Mammals of Bombay Hook National Wildlife Refuge

Bombay Hook National Wildlife Refuges is located in coastal Delaware. The 15,978- acre refuge is relatively flat with most elevations less than ten feet above sea level. The major habitat type, consists of 13,100 acres, is tidal marsh intersected by winding rivers and creeks. Landward of the marsh are freshwater impoundments, timbered swamps, mixed deciduous woodlands, brushy thickets, grassy fields and croplands.

The variety of habitats provides essential food and cover requirements for an interesting combination of mammal species. Those most frequently seen, especially in the early morning and the late afternoon, are the cottontail rabbit, woodchuck, gray squirrel, and white-tail deer. Less commonly observed are the raccoon, skunk, opossum and red and gray foxes.

Because of a combination of small size, secretive habits, or nocturnal activity, many mammals are seldom seen. However, the careful observer will see tracks, trails, tunnels, burrows, nests and other signs that reveal their presence.

The following list of 35 species was prepared by Refuge personnel with the cooperation of Federick A. Ulmer, Jr. of the Philadelphia Zoological Garden. Order of listing, scientific names and common names are from Burt and Grossenheider (Peterson Series).

Opossum (Didelphis marsupialis). The only marsupial (young carried in pouch on belly of female) in North America. Commonly found in all sheltered habitats. Normally active only at night; therefore, while present, seldom seen on the Refuge. Eats fruit, vegetables, nuts, meat, eggs, insects, and carrion.

Masked Shrew (Sorex cinereus). In our area, the most common member of the Shrew family. Inhabits all land areas. Hunts for insects and other small animals day or night; eats more than its own body weight each day.

Shorttail Shrew (Blarina brevicauda). Most abundant in damp woods with thick leaf mold. Feeds on insects, worms, snails, and other invertebrates; saliva is poisonous. Has no external ears. Can be found in Finis Woods.

Least Shrew (Cryptotis parva). Found in open, grassy areas and marshes. Distinguished from other shrews by cinnamon color and short tail. Eats insects and other small animals.

Eastern Mole (Scalopus aquaticus). Inhabits its moist, upland soils where it tunnels its way under the surface. Active day and night in burrows where it eats worms, other insects, and some vegetable matter. Has naked tail, no external ears, and eyes covered with thin skin.

Starnose Mole (Condylura cristata). The only mammal with nose surrounded by finger-like, fleshy projections giving appearance of a star. Prefers low, wet ground where it burrows for insects, many of them aquatic. Often appears above ground.

Little Brown Myotis (Myotis lucifugus). Present during the warm months. Seen in flight at dusk near the woods and over the pools of the Refuge. Feeds on insects on the wing; flight is erratic.

Silver-haired Bat (Lasionycteris noctivagans). Found in swamps flying among the flooded trees and in forested areas. Look for it at Finis Pool. Flies high and fairly straight. Distinguished by blackish-brown color.

Eastern Pipistrel (Pipistrellus subflavus). Appears early on summer evenings. Flight is slow and erratic. Feeds on small insects. One of the smallest bats in this area. Yellowish to drab brown in color.

Big Brown Bat (Eptesicus fuscus). Distinguished by dark brown color and large size. One of our most common bats. Active on warm evenings. Feeds on insects, chiefly on beetles.

Red Bat (Lasiurus borealis). A common woodland bat that roosts in trees until deep dusk. Flight is steady and rapid. Usually feeds in pairs, flying over the same area and following the same route over and over. Rusty-red in color.

Hoary Bat (Lasiurus cinereus). The largest eastern bat, it is found in the woodlands; flies late, high, and solitary. Hangs in trees during day. Color is yellowish to mahogany brown.

Raccoon (Procyon lotor). Common in the woodlands, along the field edges, around the freshwater impoundments, and in the salt marsh. Most active at night, but also seen in the daytime. Identified by black mask over eyes and ringed tail. Omnivorous; eats anything available. Often dunks food in water (as a lubricant to aid I swallowing). Look for evidence (scat) on Boardwalk Trail over the Salt Marsh.

Longtail Weasel (Mustela frenata). Chiefly nocturnal. Feeds mostly on small mammals. Long slender body, long neck. A few are present in the upland areas of Bombay Hook.

Mink (Mustela vison). An excellent swimmer. Feeds on small mammals, frogs, and fish. An occasional mink may be found in the marsh or along the streams in the Refuge.

River Otter (Lutra canadensis). A large weasel-like animal with small ears and a broad snout, rich brown in color. An aquatic mammal; feeds on fish, frogs, and crayfish. Makes dens in banks with entrance below water. Lives in the Refuge impoundments, but can be seen also in Raymond Gut along the Boardwalk Trail.

Striped Skunk (Mephitis mephitis). Common in the upland areas at night. Recognized by its odor and its black body and white stripe. Omnivorous, feeding on insects, grubs, eggs, mice, berries, and carrion, beginning shortly after sundown and ending about sunrise.

Red Fox (Vulpes fulva). One of the most commonly seen mammals on the Refuge, usually along the edges of the road, but most active at dawn, dusk, and at night. Feeds on small animals, insects, berries, and other fruit. Usually reddish yellow with black legs and feet and a white tipped tail, but there are many color variations.

Gray Fox (Urocyon cinereoargenteus). Has been identified as a very rare inhabitant of the Refuge. Normally active only at night and is very secretive. Diet is mostly small animals.

Harbor Seal (Phoca vitulina). Occasionally sighted along Delaware Bay, at Port Mahon, and at the mouth of the Leipsic River. This is the common seal seen along this part of the Atlantic Coast.

Woodchuck (Marmota monax). Abundant. Also known as the Groundhog. Lives in deep burrows excavated in fields, woods, and along the impoundment dikes. Thick-bodied, short-legged, brown colored, this mammal is a vegetarian that hibernates from October to February.

Eastern Chipmunk (Tamias striatus). Lives among logs and stumps in the hardwood areas. Look for it in Finis and Bear Swamp woods. Solitary and feeds on seeds, bulbs, fruits, nuts, insects, and eggs. Runs with tail straight up.

Eastern Gray Squirrel (Sciurus carilinensis). Inhabits the oak and hickory woodlands that are most accessible to the public on the Bear Swamp Trail and at Finis Woods. Arboreal, rarely venturing far from trees, although it stores nuts and acorns in small holes, some of which germinate and grow into trees.

Southern Flying Squirrel (Glaucomys volans). Probably abundant, but hardly ever seen because it is totally nocturnal. Inhabits hollow trees to emerge only after darkness fills the wooded swamps. It glides from tree to tree on a flap of skin between its front and hind legs, and it feeds on seed, nuts, and insects.

Beaver (Castor Canadensis). First reported on the Refuge in 1938, it was re-discovered during the fall of 1977, after an absence of nearly twenty years. Presently it is common in Finis, upper Shearness, and Bear Swamp Pools. Look for Beaver-chewed trees on entering Bear Swamp Trail. A nocturnal animal, seldom seen in the day. It feeds on tree bark and uses felled trees to build dams and lodges.

White-footed Mouse (Peromyscus leucopus). Abundant in wooded and brushy areas. Very white belly. Once one built a nest in the brochure box on Boardwalk Trail.

Rice Rat (Oryzomys palustris). Common in the salt marsh areas. Chiefly nocturnal.

Feeds on green vegetation and seeds and nests above high water level.

Meadow Vole (Microtus pennsylvanicus). Abundant in grassy, upland fields and among the grasses of the salt marsh. A good swimmer, feeds on grasses, sedges, seeds, and grain. Is this what the Northern Harrier is looking for?

Pine Vole (Pitymys pinetorum). Tunnels through the carpet of leaf mold and loose soil on the forest floor, prefers deciduous forests, do would be found in along parts of Pearson Point Trail and Bear Swamp Trail.

Nutria (Myocastor coypus [Molina]). Discovered in freshwater impoundments in 2003. Nests among marsh plants or digs a burrow in stream banks above the waterline. This is a non-native, introduced species that destroys habitat and threatens native species. Efforts are being made to limit or eliminate it wherever possible.

Muskrat (Ondatra zibethica). Common in the freshwater impoundments and in the salt marsh. Its houses are frequently seen as mounds of reeds and grasses rising above the water level. Distinguished by a tail that is flattened side to side. Trapped for its pelt and favored as a delicacy in some parts of Delaware.

Norway Ray (Rattus norvegicus). Lives around buildings, grain fields, and marsh edges. Often moves into tidal debris along beaches. The common rat of cities, towns, farms, and open areas.

House Mouse (Mus musculus). Found about building and sometimes in weedy and grassy fields. This is the common mouse found nearly everywhere.

Meadow Jumping Mouse (Zapus hudsonius). Inhabits the grassy fields. Might be mistaken for frogs as they leap through the grass. Primarily nocturnal. Feeds on seeds, fruits, and insects.

Eastern Cottontail (Sylvilagus floridanus). Abundant. Lives in bushy areas and grassy fields. Often seen from the roads in the early morning and late afternoon. Often a delicacy for raptors such as the Red-tailed Hawk and carnivores such as the Red Fox.

White-tail Deer (Odocoileus vieginianus). Common in the uplands and along the marsh edges. Most active at early morning and evening. Herd on the Refuge has grown to more six hundred individuals and is stabilized by an annual hunting program.

Other species are probably present on the Refuge but have not yet been verified. Reports of additional species are welcome.