Wildlife Habitat Management Institute 

Wetland Mammals

March 2001 Fish and Wildlife Habitat Management Leaflet Number 21 

National Oceanic and Atmospheric Administration 

Wetlands provide a diversity of productive habitats for 

mammals, birds and other wildlife. 

Wetland Basics 

Wetlands are those lands between aquatic and 

terrestrial environments. The U.S. Fish and Wildlife 

Service (Cowardin et al. 1979) described five major 

systems of wetlands and deepwater habitats: marine, 

estuarine, lacustrine (lakes), riverine (rivers and 

streams), and palustrine (marshes, swamps, and bogs). 

Marine and estuarine systems include coastal habitats, 

while the other three systems include most inland 

freshwater wetlands. At least 50% of the original 

wetland area in the continental United States has been 

lost to drainage, land-use development, and other 

human activities since colonial settlement. 

Water is the most influential component of wetland 

ecosystems, controlling soil characteristics and 

associated plant and animal life. Wetland substrates 

are inundated or saturated near the surface long enough 

during the growing season to influence the vegetation 

community. Plants that are adapted to tolerate wet 

environments (generally referred to as hydrophytes) 

are more likely to inhabit wetland systems than plants 

that favor upland sites. Hydric soils develop in 

wetlands, largely due to the anaerobic conditions 

created by saturation at or near the surface during the 

growing season. Therefore, wetland hydrology, 

hydrophytic vegetation, and hydric soils are the three 

basic characteristics of wetland habitats. 

Wetlands provide a variety of biological and socioeconomic functions, and are among the most 

productive ecosystems in the world. They provide 

diverse wildlife habitats and support complex food 

chains. At least 150 bird species and 200 fish species 

are wetland-dependent. About 900 terrestrial animal 

species use wetland habitats of the United States 

periodically throughout their lives for breeding, foraging, 

or other activities. The Prairie Pothole Region in the 

northern plains contains 10 percent of U.S. wetland 

area, but supports 50 percent of U.S. mallard, northern 

pintail, and green-winged teal production. The Great 

Basin area of the intermountain west also provides 

important wetland habitat for migrating birds. 

Many species of mammals depend on wetland habitats 

for survival. Some mammals are herbivores, while 

others are omnivores or carnivores that rely on varying 
Wetland Mammals 

Wetland Functions and Values 

Hydrological 

� Help control floodwater and lower flood and 

erosion potential. 

� Contribute to aquifer and groundwater recharge. 

Geochemical 

� Filter pollutants and heavy metals from precipitation and point source and non-point 

source pollution (agricultural runoff, industrial 

discharge, etc.). 

Biological

� Provide habitat for fish and wildlife.

Socio-economic

� Support timber production.

� Support shellfish production and aquaculture.

� Provide water sources for agriculture.

� Provide fuel source (peat) in some countries.

� Provide recreational opportunities such as

hunting, trapping, canoeing, and bird watching. 

� Provide educational opportunities. 

� Aesthetic values. 

combinations of aquatic invertebrates, amphibians, fish, 

and other prey. Many wetland mammals consume 

large numbers of insects, cultivate the soil, or modify 

habitat used by waterfowl and other wildlife. 

This leaflet is designed as an introduction to wetland 

mammal identification and management, and is intended 

to assist landowners in their efforts to effectively 

manage wetland mammal habitats. The success of 

any management strategy depends on targeting the 

specific needs of the desired species and analyzing 

designated habitat areas to ensure all required habitat 

elements are present. Not all habitat management 

recommendations are suitable for all wetlands. Most 

successful plans use a combination of management 

methods that improve wetland biodiversity. Individual 

plans should take into account local climate, flora, and 

fauna. Landowners should be familiar with state and 

federally listed plant and animal species (see U.S. Fish 

and Wildlife Service Endangered Species Homepage, 

http://engangered.fws.gov) and are encouraged to 

consult natural resource professionals to achieve 

management objectives and identify future goals. 

Wetland Mammals 

Wetlands throughout North America are used by a 

wide variety of mammals. However, some species 

are more closely associated with wetland habitats than 

others. This leaflet focuses on species considered 

wetland mammals by Neiring (1992) and Burt and 

Table 1. Species of wetland mammals in North America. 

Order Family name Species name 

Insectivora Soricidae Arctic shrew, masked shrew, Pacific shrew, 

Pacific water shrew, smoky shrew, water shrew 

Talpidae Star-nosed mole 

Rodentia Zapodidae Meadow jumping mouse 

Muridae* Cotton mouse, golden mouse, marsh rice rat, 

meadow vole, southern red-backed vole, water 

vole, muskrat, round-tailed muskrat, southern bog 

lemming 

Capromyidae Nutria 

Castoridae Beaver 

Lagomorpha Leporidae Marsh rabbit, swamp rabbit 

Carnivora Mustelidae Mink, river otter 

*Incorporates and replaces Cricetidae 

2 
Wetland Mammals 

USDA Natural Resources Conservation Service 

Tidal marshes provide numerous functions, including 

food chain support of coastal fisheries and habitat 

functions for mammals, birds, and other wildife. 

Grossenheider (1980). 

Wetland mammals inhabit a variety of wetland habitats, 

and have diverse food and cover requirements. Below 

are general descriptions of wetland mammals, tracks, 

ranges, and habitat associations. 

Shrews 

Shrews are small, mouse-size insectivores with long, 

pointed noses and small eyes. They are found 

throughout most of North America and are active yearround. Shrews require an enormous amount of food 

to fuel their fast metabolisms. They feed on insects, 

slugs, and other invertebrates, and small vertebrates 

such as salamanders, frogs, and other mammals. 

Predators such as snakes, hawks, owls, weasels, and 

foxes often rely heavily on shrews as a major diet 

component. Prolific breeders, most shrews can 

produce up to three litters a year, each litter containing 

two to ten young. Six species of North American 

shrews are closely associated with wetlands: the Arctic 

shrew, smoky shrew, water shrew, Pacific water shrew, 

Pacific shrew, and masked shrew. 

Moles 

Moles dig shallow and deep tunnel systems below the 

ground surface. The low ridge of pushed-up soil on 

the ground surface is a sign that moles are below foraging 

for food. The more permanent, deeper tunnels are 

Arctic shrew (Sorex arcticus) 

Total length: 10.1-12.6 cm (4-5 in.) 

Range: Most of Canada and Alaska south to North 

Dakota, northeast South Dakota, Minnesota, Wisconsin, and Michigan’s Upper Peninsula. 

Habitat: Swamps, bogs, marshes, and grass-sedge 

meadows. 

Arctic shrew from Burt and Grossenheider (1980). 

Smoky shrew (Sorex fumeus) 

Total length: 11-12.7 cm (4 1/4-5 in.) 

Range: Northeastern U.S. south through mountains to 

eastern Tennessee, north Georgia, and northern South 

Carolina; north to Ontario, Quebec, New Brunswick, and 

Nova Scotia. 

Habitat: Various types of moist wooded areas, swamps, 

and along streams. 

Comments: Uses tunnels made by red-backed voles, 

bog lemmings, northern short-tailed shrews, and starnosed moles. 

3
Wetland Mammals 

Water shrew (Sorex palustris) 

Total length: 14.4-15.8 cm (5 5/8-6 1/4 in.) 

Range: Most of Canada south through northeastern 

California, Utah, and isolated populations in the White 

Mountains of Arizona; central states to northeastern 

South Dakota, northern Minnesota, Wisconsin, and 

Michigan; New England south through the Appalachians to North Carolina. 

Habitat: Among boulders along mountain streams or 

in sphagnum moss around lakes. 

Comments: Semi-aquatic with large, broad hindfeet, 

slightly webbed between third and fourth toes; all toes 

have stiff hairs on the sides to increase swimming 

efficiency; fur traps air bubbles underwater for 

buoyancy. 

Pacific shrew (Sorex pacificus) 

Total length: 12.9-16 cm (5 1/8-6 1/4 in.) 

Range: Pacific Coast from southern Oregon to northern 

California. 

Habitat: Spruce and redwood forests; stands of alderskunk cabbage along the edges of streams. 

Comments: Nocturnal. 

Pacific water shrew (Sorex bendirii) 

Total length: 14.7-17.4 cm (5 7/8-6 7/8 in.) 

Range: Coastal northern California north to southeastern British Columbia. 

Habitat: Marshes, along streams, occasionally moist forests. 

Comments: Largest Sorex species; fringed hairs on toes 

give it buoyancy to run on top of the water’s surface for 

several seconds; also dives. 

Masked shrew (Sorex cinereus) 

Total length: 7.5-11 cm (3-4 1/4 in.) 

Range: Most of northern North America south to Washington, Idaho, south-central Utah, north-central New 

Mexico, Nebraska, Iowa, Indiana, Extreme northern Kentucky, Maryland and south through the Applachians. 

Habitat: Marshes, moist fields, bogs, moist or dry woods. 

Comments: Primarily nocturnal, rarely seen. 

Masked shrew from Burt and Grossenheider (1980). 

4
Wetland Mammals 

used for resting, raising young, and food storage. 

Moles have broad, spade-like forefeet that are used 

for moving soil. The eyes are tiny and external ears 

are nonexistent. Moles eat a variety of insects and 

other invertebrates, and are typically important prey 

for raptors, snakes, owls, weasels, foxes, and other 

carnivores. Most moles live in well-drained upland 

areas. However, one species, the star-nosed mole, is 

adapted to living in the muddy soils of wetlands. The 

fleshy appendages on its nose enable it to recognize 

prey items by touch. 

Mice, rats, lemmings, and voles 

Mice, rats, lemmings, and voles are small to mediumsize rodents. Most live on or under the ground, and 

some are semi-aquatic. Lemmings and voles have 

Star-nosed mole (Condylura cristata) 

Total length: 15.2-21.1 cm (5 7/8-8 1/4 in.) 

Range: Most of the northeastern U.S.; southeastern 

Labrador south through most of Minnesota, northeastern Indiana, northern Ohio, south through the Appalachians and along coastal Virginia; isloated populations 

along Georgia coast. 

Habitat: Swamps, wet woods or fields, sometimes moist 

lawns. 

Comments: The only semi-aquatic mole; 22 tentaclelike, fleshy projections around tip of nose that act as 

tactile organs to probe/search out prey; waterproof fur, 

uses spade-like feet as paddles, tail as rudder; hunts 

stream bottoms for aquatic invertebrates, crustaceans, 

mollusks, even small fish; forages in tunnels for terrestrial invertebrates. 

Dr. Ken Catania, Vanderbilt University 

The fleshy, tentacle-like projections around the nose of 

the star-nosed mole are used for tactile detection of prey. 

short tails and small ears and eyes in contrast with the 

longer, thinner tails and larger ears and eyes of mice 

and rats. These rodents are active year-round and 

are primarily nocturnal. They feed on a variety of foods 

from subterranean fungus, seeds, fruits and green 

vegetation, to terrestrial and aquatic invertebrates, to 

small bird eggs and young. Mice, rats, lemmings, and 

voles are important prey for many predators including 

owls, hawks, raccoons, foxes, mink, weasels, skunks, 

and others. The number of litters and the number of 

young per litter vary among species. Several species 

of mice, voles, and the southern bog lemming are 

considered wetland species in North America. 

CVIOG/GeorgiaInfo 

The cotton mouse is a strong swimmer that inhabits moist 

woodlands, swamps, and other wetland areas. 

5
Wetland Mammals 

Cotton mouse (Peromyscus gossypinus) 

Total length: 15.2-20.5 cm (6-8 1/8 in.) 

Range: Southeastern U.S. from eastern Texas and southeastern Oklahoma east to southeastern Virginia, eastern 

North Carolina, eastern South Carolina, Georgia, and 

Florida. 

Habitat: Swamps, moist woodlands, beaches, rocky areas and brushlands. 

Comments: Strong swimmers and regularly climb trees; 

nocturnal. 

Marsh rice rat (Oryzomys palustris) 

Total length: 18.7-30.5 cm (7 3/8-12 in.) 

Range: Mostly the southeastern U.S.; eastern Texas 

north to southeastern Kansas, southeastern Missouri, 

southern Illinois, southern Kentucky, eastern North Carolina, and north to southeastern Pennsylvania and southern New Jersey. 

Habitat: Mostly marshes. 

Comments: Semi-aquatic and swims underwater; water 

repellant fur; small internal cheek pouches; 

nean fungus Endogone is an important diet component. 

Mansell 1998. 

subterraCVIOG/GeorgiaInfo 

Meadow vole (Microtus pennsylvanicus) 

Total length: 14-19.5 cm (5 1/2-7 3/4 in.) 

Range: Canada and Alaska (except northern most 

portions) south and east to northern Washington, 

Idaho, Utah, New Mexico, Wyoming, Nebraska, 

northern Missouri, northern Illinois, Kentucky, 

northeastern Georgia, and South Carolina. 

Habitat: Marshes, swamps, woodland glades, 

mountaintops, fields. 

Comments: Active day or night; good swimmer, nests 

above or below ground. 

Meadow jumping mouse (Zapus hudsonius) 

Total length: 18.7-25.5 cm (7 1/4-10 in.) 

Range: Southern Alaska and most southern portions of 

Canadian provinces; northeastern U.S. west to eastern 

Wyoming and south to northeastern Oklahoma and northeastern Georgia. 

Habitat: Moist fields, marshes, brushy fields, woodlands 

with thick vegetation. 

Comments: Belongs to the family of jumping mice, 

Zapodidae; primarily nocturnal; Hibernates in winter nest 

two to three feet below ground surface, October or November; emerges from hibernation in April or May; can 

take jumps three to four feet long on large hindfeet; feeds 

mostly on invertebrates in spring, seeds and green plants, 

and the subterranean fungus Endogone in summer and 

fall. 

6
Wetland Mammals 

Golden mouse (Ochrotomys nuttali) 

Total length: 15-19 cm (5 7/8-7 1/2in.) 

Range: Eastern Texas and Oklahoma, southern Missouri 

and southern Illinois to the East Coast; southern Virginia 

south to central Florida. 

Habitat: Swamps, greenbrier thickets, rocky hemlock 

slopes. 

Comments: Arboreal mouse, uses long tail for balance; 

bright golden-cinnamon color with white belly. 

Mansell 1998. 

Southern red-backed vole (Clethrionomys gapperi) 

Total length: 12-15.8 cm (4 3/4-6 1/4 in.) 

Range: Southern portion of most Canadian provinces 

south into Oregon; Rocky Mountain system to Arizona 

and New Mexico; 

Wisconsin, northern Michigan; Allegheny Mountain 

system to North Carolina, New England south to Maryland. 

Habitat: Cool, damp forests; swamps and bogs. 

Comments: Active day and night; usually uses natural 

runways along fallen logs, tree roots, along rocks or tunnels of other animals; climbs trees. 

CVIOG/GeorgiaInfo 

North and South Dakota, Minnesota, 

Water vole ( Arvicola richardsoni) 

Total length: 19.8-26.1 cm (7 3/4-10 1/4 in.) 

Range: Southeastern and southwestern British Columbia and southwestern Alberta south through central and 

eastern Washington; central and eastern Oregon, northern Idaho, north-central Utah and western Wyoming. 

Habitat: Upland creek- and streambanks and marshes; 

often above timberline. 

Comments: Large, semi-aquatic vole; burrows along 

streambanks and lives in colonies. 

Southern bog lemming (Synaptomys cooperi) 

Total length: 11.8-15.4 cm (4 5/8-6 1/8 in.) 

Range: Southeastern Manitoba east to Newfoundland 

and south to Kansas, northeastern Arkanses, western 

North Carolina, and northeastern Virginia. 

Habitat: Low, damp bogs and meadows with heavy vegetation. 

Comments: Active day or night; uses underground runways of other small animals; also burrows 

inches underground to create own system of tunnels. 

about six 

Muskrats 

Muskrats are active year round, and feed on emergent 

wetland plants including the roots and shoots of cattails, 

arrowheads, duck potato, bur reed, bulrushes, 

pondweed, or other aquatic vegetation. Corn, clover, 

alfalfa, carrots, apples, insects, and aquatic 

invertebrates are also eaten. Muskrats do not cache 

food for the winter. Instead, they dig up roots and 

tubers from under the ice in cold regions, creating visible 

“push-ups” — mounds of ice that are visible on the 

surface of the ice. During warmer months, feeding 

stations are usually within 200 yards of the cone7 
Wetland Mammals 

Muskrat (Ondatra zibethicus) 

Total length: 40.9-62 cm (16 1/8-24 3/8 in.)] 

Mansell 1998. 

Range: Most of U.S. and Canada; except for extreme 

southern U.S. and arctic regions of Canada. 

Habitat: Marshes, edges of ponds, lakes, rivers, and 

streams; brackish or saltwater waterways; dislike strong 

currents. 

Comments: Aquatic rodents; hindfeet partially webbed 

and vertically flattened, long scaly tail used for swimming; build conical houses of marsh vegetation two to 

three feet above the surface of the water; houses usually have one nesting chamber with one or more underwater entrance; several muskrats may live in one house 

during cold months; also burrows into banks of streams 

and ponds; valuable fur bearer. 

CVIOG/GeorgiaInfo 

snapping turtles, large snakes and fish, and some 

raptors. 

Muskrats have a valvular mouth that allows them to 

feed underwater. The dense pelage of nearly 

waterproof underfur overtopped with longer, coarse 

guard hairs provides insulation. Muskrats have glands 

under the skin near the anus that produce a musky 

odor, especially during the breeding season. These 

aquatic rodents can have two or three litters per year, 

averaging six young per litter. Females with young 

can be aggressive and territorial. 

Rabbits 

Swamp rabbits and marsh rabbits are similar to their 

upland cottontail cousins, but are associated with 

bottomland hardwood wetlands and coastal marshes 

of the Southeast. Feeding on a variety of wetland and 

upland plants, these species are popular game animals 

in many areas. They are also an important food source 

for many carnivores associated with bottomland 

hardwood and coastal wetlands including alligators, 

snakes, raptors, bobcats, and foxes. Being strong 

swimmers, both species readily take to water to escape 

from predators. 

Marsh rabbit (Sylvilagus palustris) 

Total length: 35-45 cm (14 1/8-18 in.) 

Range: Southeastern Virginia southwest to Florida. 

Habitat: Wet bottomlands, swamps, hummocks, lake borders, coastal waterways. 

Comments: Primarily nocturnal; takes to water when 

threatened, good swimmer. 

shaped house/den, which is built of vegetation above 

the water’s surface. Some dig burrows and nest 

chambers in streambanks with entrances below the 

water level. Runs created through wetland vegetation 

may be visible on the bottom of shallow marshes, 

streams, or other frequently used areas. Muskrat 

predators include mink, red foxes, raccoons, bobcats, 

8 
Wetland Mammals 

Swamp rabbit (Sylvilagus aquaticus) 

Total length: 53-54 cm (20 7/8-21 1/4 in.) 

Range: Eastern Texas and eastern Oklahoma east to 

southern Illinois and northern Georgia. 

Habitat: Swamps, marshes, wet bottomlands, canebreaks. 

Comments: Also called cane-cutter rabbit; can do damage to agricultural crops near swamps; good swimmer 

and swims as regular mode of locomotion; runs circles in 

front of hunting dogs; rarely burrows. 

Mike Haramis, USGS Patuxent Wildlife Research Center 

The foraging and tunneling activity of nutria can 

severely degrade sensitive coastal marshes. 

and streams. Nutria feed mostly at night, but are also 

active during daylight hours. Besides humans, alligators, 

and raptors, there are few natural predators to control 

nutria numbers. 

The foraging and burrowing activities of nutria can 

destroy wetland vegetation, degrade native wetland 

ecosystems, and damage human economic interests. 

Mansell 1998. CVIOG/GeorgiaInfo 

Nutria 

Nutria are semi-aquatic, primarily herbivorous South 

American rodents that were introduced in North 

America in 1899 by California fur producers. 

Eventually, nutria escaped or were introduced in 22 

states across the U.S. Nutria are smaller than beavers, 

but larger than muskrats. Under optimal habitat 

conditions, female nutria born during the summer can 

reach sexual maturity at four months of age. They are 

prolific breeders and may have two or three litters per 

year, each litter averaging four to five young. Nutria 

are considered habitat generalists because they are 

common where they are established and inhabit a 

variety of habitats, including coastal and inland 

freshwater and brackish marshes, bottomland 

hardwood forests, lagoons, swamps, drainage canals, 

freshwater impoundments, and banks of lakes, rivers, 

Nutria (Myocastor coypus) 

Total length: 67-140 cm (26 3/8-55 1/8 in.) 

Range: Introduced in the Southeast from South 

America; also in Maryland, southern New Jersey, scattered in the Great Plains, northern Oregon, and Washington. 

Habitat: Marshes, swamps, ponds, and lakes. 

Comments: Also known as Coypu, incisors dark-orange and protrude beyond lips; 

feeds on available aquatic vegetation, eats at feeding 

station (log, vegetation, other raised object); 

builds nest of vegetation on surface of water; rarely 

burrows into banks to nest. 

Nutria with kits. 

Mike Haramis, USGS Patuxent Wildlife Research Center 

Primarily nocturnal, 

typically 

9
Wetland Mammals 

They consume the basal portions of plants, including 

roots, rhizomes, and tubers. During the winter months, 

nutria may feeds on the bark of willows, bald cypress, 

or other bottomland hardwood species. Nutria also 

eat agricultural crops adjacent to aquatic habitats such 

as sugarcane, rice, grain sorghum, and ornamental 

plantings. Native muskrats consume only the stems of 

aquatic plants, but nutria typically excavate the entire 

plant leaving little chance for regrowth. The cut stems 

may be used to build feeding stations. Their foraging 

activities destroy the root mat that is so important to 

soil stabilization in aquatic ecosystems. Without the 

root mat, erosion increases and vegetated marsh is 

converted into open water degrading the marsh habitat 

required by many wildlife species, and wetland 

vegetation regrowth is inadequate or nonexistent. 

These open areas, void of vegetation caused by 

foraging activities, are called “eatouts” and can result 

in permanent marsh loss. Burrowing activities can 

damage dikes, levees, and other water control 

structures. Nutria can also outcompete and displace 

native muskrat populations. 

Beaver 

Beavers are the largest living rodents in North America. 

Beavers are active year-round, mostly at night. The 

most obvious characteristic is the flat, paddle-like tail 

that is used for temperature regulation, fat storage, and 

for communication (during alarm situations). The scaly 

tail is also used as a rudder while swimming and for 

balance when cutting trees. The ears, nose, and mouth 

are valvular for underwater activities. A nictitating 

membrane covers the eyes for clear, underwater vision. 

Specialized toes on the hindfeet comb the fur and 

distribute water-repellent oil from two abdominal oil 

glands. Large castor (anal scent) glands produce 

castoreum, a yellowish-brown oil that is deposited on 

mud scent mounds to mark territory. Scent mounds 

are generally close to the water’s edge and have a 

pungent smell. Family groups typically contain paired 

adults, three or four kits, and yearlings residing in one 

lodge or burrow. At the age of two years, young 

beavers are driven out of the family lodge and territory. 

Females can breed at 1 1/2 years of age. C. Rewa 

Mansell 1998. 

Beaver (Castor canadensis) 

Total length: 90-117 cm (35 1/2-46 in.) 

Range: Most of Canada and the U.S. except for most of 

Florida and Nevada, and southern California. 

Habitat: Rivers, streams, marshes, lakes, and ponds. 

Comments: Beavers inhabiting faster moving rivers and 

streams burrow into the banks to create chambers with 

underwater entrances; others build stick-and-mud dams 

across streams and large conical lodges of sticks and 

mud at the water’s edge (one or more underwater entrances); wood chips on floor absorb moisture, vent near 

top of lodge provides fresh air. 

CVIOG/GeorgiaInfo 

Beaver manipulate wetland vegetation and hydrology by 

cutting trees for building dams on streams. 

10
Wetland Mammals 

C. Rewa 

Beaver dams can enhance habitat for some wildlife by 

increasing water depth and aqautic invertebrate production. 

Beavers inhabit wooded lakes, streams, and rivers 

throughout much of North America. Beavers prefer 

the bark and green twigs of aspen, poplar, birch, maple, 

sweetgum, blackgum, black cherry, tulip poplar, and 

willow trees. Leaves and roots of woody plants are 

consumed along with grasses, sedges, and rushes 

during the summer. They use woody materials to build 

stick-and-mud dams, lodges, and underwater winter 

food caches. 

The waterproof underfur is covered by long, dark 

brown guard hairs. Prime beaver pelts were the 

backbone of the fur trade in colonial times. 

Overharvesting almost caused the beaver’s extinction. 

Repatriation of beavers to their former range, 

establishment of bag limits, and falling fur prices helped 

re-establish beaver populations in much of their former 

range. 

Mink 

The mink is a semi-aquatic member of the weasel family 

(Mustelidae). Mink were the first American furbearers 

to be raised in captivity for their pelts. Elongated 

bodies and waterproof fur allow the mink to swim easily 

and feed on crayfish, frogs, and fish. Mink also prey 

on small mammals, birds, and eggs. When the mink is 

threatened or disturbed, it releases musk from scent 

glands located in the anal region. The musk, along 

with droppings, is also used to mark territory on 

waterways. Mink are typically solitary and are 

primarily nocturnal. 

Mink (Mustela vison) 

Total length: 49.1-72 cm (19 1/4-28 1/4 inches) 

Range: Most of United States and Canada except Arizona, southern California, southern Utah, southern New 

Mexico, and western Texas. 

Habitat: Along rivers, streams, lakes, ponds, and 

marshes. 

Comments: Primarily nocturnal; males larger than females; both sexes can be hostile to intruders; one of the 

most valuable fur animals; rich dark brown, usually with 

a white chin patch; eyes are yellowish-green; male pelts 

usually worth more than female pelts because they are 

larger. 

River otter 

River otters are sociable, semi-aquatic members of 

the weasel family. Webbed feet and clawed toes, along 

CVIOG/GeorgiaInfo 

River otter (Lutra canadensis) 

Total length: 88.9-131.3 cm (35-51 5/8 inches) 

Range: Alaska, most of Canada south to northern California and northern Utah; Newfoundland south to Florida; 

extirpated from most of Midwest. 

Habitat: Rivers, ponds, lakes, streams in wooded areas, 

but has been known to travel far from water. 

Comments: Males larger than females; active during the 

day if isolated from human disturbance. 

11
Wetland Mammals 

with a streamlined body and thick, tapered tail, help 

river otters move swiftly underwater. Fish, crayfish, 

frogs, salamanders, snails, turtles, snakes, small birds, 

and some vegetation make up the river otter’s diet. 

Otters are chiefly nocturnal, but can be seen during 

the day playing with each other or their food. Slides 

are smooth grass-, mud- or snow-covered slopes at 

the water’s edge up to 25 feet long that river otters 

use repeatedly. Otters typically have 1-5 kits that stay 

with the parents for as long as one year. Dense, oily 

underfur limits the market value of river otter pelts. 

Other mammals 

Other mammals such as raccoons, black bears, whitetailed deer, and moose use wetlands extensively, but 

also rely on a variety of upland habitats. Raccoons 

are associated with forests, wooded swamps, streams, 

and lakes. Black bears may wade into lakes and 

streams to catch an occasional fish (black bears eat 

mostly vegetable matter). White-tailed deer are 

generally considered an upland species, but find food 

and cover in wetland habitats. Moose feed on 

submerged wetland vegetation, and use water as an 

escape from biting insects. Moose are typically found 

in spruce forests and aspen and willow thickets close 

to water. 

Ruth Nissan, USFWS 

Shorebirds like the black-necked stilt, wading birds, and 

waterfowl can benefit from vegetation management and 

water level manipulation conducted to improve wetland 

mammal habitat. 

Raccoon, black bear, white-tailed deer, and moose are 

some upland mammals that are also associated with 

wetland habitats. 

Habitat Management for Wetland Mammals 

Habitat management practices applied to a particular 

wetland depends on the goals of the landowner or 

manager. Management efforts can be directed toward 

a specific wildlife species, or aimed at increasing the 

overall biodiversity of wetlands and associated upland 

habitats. Successful efforts usually increase seed 

sources, invertebrate populations (an important food 

source for waterfowl and other birds, small mammals, 

fish, and amphibians) and other wetland mammal foods. 

Management efforts should also address the cover 

needs of targeted species. 

Wetland mammal habitat management typically 

involves manipulating the hydrologic condition 

(defined as the rate and timing of inflow and outflow, 

source, duration, frequency, and depth of flooding, 

ponding, or saturation), hydrophytic plant 

communities, and/or other habitat components. Many 

factors affect management practices including: 

� topography, shape, and size of the wetland; 

� water quality, depth, and natural/controlled fluctuating water level; 

� soil characteristics (especially if plantings are a 

consideration); 

� local climate; 

� existing and desired vegetation species, composition, and structure; 

� existing wildlife species and populations; and 

12
Wetland Mammals 

� condition and management of associated upland 

habitats. 

Managers should consider how proposed management 

actions would affect the following topics before taking 

action: 

• impact on existing wetland functions; 

• change in plant growth rate or composition 

due to changes in volume of available water; 

• effects on downstream flows, associated wetlands, and other water-related resources; 

• effects on water temperature as related to plant 

growth or fish and wildlife populations; 

• effects of management on non-target fish and 

wildlife species, and threatened and endangered species; 

• effects of livestock grazing on run-off, infiltration, and wetland vegetation; and 

• value of adjacent wetlands or bodies of water 

that contribute to the wetland system complexity and diversity, decrease habitat fragmentation, and maximize use of the site by 

wetland associated wildlife. 

Physical habitat management practices such as disking, 

mowing, and prescribed burning should be avoided 

during the nesting and brooding season (March to 

August). Landowners and managers should consult 

wetland and wildlife professionals to decide on the 

most appropriate course of action to meet habitat 

management objectives. 

Water level management 

Providing a variety of water depths can maximize food 

and cover for wetland mammals and other wildlife. 

Natural water cycles depend on how close the water 

table is to the surface, natural inflow/outflow sources 

such as streams and rivers, and seasonal water 

fluctuations. Irregular, gently rolling topography helps 

create varying water depths that suit plant species with 

different levels of water tolerance, and habitat needs 

for invertebrates, waterfowl and other birds, 

amphibians, fish, reptiles, and wetland mammals. 

In natural wetland systems, water levels may fluctuate 

seasonally, providing a variety of hydrologic condiG. Kramer 

Drop-log inlets and other water control structures can be 

installed to enable managers to manipulate water levels 

on restored and created wetlands. 

tions throughout the year. Tidal wetlands typically have 

regular, daily fluctuations, with greater fluctuations associated with storms and monthly spring tides. When 

possible, wetland hydrology management practices 

should support or mimic these natural cycles. 

Water control structures are commonly used to create 

and restore wetlands by artificially manipulating water 

levels. In addition, a variety of water depths can be 

established by creating surface contours and 

microtopographic relief with construction equipment 

during the wetland creation or restoration process. The 

best time to manipulate surface contours is before hyC. Rewa 

Surface contours can be excavated during the wetland 

restoration process to increase the diversity of water 

depths and associated wetland vegetation. 

13
Wetland Mammals 

drology is returned to wetlands being restored or when 

water levels are artificially drawn down. 

Disturbing the hydrology of naturally functioning wetland systems is not usually recommended. Landowners and managers should consult federal, state, and 

local wetland regulatory authorities before manipulating wetland hydrology. 

Vegetation management 

When used in combination with other methods of vegetation management, water level manipulation can significantly influence vegetation composition and associated wildlife. High water levels, resulting from natural flood cycles or managed flooding, can be used to 

control undesirable vegetation or help reduce high 

wetland herbivore populations. Lowering water levels can stimulate germination of emergent wetland 

plants. Reflooding abandoned beaver ponds can also 

rejuvenate some wetland vegetation and increase 

biodiversity. 

Disking is a mechanical method used to control or 

break up dense stands of undesirable vegetation on 

managed wetlands. Some managed wetlands can be 

drained, disked, and then reflooded. Disking benefits 

wetland vegetation because it aerates the soil and exposes drained soils to sunlight, which stimulates germination of moist soil plant seeds and invertebrate production. The entire process is generally conducted on 

Jim and Karen Hollingsworth, USFWS 

Muskrats can reduce dense stands of emergent wetland 

vegetation. High muskrat populations can also cause 

eatouts, leaving wetland habitats temporarily void of 

emergent vegetation. 

annual, 3-year, or 5-year intervals, depending on management goals. Other management practices may accompany disking to achieve a specific management 

objective, such as prescribed burning or mowing to 

control invading woody species. 

In some situations, prescribed burning can be used to 

reduce emergent vegetation and revert plant communities back to earlier successional stages. New growth 

stimulated by fire attracts a variety of wildlife. When 

used in combination with disking or mowing, prescribed burning can be an effective habitat management tool. Benefits of prescribed burning on herbaceous wetlands may include: 

� reducing dense or impenetrable stands of undesirable vegetation; 

� exposing seed for wildlife use; 

� improving soil conditions for seeds and stimulating germination; 

� stimulating vegetation growth used as wildlife 

food and cover; 

� opening up dense stands of vegetation for 

waterfowl movement; and 

� helping control woody vegetation and invasive species. 

Prescribed burning should be conducted under proper 

weather conditions and under the supervision of licensed personnel. Water control structures help regulate water flow before and after burning. Burning 

should be avoided during the nesting season (March 

to August) and during times of drought. 

Plantings can increase the amount of desirable vegetation in newly created or restored wetlands, and in 

wetlands dominated by undesirable vegetation. However, planting vegetation can be expensive and timeconsuming. Undesirable plant species may need to be 

removed before planting desirable species to help ensure success. 

Other vegetation management methods include mowing, prescribed grazing, and managing wildlife species 

that have the ability to alter habitat, such as beavers 

and muskrats. Muskrats can open up dense stands of 

cattails. Openings created by muskrat foraging can 

make emergent wetlands more attractive to waterfowl, 

14
Wetland Mammals 

The following is a list of possible management actions to enhance habitat value for wetland mammals. NRCS 

Conservation Practices and various programs that may provide financial or technical assistance to carry out 

specific managment practices are listed where applicable. 

Habitat 

component 

Management options for increasing 

habitat quality or availability 

Conservation practices 

and assistance programs* 

Food Restore natural wetland hydrology and vegetation 

in previously converted or degraded wetlands. 

657 

WRP, PFW 

Protect coastal and freshwater wetlands, marshes, 

lakes, and ponds from siltation and non-point 

source pollution by establishing conservation 

buffers, controlling livestock access, and providing 

bank stabilization through vegetation plantings. 

393, 643, 657 

WRP, WHIP, EQIP, 

PFW, CRP 

Reduce herbicide use on wetlands and adjacent 

uplands where application results in reduction of 

invertebrates (terrestrial or aquatic). 

Cover Protect existing wetlands and restore natural 

wetland hydrology and vegetation to previously 

converted or degraded wetlands. 

657 

WRP, PFW 

Allow vegetation to grow in grassland meadows 

and prairies and conduct appropriate grassland 

management practices such as prescribed burning, 

managed grazing, and rotational mowing. 

327, 338, 528A, 644, 645 

WHIP, EQIP, PFW 

Manage water levels to provide a variety of water 

depths and associated wetland vegetation structure. 

Increase surface contour diversity by excavating 

small swales, islands, and level channels prior to 

re-establishing hydrology in restored wetlands or 

during the draw-down phase of managed wetlands. 

657 

WRP, PFW 

Establish conservation cover on adjacent croplands 

and other disturbed areas and initiate rotational 

grazing on surrounding grazing lands. 

327, 528A, 647 

CRP, EQIP 

Habitat 

interspersion 

Combine above prescriptions to increase 

interspersion of habitat components and amount 

of suitable habitat. 

* See table on page 18 for a description of assistance programs. 

especially where the ratio of vegetation to open water 

is maintained at around 50:50 with good interspersion 

throughout. 

In general, grazing should be restricted in riparian areas through fencing or other means. Maintaining or 

expanding riparian buffer zones along streams and other 

waterways, or around lakes, ponds, and other bodies 

of water increases the amount and availability of wildlife habitat. 

Glyphosphate-based herbicides formulated for use on 

wetland vegetation (e.g., Rodeo� — reference to products does not imply endorsement) have been used to 

NRCS Conservation Practices 

that may be 

useful in 

undertaking the 

above management actions. 

Conservation Practice Code 

Conservation Cover 327 

Prescribed Burning 338 

Riparian Forest Buffer 391 

Filter Strip 393 

Prescribed Grazing 528A 

Restoration & Management 

of Declining Habitats 

643 

Wetland Wildlife Habitat 

Management 

644 

Upland Wildlife Management 645 

Early Successional Habitat 

Development 

647 

Wetland Restoration 657 

15
Wetland Mammals 

Effects of Beaver Activity 

Benefits of beaver ponds: 

• Enhance habitat for a variety of wildlife such as cavity-nesting waterfowl and other nesting birds 

(trees killed by flooding support nests of herons, egrets, ospreys, and other birds), aquatic invertebrates, reptiles, amphibians, and other wetland mammals. 

• Improve warm water fish habitat by increasing water depth and water temperature thereby increasing 

aquatic invertebrate food production. Note: Habitat for cold water fish (e.g., trout) downstream of 

beaver ponds may be compromised by increasing water temperatures and restricting upstream movements. 

• Provide suitable nesting, brood-rearing, foraging, and migration habitat for waterfowl, shorebirds, 

wading birds, and other birds. 

• Reduce water velocity and eroding potential of streams. 

• Reduce peak and frequency of flooding. 

• Provide fertile substrate for new herbaceous growth when area is abandoned by beavers or pond is 

permanently drained. 

In general, beaver activities establish, maintain, and enhance affected wetland habitats. However, there are 

cases when beaver activity results in inundation of roads or economically valuable areas. Beavers typically 

try to plug up what they perceive as “leaks” in water control structures, culverts, and drain pipes. These 

structures plugged by beavers can result in flooding and damage to roadways, agricultural fields, dwellings, 

timber, and other property. Southeastern states have experienced extensive timber damage caused by 

tree-cutting and flooding by beavers, especially in bottomland hardwood stands. Use of beaver pond 

levelers (see box on next page) and other measures can minimize economic losses associated with beaver 

activity. 

CVIOG/GeorgiaInfo 

The eastern newt and other amphibians can benefit from 

vegetation management and water level manipulation 

directed at wetland mammal management. 

control Phragmites and other invasive plants. However, herbicides are not generally recommended to 

control wetland vegetation because most are not species-specific. More importantly, herbicides can have 

negative effects on some aquatic life and ecosystems, 

and the toxic effects of many herbicides remain unknown. 

Environmental Effects of Wetland Mammal 

Activity 

Wetland mammals can affect wetland habitats in a 

variety of ways. Herbivores such as beavers, nutria, 

and muskrats can significantly alter vegetation structure 

and composition, while omnivores and carnivores can 

affect small mammal and invertebrate populations. 

Ground-dwelling mammals, like the star-nosed mole 

and various vole species, can aerate soil but can also 

16
Wetland Mammals 

CVIOG/GeorgiaInfo 

While not considered a wetland mammal, white-tailed 

deer frequently use shrub swamps, forested wetlands, and 

other wetland habitats. In northern areas, dense stands 

of conifer trees in and around wetland areas provide 

thermal cover for deer during winter. 

limit root and plant growth as a result of their foraging 

activities. Mink can affect upland nesting waterfowl, 

eggs, and young. 

Damage Prevention and Control Methods 

High densities of some wetland mammals can create 

challenges for wetland owners and managers. 

Landowners are encouraged to enroll the help of local 

animal damage control agents and wildlife or natural 

resource professionals to help correctly identify 

problem species and control methods. For detailed 

information on population control methods and speciesspecific signs of damage, see Prevention and Control 

of Wildlife Damage—1994 (Hyngstrom et al. 1994). 

Trapping can be an efficient and economical method 

to control overabundant populations of wetland 

mammals or problem individuals. Hunting and trapping 

regulations are available through state fish and wildlife 

The Clemson Beaver Pond Leveler 

The Clemson Beaver Pond Leveler was designed to: 1) reduce problem flooding in agricultural and timber lands, and 2) 

maintain and/or improve some benefits resulting from beaver ponds. 

flow, and the probability that the resident beavers will try to plug up the “leak,” minimizing dam construction. 

information about The Clemson Beaver Pond Leveler, contact Dr. Gene W. Wood, Mr. Larry A. Woodward, or Dr. Greg 

Yarrow at the Department of Aquaculture, Fisheries, and Wildlife, G08 Lehotsky Hall, Clemson University, Clemson, 

South Carolina, 29634 or by phone at (803) 656-3117. 

The pond leveler minimizes the sound of current 

For more 

17
Wetland Mammals 

Programs that provide technical and financial assistance to develop fish and wildlife habitat on private lands. 

Program Land eligibility Type of assistance Contact 

Conservation Reserve 

Program 

(CRP) 

Highly erodible land, 

wetland and certain 

other lands with cropping 

history. Stream-side 

areas in pasture land. 

50% cost-share for est. permanent 

cover and conservation practices, and 

annual rental payments for land enrolled 

in 10 to 15 year contracts. Additional 

financial incentives available for some 

practices. 

NRCS or FSA 

state or local 

office 

Environmental Quality 

Incentives Program 

(EQIP) 

Cropland, range, grazing 

land and other agricultrual practices in accordance with 10- to 15-

land in need of treatment. 

Up to 75% cost-share for conservation 

year contracts. Incentive payments for 

certain management practices. 

NRCS state or 

local office 

Partners for Fish and 

Wildlife Program 

(PFW) 

Most degraded fish and/ 

or wildlife habitat. 

Up to 100% finanical and technical 

assistance to restored widlife habitat 

under a minimum 10-year cooperative 

agreement. 

Local office of 

the U.S. Fish 

and Wildlife 

Service 

Waterways for 

Wildlife 

Private lands. Technical and program development 

assistance to coalesce habitat efforts of 

corporations and private landowners to 

meet common wateshed level goals. 

Wildlife Habitat 

Council 

Wetlands Reserve 

Program 

(WRP) 

Previously degraded 

wetland and adjacent 

upland buffer, with limited 

amount of natural wetland 

and existing or restorable 

riparian areas. 

75% cost-share for wetland restoration 

under 10-year contracts and 30-year 

easements, and 100% cost-share on 

restoration under permanent easements. 

Payments for purchase of 30-year or 

permanent conservation easements. 

NRCS state or 

local office 

Wildlife at Work Corporate lands. Technical assistance on developing 

habitat projects into programs that allow 

companies to involve employees and the 

community. 

Wildlife Habitat 

Council 

Wildlife Habitat 

Incentives Program 

(WHIP) 

High-priority fish and 

wildlife habitats. 

Up to 75% cost-share for conservation 

practices under 5- to 10-year contracts. 

NRCS state or 

local office 

State fish and wildlife agencies as well as private groups may have assistance programs. 

agencies. Readers are also encouraged to contact 

local agents of the USDA Animal and Plant Health 

Inspection Service Wildlife Services and state fish and 

wildlife agencies to address specific problems. 

Landowner Assistance 

A number of programs are available that offer financial 

and technical assistance to improve habitat quality for 

wetland mammals (see above table). With the help of 

such programs and assistance from wildlife and natural 

resource professionals, landowners will be able to 

devise and implement a successful habitat management 

plan for wetland mammals and other wildlife. 

References 

Atwood, E. L. 1950. Life history studies of nutria, or coypu, 

in coastal Louisiana. Journal of Wildlife Management 

14:249-265. 

Bluett, R. 1984. The muskrat. Wisconsin Department of 

Natural Resources, Bureau of Wildlife Management. 

Publ-WM-00984. 

Bolen, E. G., and W. L. Robinson. 1995. Wildlife ecology and 

management, third edition. Prentice Hall, Upper 

Saddle River, New Jersey, USA. 

Bookhout, T. A. 1996. Research and management techniques 

for wildlife and habitats. The Wildlife Society, 

Bethesda, Maryland, USA. 

18
Wetland Mammals 

Bounds, D. L. 2000. Nutria: an invasive species of national 

concern. Wetland Journal 12(3):9-16. 

Bounds, D. L., and G. A. Carowan, Jr. Nutria: a nonnative 

nemesis. Trans. 65th North American Wildlife and 

Natural Resources Conference. 

Burt, W. H. and R. P. Grossenheider. 1980. A field guide to the 

mammals: North America and Mexico. HoughtonMifflin, New York, New York, USA. 

Cowardin, L. M., V. Carter, F. C. Golet, and E. T. LaRoe. 1979. 

Classification of wetlands and deepwater habitats 

of the United States. U.S. Fish and Wildlife Service. 

FWS/OBS-79/31. 

Evans, J. 1970. About nutria and their control. U.S. Fish and 

Wildlife Service, Resource Publication 86. 

Godin, A. J. 1977. Wild mammals of New England. Johns 

Hopkins University, Baltimore, Maryland, USA. 

Hammer, D. A. 1992. Creating freshwater wetlands. Louis 

Publishers, Chelsea, Minnesota, USA. 

Helms, J. A., ed. 1998. The dictionary of forestry. The Society of American Foresters, Bethesda, Maryland, 

USA. 

Hobson, S. S., J. S. Barclay, and S. H. Broderick. 1993. 

Enhancing wildlife habitats: a practical guide for 

forest landowners. Northeast Regional Agricultural 

Engineering Service. NRAES-64. Ithaca, New York, 

USA. 

Hyngstrom, S. E., R. M. Timm, and G. E. Larson., eds. 1994. 

Prevention and control of wildlife damage— 1994. 

University of Nebraska Cooperative Extension, 

USDA Animal and Plant Health Inspection Service, 

and Great Plains Agricultural Council, USA. 

Illinois Wildlife. Mink. Illinois Department of Conservation. 

20M-7-81. 

Kinler, N. W., G. Linscombe, and P. R. Ramsey. 1987. Nutria. 

Pages 327-342 in Wild Furbearer Management and 

Conservation in North America. M. Novak, J. A. 

Baker, M. E. Obbard, and B. Mallock, eds. 

LeBlanc, D. 1994. Nutria. Animal and Plant Health Inspection 

Service. Animal Damage Control, Port Allen, 

Louisiana, B71-B80. 

Merritt, J. F. 1987. Guide to mammals of Pennsylvania. 

University of Pittsburgh, Pittsburgh, Pennsylvania, 

USA. 

Milne, R. C. and T. L. Quay. 1966. The foods and breeding 

habits of the nutria on Hatteras Island, North 

Carolina. Proceedings of the Annual Conference of 

Southeastern Association Fish and Game 

Commissions 20:112-113. 

Mitsch, W. J. and J. G. Gosselink. 1986. Wetlands. Van 

Nostrand, Reinhold, New York, USA. 

Naiman, R. J., J. M. Melillo, and J. E. Hobbie. 1986. Ecosystem 

alteration of boreal forest streams by beaver (Castor 

canadensis). Oecologia 62:150-55. 

National Audubon Society. 1993. Saving wetlands: a citizen’s 

guide for action in the mid-Atlantic region. MidAtlantic Regional Office, Camp Hill, Pennsylvania, 

USA. 

Niering, W. A. 1992. Wetlands. Alfred A. Knopf, New York, 

New York, USA. 

Payne, N. F. 1992. Techniques for wildlife habitat management 

of wetlands. McGraw-Hill, New York, New York, 

USA. 

Willner, G. R., J. A. Chapman, and D. Pursley. 1979. 

Reproduction, physiological responses, food habits, 

and abundance of nutria on Maryland marshes. 

Wildlife Monographs No. 65. 

Wood, G. W. and L. A. Woodward. 1992. The Clemson 

beaver pond leveler. Proceedings Annual 

Conference Southeast Association Fish and 

Wildlife Agencies 46:179-187. 

19
Wetland Mammals 

Wildlife Habitat Management Institute 

100 Webster Circle, Suite 3 

Madison, Mississippi 39110 

(601) 607-3131 

In cooperation with partners, the mission of 

the Wildlife Habitat Management Institute is 

to develop and disseminate scientifically based 

technical materials that will assist NRCS field 

staffs and others to promote conservation stewardship of fish and wildlife, and deliver sound 

habitat management principles and practices 

to America’s land users. 

www.whmi.nrcs.usda.gov 

Wildlife Habitat Council 

1010 Wayne Avenue, Suite 920 

Silver Spring, Maryland 20910 

(301) 588-8994 

The mission of the Wildlife Habitat Council is 

to increase the amount of quality wildlife habitat on corporate, private, and public land. 

engages corporations, public agencies, and private, non-profit organizations on a voluntary 

basis as one team for the recovery, development, 

and preservation of wildlife habitat worldwide. 

www.wildlifehc.org 

WHC 

Primary author: Holly L. May, Wildlife Habitat Council 

The United States Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the 

basis of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, and marital or familial 

status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for 

communication of program information (Braille, large print, audiotape, etc.) should contact the USDA’s TARGET Center 

at (202) 720-2600 (voice and TDD). 

To file a complaint of discrimination write USDA, Director, Office of Civil Rights, Room 326-W, Whitten Building, 14th and 

Independence Avenue, SW, Washington, DC 20250-9410 or call (202) 720-5964 (voice or TDD). USDA is an equal 

opportunity provider and employer. 

20