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Oregon Wildlife Species

Mammals

Oregon Mammals:    

Order Didelphimorphia
Opossums - Family Opossums
Virginia Opossom
Immature Virginia Opossum
-Oregon Fish and Wildlife-

Opossum Didelphis virginiana

In Oregon the opossum is considered an invasive species.

The Virginia Opossum is a cat-sized mammal with a pointed nose, unfurred, black, leathery ears with white edges; beady eyes; a hind foot with an opposable halux (big toe); and a naked scaly tail.

It was introduced in Oregon between 1910 and 1921. Populations were established in northwestern Oregon apparently from releases of animals brought to the state as pets or novelties.

Small streams, forest communities, and agricultural lands planted to a variety of crops are typical of many habitats occupied by Virginia Opossums in Oregon. They are active nocturnally, 2-3 hours after sunset, remaining active for 9 hours or more, depending on the season.

Order Rodentia
Mountain Beavers - Family Apolodontidae
Mountain Beaver
Mountain Beaver
-Wikipedia-

Mountain Beaver Aplodontia rufa

The Mountain Beaver is a medium-sized muskrat-like rodent often lacking a visible tail. However, the mountain beaver has an extremely short, fur-covered tail, and otherwise differs from the muskrat by possessing five-toed feet. It is dark brown with a small white spot at the base of each ear.

In Oregon it occurs in forested areas on the west slope of the Cascade Range west to the Pacific Ocean. It is absent from the interior valleys.

Beavers - Family Castoridae

Living with Beaver

Beaver
Beaver
-Oregon Fish and Wildlife-

American Beaver Castor canadensis

The beaver, the largest rodent in North America, commonly weighs in excess of 25 kg. The beaver is highly modified for aquatic life; the body is compact; the legs are short with unguiculate feet; the hind feed are webbed and the claws on the first and second toes are split and function in grooming; the ears and eyes are small; and the ears and nostrils are valvular. Underwater, membranes cover the eyes. The paddle-like tail is broad, scaly and nearly without hairs. The thick underfur is overlain with coarse guard hairs; overall, the pelage (coat) is dark brown dorsally (on its back) shading to a lighter brown ventrally (on it's undersides). The tail and feet are blackish brown. There is a single annual molt.

In Oregon the beaver occurs in suitable habitats throughout the state. It is almost always associated with riparian or lacustrine habitats bordered by a zone of trees, especially cottonwood and aspen, willow, alder and maple. Small streams with a constant flow of water that meander through relatively flat terrain in fertile valleys and are subject to being dammed seem especially productive of beavers.

They are powerful swimmers; propulsion is largely by use of the webbed hind feet and tail as the front feet are held close under the chin. The tail is also used to maneuver in the water. On land, the beaver is a clumsy waddler. Of all the beaver's behavioral characteristics, non, doubtlessly, is as legendary as its ability to cut trees for food or construction of dams and lodges. Beavers live in colonies composed of family groups usually consisting of a mated pair of adults, their yearlings, and their young-of-the-year, although occasionally groups may contain individuals over 24 months old other than the mated pair. Pairing is commonly considered monogamous and long term.

Beavers are most active in the evening or at night but they can sometimes be observed engaging in various activities at any hour. Beavers do not hibernate, although activity during winter may not be conspicuous because it is largely beneath the ice.

Porcupines - Family Erethizontidae
Porcupine
Porcupine
-Oregon Fish and Wildlife-

Common Porcupine Erethizon dorsatum

The porcupine is a large, short-legged rodent with up to 30,000 bared-tipped quills (modified hairs) covering the upper parts of the body and the dorsal and lateral surfaces of the tail. The quills are scattered among much longer, course guard hairs; the underfur is woolly. The quills are arranged in rows across the body, the longest quills are on the rum, the shortest on the face. Quills used in defense are replaced commencing about 10-42 days after loss. The overall color of the porcupine is dark brown or blackish. The front feet have four toes, the rear feet five; all have strong, curved claws. The soles are naked.

In Oregon, the porcupine is found throughout most of the state east of the Cascade Range. West of the Cascade it is found in only a few scattered localities. Porcupine attains its greatest abundance in mixed coniferous and hardwood forests.

Porcupines do not hibernate and are active throughout the year. Activity is mostly nocturnal or crepuscular, but those feeding in trees may be observed at any time as they usually do not retire do dens during the daylight hours. Some use is made of dens in winter.

Porcupines make a variety of vocalizations and sounds with the teeth, some which can be heard at considerable distance. They seemingly are intelligent and are able to learn quickly; they have good memories and especially remember being mistreated.

Nutria - Family Myocastoridae

Living with Nutria

Nutria
Nutria
-Oregon Fish and Wildlife-

Nutria Myocastor Coypus

In Oregon the nutria is considered an invasive species.

The nutria is a large rat-like semiaquatic rodent. The species has a hunched body; a round, nearly hairless tail; a valvular mouth and nose; and pentadactyl feet with naked soles. The toes of the hind feet, except for the hallux, are included in a web. As an adaption to the aquatic environment, the eyes, nostrils, and small ears are set high on the sides. The pelage consists of long, course guard hairs and soft, dense underfur. Overall, the color usually ranges from dark brown to yellow-brown. The muzzle is frosted with white hairs. The skull of the nutria is heavy and somewhat angular, like that of the porcupine.

Nutria are native to South America and were introduced deliberately into North America for fur farming in the 1930s. In Oregon the species is limited to areas in the southern Willamette Valley and central Coastal Region. It usually occurs in or adjacent to rivers, lakes, sloughs, marshes, ponds, and temporarily flooded fields.

They are active mostly at night, although individuals occasionally may be observed swimming, feeding or walking along a pond bank during the daylight hours, especially when nighttime temperatures are below freezing, and may be observed basking in the sun when temperatures are low.

Nutrias construct burrows in banks of rivers, sloughs, and ponds, sometimes causing considerable erosion. They build nesting platforms from matted vegetation which are used by maternal females with litters. They are gregarious, commonly forming groups of 2-13 individuals consisting of a male and female dominant over other individuals. Commonly the subordinate individuals are related. Adult males sometimes are solitary.

Glossary of terms | Sources: Atlas of Oregon Wildlife | Land Mammals of Oregon

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