum)
Porcupines cannot throw their quills, but as the tail is swished violently to threaten an enemy, loosely attached quills may fall off the body. Young are born with soft, short quills that dry and stiffen within a few hours.
Gray Wolf (Canis lupus)
This species has been extirpated (disappeared) from Pennsylvania since about 1892. Stories about wolf kills persisted through the 1940s.
Gray Fox (Urocyon cinereoargenteus)
It is reported that this mammal can climb trees.
Red Fox (Vulpes vulpes)
The den of the red fox is frequently a converted woodchuck burrow that takes advantage of the multiple exits created by the original inhabitant. Red foxes will dig their own dens or make use of hollow logs as well.
Black Bear (Ursus americanus)
The black bear is not a true hibernator like the woodchuck. Although it goes through a period of dormancy, it does not lower its respiration, heart rate, or body temperature in the manner that defines true hibernation.
Raccoon (Procyon lotor)
Raccoons are highly adaptable and have become quite accustomed to life around people. During the last decade, its association with rabies in the Commonwealth has made it a less favored neighbor than might otherwise be the case.
Pine Marten (Martes americana)
Although this mammal was thought to have disappeared from the state around 1900 due to loss of forest habitat, two specimens have been collected in the latter half of the century. The Pennsylvania Biological Survey classifies its status as undetermined at present.
Fisher (Pekania pennanti)
This animal recently has been reintroduced in Pennsylvania. Tracking of the released individuals indicates that the fisher are doing well.
Ermine or Short-tailed Weasel (Mustela erminea)
In summer, the ermine is dark brown above and white washed with yellow below. In the winter, it turns completely white except for a black tip on the tail.
Spotted Skunk (Spilogale putorius)
This relative of the striped skunk is known to occur only in Fulton and Bedford counties in south-central Pennsylvania. It is the smallest skunk, averaging only 1-3 lbs. As with the striped skunk, the patterns of black and white vary greatly among individuals.
Lynx (Lynx canadensis)
Although there are records of lynx in the Commonwealth, it is believed that all are cases of this predator temporarily expanding its range due to low prey densities further north.
Bobcat (Lynx rufus)
This species is rarely observed because of its shy and elusive nature. Bounty was paid on bobcats in the Commonwealth between 1810 and 1938. Its numbers are currently considered to be low, and concern for the impact of development in regions of preferred habitat have caused it to be designated “vulnerable” by the Pennsylvania Biological Survey.