Index of Species Information
WILDLIFE SPECIES: Ondatra zibethicus
Introductory
WILDLIFE SPECIES: Ondatra zibethicus
AUTHORSHIP AND CITATION :
Snyder, S. A. 1993. Ondatra zibethicus. In: Fire Effects Information System, [Online].
U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station,
Fire Sciences Laboratory (Producer). Available:
www.fs.usda.gov/database/feis/animals/mammal/onzi/all.html [].
ABBREVIATION :
ONZI
COMMON NAMES :
common muskrat
water rat
rat
TAXONOMY :
The currently accepted scientific name for common muskrat is Ondatra zibethicus
[7]. There are 16 subspecies that differ in population status,
distribution, habits, and habitat [14]:
1. O. zibethicus ssp. zibethicus
2. O. zibethicus ssp. albus
3. O. zibethicus ssp. aquilonius
4. O. zibethicus ssp. bernardi
5. O. zibethicus ssp. cinnamominus
6. O. zibethicus ssp. goldmani
7. O. zibethicus ssp. macrodon
8. O. zibethicus ssp. mergens
9. O. zibethicus ssp. obscurus
10. O. zibethicus ssp. occipitalis
11. O. zibethicus ssp. osoyoosensis
12. O. zibethicus ssp. pallidus
13. O. zibethicus ssp. ripensis
14. O. zibethicus ssp. rivalicius
15. O. zibethicus ssp. spatulatus
16. O. zibethicus ssp. zalophus
ORDER :
Rodentia
CLASS :
Mammal
FEDERAL LEGAL STATUS :
None
OTHER STATUS :
Information on state- and province-level protection status of animals in the
United States and Canada is available at NatureServe, although recent changes
in status may not be included.
WILDLIFE DISTRIBUTION AND OCCURRENCE
WILDLIFE SPECIES: Ondatra zibethicus
GENERAL DISTRIBUTION :
Common muskrats are distributed across North America from northern Alaska and
Canada south to parts of the Gulf Coast and northern portions of Mexico
[1]. They are found in northern and central California, parts of
southern Arizona, northern Utah and Nevada, most of New Mexico, the
Texas Panhandle, and eastern Texas, and a small part of western Texas
and the Louisiana coast. Common muskrats are not found in Florida or coastal
Georgia and South Carolina [14]. Ranges for each subspecies are given
below [14]:
1. O. z. zibethicus - eastern U.S. and southeastern Canada
2. O. z. albus - Manitoba and adjacent central Canada
3. O. z. aquilonius - Labrador and adjacent Ungava and Quebec
4. O. z. bernardi - Colorado River areas of southeastern California,
southern Nevada, and western Arizona and Mexico
5. O. z. cinnamominus - Great Plains
6. O. z. goldmani - southwestern Utah, northwestern Arizona, and
southeastern Nevada
7. O. z. macrodon - mid-Atlantic Coast
8. O. z. mergens - northern Nevada and parts of adjacent states
9. O. z. obscurus - Newfoundland
10. O. z. occipitalis - coastal Oregon and Washington
11. O. z. osoyoosensis - Rocky Mountains and southwestern Canada
12. O. z. pallidus - southcentral Arizona and west-central New Mexico
13. O. z. ripensis - southwestern Texas and southeastern New Mexico
14. O. z. rivalicius - southern Louisiana, Mississippi coast,
western Alabama, and eastern Texas
15. O. z. spatulatus - northwestern North America
16. O. z. zalophus - southern Alaska
ECOSYSTEMS :
FRES17 Elm-ash-cottonwood
FRES18 Maple-beech-birch
FRES28 Western hardwoods
FRES36 Mountain grasslands
FRES37 Mountain meadows
FRES38 Plains grasslands
FRES39 Prairie
FRES40 Desert grasslands
FRES41 Wet grasslands
FRES42 Annual grasslands
FRES44 Alpine
STATES :
| AL |
AK |
AZ |
AR |
CA |
CO |
CT |
DE |
GA |
ID |
| IL |
IN |
IA |
KS |
KY |
LA |
ME |
MD |
MA |
MI |
| MN |
MS |
MO |
MT |
NE |
NV |
NH |
NJ |
NM |
NY |
| NC |
ND |
OH |
OK |
OR |
PA |
RI |
SC |
SD |
TN |
| TX |
UT |
VT |
VA |
WA |
WV |
WI |
WY |
DC |
| AB |
BC |
MB |
NB |
NF |
NT |
NS |
ON |
PE |
PQ |
| SK |
YK |
|
|
MEXICO |
BLM PHYSIOGRAPHIC REGIONS :
1 Northern Pacific Border
2 Cascade Mountains
3 Southern Pacific Border
4 Sierra Mountains
5 Columbia Plateau
6 Upper Basin and Range
7 Lower Basin and Range
8 Northern Rocky Mountains
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountain Piedmont
14 Great Plains
15 Black Hills Uplift
16 Upper Missouri Basin and Broken Lands
KUCHLER PLANT ASSOCIATIONS :
K049 Tule marshes
K073 Northern cordgrass prairie
K074 Bluestem prairie
K075 Nebraska Sandhills prairie
K077 Bluestem - sacahuista prairie
K078 Southern cordgrass prairie
K090 Live oak - sea oats
K101 Elm - ash forest
K114 Pocosin
SAF COVER TYPES :
16 Aspen
63 Cottonwood
108 Red maple
217 Aspen
235 Cottonwood - willow
SRM (RANGELAND) COVER TYPES :
NO-ENTRY
PLANT COMMUNITIES :
Common muskrats inhabit wetland plant communities comprised of cattail (Typha
spp.), bulrush (Scirpus spp.), sedge (Carex spp.), reed (Phragmites
spp.), cordgrass (Spartina spp.), saltgrass (Distichlis spicata), and
black rush (Juncus roemerianus) [1,14].
BIOLOGICAL DATA AND HABITAT REQUIREMENTS
WILDLIFE SPECIES: Ondatra zibethicus
TIMING OF MAJOR LIFE HISTORY EVENTS :
Breed - March through October, peaking from March through June
Age of Maturity - from 6 to 8 weeks or 1 year
Gestation - 28 to 30 days
Litter - 4 to 7 kits north of 37 degrees north latitude, with 3 or fewer
litters per year; 3 to 4 kits south of 37 degrees north
latitude, with 3 or more litters per year; young are altricial
Weaning - 4 weeks
Life Span - up to 4 years in the wild [14]
PREFERRED HABITAT :
Common muskrats prefer sloughs, marshes, oxbow lakes, streams, levees, dikes,
and small lakes and ponds [1]. Along the Gulf Coast, they prefer
brackish marshes over freshwater marshes. Common muskrats build lodges in or
near water (within 3.3 feet [1 m]), using marsh vegetation.
Alternatively, they construct elaborate bank burrows that may be up to
45 feet (15 m) long [1,14]. Entrances to both lodges and burrows are
usually under water, and both are multichambered. During periods of low
water, common muskrats dig canals from lodges and burrows to deeper water
areas. They also build feeding platforms to get out of the water to
eat, or feeding huts for protection from the elements and predators
[14]. Common muskrats will usually stay within 45 feet (15 m) of their lodges
while foraging, although they can range out to 550 feet (183 m). Habitat
suitability index models have been developed for common muskrats inhabiting
inland freshwater and Atlantic or Gulf coast estuarine areas [1].
COVER REQUIREMENTS :
Common muskrat populations tend to be higher in areas with dense aquatic,
emergent vegetation that is surrounded by terrestrial herbaceous
vegetation. Forested riverbanks usually do not support common muskrat
populations. High quality habitat is characterized by 50 percent or
more of an area having dense emergent species, although if habitats
become "choked" with vegetation, common muskrat numbers will be low. Ideal
ratios for vegetation to water are 75:25 to 80:20 [1].
Water levels and velocities affect common muskrat habitat [14]. Typically, if
levels are too low, food availability will also be low. This is most
pronounced in winter when low water levels allow freezing of the
substrate, killing food and cover species [1,14]. Stream gradients and
velocities were studied in Massachusetts to determine habitat selection
by common muskrats. Streams with gradients more than 47.5 feet per mile (9.0
m/km) and flows less than 4 cubic feet per second (cfs) (0.1 m3/sec) did
not support common muskrats. However, common muskrats were found in streams with
gradients less than 32.2 feet per mile (6.1 m/km) and flows greater than
4 cfs. River habitats with flows greater than 1,000 cfs (28 m3/sec)
typically experience scouring and water level fluctuations too great to
support common muskrat populations [1].
In some cases more than a 2-foot (0.6 m) rise in lake levels forces
common muskrats out of burrows and lodges, although some fluctuation is
necessary for regeneration of emergent vegetation [1]. Lake and pond
depths of between 18 inches and 4 feet (0.46-1.2 m) may be ideal.
Islands and coves can usually provide additional shoreline and more
vegetation for food and cover than bodies of water without these
features. Recommended water depths in Gulf coastal marshes are 0.8 to
11.8 inches (2-30 cm) year-round. Levels should not fall more than 3.1
inches (8 cm) below the substrate so that Olney bulrush (Scirpus
olneyi), a highly preferred food for common muskrats, can regenerate [1].
Common muskrats need emergent vegetation and a firm substrate for building
lodges [1]. They rarely use submergent vegetation. Optimum sites for
bank burrows are on slopes of 30 degrees or more, with a minimum height
of 1.6 feet (0.5 m). Maximum breeding density for common muskrats is 5 pairs
per hectare [14].
FOOD HABITS :
Common muskrats eat the basal parts, rhizomes, and leaves of aquatic emergent
vegetation. Although they consume mostly plant material, they eat some
fish, crustaceans, dead birds, and frogs [14]. In Gulf coastal marshes,
Olney bulrush is an important food [16]. Plant food species vary with
common muskrat distribution, but some of the major foods are cattail, bulrush,
sedge, arrowhead (Sagittaria spp.), waterlily (Nymphaea spp.), wild rice
(Zizania aquatica), sweetflag (Acorus calamus), pondweed (Potamogeton
spp.), pickerelweed (Pontederia cordata), spikerush (Eleocharis spp.),
smartweed (Polygonum spp.), clover (Trifolium spp.), bluestem
(Andropogon spp.), rice (Oryza spp.), panicgrass (Panicum spp.),
paspalum (Paspalum spp.), burreed (Sparganium spp.), millet (Echinochloa
spp.), willow (Salix spp.), poplar (Populus spp.), and some crops. They
also consume acorns and maple (Acer spp.) samaras [1,14,16].
PREDATORS :
Common muskrat predators include humans, mink (Mustella vison), raccoon
(Procyon lotor), bobcat (Felix rufus), house cat (F. domesticus),
domestic dog (Canis familiaris), coyote (C. latrans), red fox (Vulpes
vulpes), barn owl (Tyto alba), barred owl (Strix varia), great horned
owl (Bubo virginianus), northern harrier (Circus cyaneus), bald eagle
(Haliaeetus leucocephalus), eastern cottonmouth (Agkistrodon
piscivorus), alligator (Alligator mississippiensis), snapping turtle
(Chelydra serpentina), bullfrog (Rana catesbeiana), garfish (Lepisosteus
spp.), bowfin (Amia calva), and largemouth bass (Micropterus salmoides)
[14]. Common muskrats will kill the young of other common muskrats when populations
are too dense.
MANAGEMENT CONSIDERATIONS :
A variety of animals use common muskrat lodges including snakes, turtles,
toads, Canada geese (Branta canadensis), and black terns (Childonias
niger) [14].
Common muskrats can reduce cattail enough to allow purple loosestrife (Lythrum
salicaria), an undesirable weed, to replace cattail and degrade marsh
quality [15].
Management of water levels can have a strong impact on common muskrat habitat
because of fluctuation influences on certain food species [14].
Drawdowns can have a negative impact on common muskrat populations [17]. Low
water levels may encourage undesirable species to take over. Prolonged
flooding can destroy food plants [14]. Water levels in Louisiana
coastal marshes strongly influence the distribution of Olney bulrush
[13]. Recommended water levels for these areas are between 0.5 to 2.0
inches (1.3-5.0 cm), and never less than 2.0 to 3.1 inches (5-8 cm)
below the substrate [13,14]. Recommended water levels for Maine are
between 6 and 20 inches (15-51 cm) [14]. For detailed information on
how water levels affect cattail refer to Weller [19]. For more detailed
information on general affect of water level refer to Perry [14].
Common muskrat populations tend to follow a roughly six- to 14-year cycle,
where low numbers leading to good food supplies are followed by a
population boom and a subsequent decline in common muskrat numbers [4,14]. In
Gulf coastal marshes these booms cause "eat-outs", which are areas of
extensive overharvest of Olney bulrush by common muskrats. This usually occurs
in pure Olney bulrush stands, and can have a detrimental impact on
stands. Bulrush must establish within 5 months after an "eat-out"
occurs or it will die out [16]. Regeneration can occur through
sprouting from rhizome fragments in the substrate. Prolonged flooding
can delay regeneration in "eat-out" areas. For more in-depth discussion
on management of Olney bulrush refer to Sipple [16].
In some areas mosquito control projects can destroy marshes, as can
dredging, diking, and urban sprawl [15].
FIRE EFFECTS AND USE
WILDLIFE SPECIES: Ondatra zibethicus
DIRECT FIRE EFFECTS ON ANIMALS :
Common muskrats can be killed by fire either through direct mortality or
complete kill of food and cover [12]. The latter was observed in
Louisiana peat marshes with shallow clay pans during drought years.
When detritus accumulates and fire ignites during dry spells, the fire
can burn intensely and move rapidly, killing common muskrat populations [12].
HABITAT RELATED FIRE EFFECTS :
Periodic marsh burning is usually necessary to remove dead vegetation,
cycle nutrients, and increase vigor of desirable plant species.
Conversely, if detritus is allowed to accumulate, fires can become
severe enough to destroy desirable species [12].
Mid-July burning of marshes "choked" with common reed (Phragmites
communis) in Manitoba resulted in an increase of common muskrat populations
[18]. Reed did not reach preburn densities until 4 years later.
Olney bulrush increases in cover following burning [10,16]. If this
species is not periodically burned, it can be replaced by needlerush
(Eleocharis acicularis), sawgrass (Cladium jamaicense), and pineland
threeawn (Aristida stricta), which are less desirable food and cover
species for common muskrats. Seventy-five to 100 percent of needlerush,
sawgrass, and pineland threeawn can be removed by fire [14]. Burning
saltmeadow cordgrass (Spartina patens) will remove it, allowing for
succession by Olney bulrush. Cordgrass outcompetes Olney bulrush in the
absence of fire [16]. Burning cordgrass and saltgrass (Distichlis
spicata) during "normal" water levels may not be as effective as burning
when water levels are lower in the fall, or until late spring following
a flooding treatment with water levels between 10 and 15 inches
(25.4-38.1 cm) [16].
FIRE USE :
Fire can be used to set back succession of marshes (common muskrats thrive in
early seral vegetation stages), prevent the accumulation of detritus,
control undesirable species, and promote good growing conditions for
Olney bulrush [8,14]. When burning Olney bulrush stands, it is best to
leave 0 to 2 inches (5 cm) of standing water, and burn between
mid-October and the first of January [12,16]. Olney bulrush grows
throughout the winter, and burning just before or during this time will
give it a good advantage over other species. Burning dates will vary
for different areas, and burning may be necessary every year or two
except during times of drought [16]. When burning to eliminate
needlerush, do so in late February or early March and when it is dry
enough so that needlerush is damaged [14]. Switchgrass (Panicum
virgatum) and Olney bulrush should establish by the second or third
postfire year. Burning Atlantic coastal marshes is recommended in late
winter to ensure adequate winter cover for common muskrats [14].
FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find Fire Regimes".
REFERENCES
WILDLIFE SPECIES: Ondatra zibethicus
REFERENCES :
1. Allen, Arthur W.; Hoffman, Robert D. 1984. Habitat suitability index
models: muskrat. FWS/OBS-82/10.46. Washington, DC: U.S. Department of
the Interior, Fish and Wildlife Service. 27 p. [21637]
2. Bernard, Stephen R.; Brown, Kenneth F. 1977. Distribution of mammals,
reptiles, and amphibians by BLM physiographic regions and A.W. Kuchler's
associations for the eleven western states. Tech. Note 301. Denver, CO:
U.S. Department of the Interior, Bureau of Land Management. 169 p.
[434]
3. Chabreck, Robert H. 1968. The relation of cattle and cattle grazing to
marsh wildlife and plants in Louisiana. Proceedings, Annual Conference
Southeastern Association of Game and Fish Commissioners. 22: 55-58.
[14503]
4. Errington, Paul L.; Siglin, Roger J.; Clark, Robert C. 1963. The decline
of a muskrat population. Journal of Wildlife Management. 27(1): 1-8.
[17542]
5. Eyre, F. H., ed. 1980. Forest cover types of the United States and
Canada. Washington, DC: Society of American Foresters. 148 p. [905]
6. Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; [and others].
1977. Vegetation and environmental features of forest and range
ecosystems. Agric. Handb. 475. Washington, DC: U.S. Department of
Agriculture, Forest Service. 68 p. [998]
7. Honacki, James H.; Kinman, Kenneth E.; Koeppl, James W., eds. 1982.
Mammal species of the world. Lawrence, KA: Allen Press Inc. 694 p.
[13703]
8. Kelleyhouse, David G. 1979. Fire/wildlife relationships in Alaska. In:
Hoefs, M.; Russell, D., eds. Wildlife and wildfire: Proceedings of
workshop; 1979 November 27-28; Whitehorse, YT. Whitehorse, YT: Yukon
Wildlife Branch: 1-36. [14071]
9. Kuchler, A. W. 1964. United States [Potential natural vegetation of the
conterminous United States]. Special Publication No. 36. New York:
American Geographical Society. 1:3,168,000; colored. [3455]
10. Lay, Daniel W.; O'Neil, Ted. 1942. Muskrats on the Texas coast. Journal
of Wildlife Management. 6(4): 301-311. [14561]
11. Messier, Francois; Virgl, John A. 1992. Differential use of bank burrows
and lodges by muskrats, Ondatra zibethicus, in a northern marsh
environment. Canadian Journal of Zoology. 70(6): 1180-1184. [18437]
12. O'Neil, Ted. 1949. The muskrat in the Louisiana coastal marshes. New
Orleans, LA: Louisiana Department of Wildlife and Fisheries, Fish and
Game Division, Federal Aid Section. 152 p. [18182]
13. Palmisano, Angelo W., Jr.; Newsom, John D. 1968. Ecological factors
affecting occurrence of Scirpus olneyi and Scirpus robustus in the
Louisiana coastal marshes. Proceedings, 21st Annual Conference of
Southeastern Association of Game and Fish Commissions. 21: 161-172.
[15303]
14. Perry, H. Randolph, Jr. 1982. Muskrats. In: Chapman, Joseph A.;
Feldhamer, George A., eds. Wild animals of North America: Biology,
management, and economics. Baltimore, MD: The Johns Hopkins University
Press: 282-325. [21638]
15. Rawinski, Thomas J.; Malecki, Richard A. 1984. Ecological relationships
among purple loosestrife, cattail and wildlife at the Montezuma National
Wildlife Refuge. New York Fish and Game Journal. 31(1): 81-87. [18330]
16. Sipple, William S. 1979. A review of the biology, ecology, and
management of Scirpus olneyi. Vol. II: a synthesis of selected
references. Wetland Publication No. 4. Annapolis, MD: Maryland
Department of Natural Resources, Water Resources Administration,
Wetlands Permit Division. 85 p. [20021]
17. Thurber, Joanne M.; Peterson, Rolf O.; Drummer, Thomas D. 1991. The
effect of regulated lake levels on muskrats, Ondatra zibethicus, in
Voyageurs National Park, Minnesota. Canadian Field-Naturalist. 105(1):
34-40. [19873]
18. Ward, P. 1968. Fire in relation to waterfowl habitat of the delta
marshes. In: Proceedings, annual Tall Timbers fire ecology conference;
1968 March 14-15; Tallahassee, FL. No. 8. Tallahassee, FL: Tall Timbers
Research Station: 255-267. [18932]
19. Weller, Milton W. 1975. Studies of cattail in relation to management for
marsh wildlife. Iowa State Journal of Research. 49(4): 383-412. [18158]
20. U.S. Department of the Interior, Fish and Wildlife Service. 1994.
Endangered and threatened wildlife and plants; animal candidate review
for listing as endangered or threatened species; proposed rule. 50 CFR
Part 17. Tuesday, November 15, 1994. Federal Register. 59(219):
58982-59028. [24357]
FEIS Home Page
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