MUSKR

PRODUCTION AND MANAGEMENT

CIRCULAR 18

FISH AND WILDLIFE SERVICE

UNITED STATES DEPARTMENT OF THE INTERIOR

ABSTRACT

The muskrat, largely an inhabitant of low, sub-
marginal lands unsuited to agriculture, is the Nation's
greatest fur resource, and the trapping and handling
of its pelts has developed into an important and valuable
industry.

Despite a high reproductive rate and a remarkable
ability to maintain itself year after year under unfavor-
able conditions, the muskrat is subject to cyclic fluctua-
tions. Periodic reductions in its numbers create con-
siderable apprehension in trappers and others concerned
about its welfare, and result in many requests for
information regarding it.

This circular gives facts on the biology and ecology
of the muskrat, and discusses basic principles of marsh
management that underlie practical muskrat produc-
tion. The material is based on many years of research
by the author and numerous other Federal and State
workers, and on experiences and observations of many
owners of marshes in commercial muskrat production,
muskrat trappers, and fur dealers.

MUSKRAT

PRODUCTION AND MANAGEMENT

BY
HERBERT L. DOZIER

CIRCULAR 18

United States Department of the Interior, Oscar L. Chapman, Secretary
Fish and Wildlife Service, Albert M. Day, Director

UNITED STATES. GOVERNMENT PRINTING OFFICE : 1953

For sale by the Superintendent of Documents, U. S. GoTernment Printing Office
Washington 25, D. C. - Price 20 cents

CONTENTS

Page

Distribution and habits 1

General characteristics 1

Distribution and habitat 2

Home of the muskrat 5

Food of the muskrat 8

Breeding ' 9

Developing the muskrat resource 11

Improving the habitat 11

Estimating muskrat numbers 16

Maintaining a balanced population 21

Harvesting and handling the muskrat crop 24

Traps and trapping equipment 24

Setting the traps 26

Skinning methods 28

Preparing the pelts 29

Marketing the pelts 32

Muskrat meat as food 33

Muskrat farming 34

Raising muskrats in pens - 34

Raising muskrats on natural and fenced areas 35

Farm ponds in relation to muskrats 35

Stocking depleted areas 36

Live-trapping muskrats 36

Handling live muskrats 37

Banding and tagging 38

Identification of sex 39

Shipping live animals 39

Recommendations 40

Note. — Dr. Herbert Lawrence Dozier died December
4, 1951, after the manuscript of "Muskrat Production
and Management" had been submitted for publication.
Final review for publication was completed by Frank G.
Ashbrook.

MUSKRAT PRODUCTION AND
MANAGEMENT

The miiskrat is the most valuable
wild fur animal in the United
States. Increasing use of muskrat
for fur and meat makes it desirable
to assure perpetuation of this ani-
mal as a natural resource. Al-
though injurious in some localities,
it is for the most part an inhabit-
ant of places unsuited for agricul-
ture. Muskrats multiply much
more rapidly than other fur ani-
mals, and because of habitat and
general habits, they are better fitted
than most animals of this class to
maintain their numbers under the
protection given them.

The harvest of muskrats in this
country is six or seven times that
of any other species of fur animal.
In the past 5 or 10 years the take of
muskrat pelts has averaged 18,000,-
000 to 20,000,000 a year, compared
with 3,000,000 opossum, 2,500,000
skunk, 1,500,000 raccoon, 900,000
fox, and 700,000 mink. In some
years top northern muskrat pelts
have brought $4 to $4.55 on the mar-
ket, but they usually average about
$2.50. Southern muskrat prices
run much lower, from 50 cents to
$1.75.

Investigations on the biology of
the muskrat were conducted from
1931 to 1934 by Frank R. Smith, as
a cooperative undertaking by the
Bureau of Biological Survey (sub-
sequently merged into the Fish and

"Wildlife Service), the University
of Maryland, and the Maryland
State Game and Inland Fish Com-
mission, on rtie W. A. Gibbs marsh
near Church Creek, Md., and later
on the Blackwater National Wild-
life Refuge, Cambridge, Md. In
the fall of 1937 these studies were
resumed by the author on a broader
scale, covering research on extensive
inland and coastal marsh areas in
the eastern seaboard and Gulf
States, and continued to 1951.

The author gratefully acknowl-
edges the direction and helpful sug-
gestions of Frank G. Ashbrook; the
valued assistance of Charles E.
Kellogg, William S. Heit, Robert
W. Allen, Leonard M. Llewellyn,
Merle H. Markley, Carl Rossy, and
Solomon R. Willey ; and critical re-
view of parts of the manuscript by
Richard E. Griffith, Francis M.
Uhler, Shaler E. Aldous, and O.
Lloyd Meehean.

DISTRIBUTION AND HABITS

General Characteristics

The muskrat is essentially an
overgrown meadow mouse with fur,
feet, and tail adapted to an aquatic
existence. There are no readily
apparent external differences be-
tween the sexes; adults range from
2 to 5 pounds in weight and reach
an over-all length of about 241/2
inches. The prominent, thick tail.

Figure 1.— Hind foot of the muskrat.
Left, dorsal view ; right, ventral view.

covered with small, scaly areas and
strongly compressed laterally, is
an efficient rudder for swimming.
Long, sharp claws serve admirably
for digging and defense (fig. 1).
The large hind feet, which can be
turned sidewise to reduce resistance
when the muskrat is swimming, are
not webbed but have fringes of
short, stiff hairs that also help in
swimming. The dense pelage is
practically waterproof — the long,
stiff, glistening brown guard hairs
closely interspersed among the
short, soft, and exceedingly dense,
gray underfur.

The muskrat has four protrud-
ing, chisellike incisors to cut its
food, and heavy molars to grind it
( fig. 2 ) . The incisors grow contin-
uously and are gradually replaced
when broken. By closing its lips
tightly around the protruding in-
cisors and blocking the small open-
ing between them with its tongue
(fig. 3), the muskrat can gnaw and
dig loose root material under water.
Short, bristlelike hairs cover the
lips and protect them from sharp
grasses or other rough food plants.

A deep cleft between the upper and
lower lips lets the muskrat open its
mouth wide and carry large mouth-
fuls of food or nest-building mate-
rials.

A pair of highly developed scent,
or musk, glands are located under
the skin in the lower inguinal re-
gion (fig. 4). These yellowish
glands, much larger in the male
than in the female, appear rough-
ened or corrugated. They give off
a pungent, musky odor that is par-
ticularly strong during the breeding
season and accounts for the name
"muskrat." The old Cree name
"musquash" is still used in Canada
and in continental European fur
markets.

Distribution and Habitat

Two distinct species are recog-
nized: the Newfoundland muskrat
{Ondatra obscurus) and the com-

FiGURE 2.— Lower and upper parts of
muskrat skulls, showing incisors and
grooved molars.

Figure 3. — Mouth of the muskrat.
Above, subadult with mouth closed ;
below, adult with mouth open revealing
the cleft, hairy lips and tongue.

mon eastern muskrat {Ondatra
zihethicus), of which there are 14
subspecies.

The fur of the muskrat varies in
color from a dark, rich brown to a

fulvous or reddish brown. Color
variants, such as the white or albino
muskrat, have been reported from
the various races but are exceed-
ingly rare. Fur dealers recognize
only a dark, almost black variant of
the common brown muskrat. These
dark pelts represent a distinct
black-and-tan color phase of the
Virginia, or coastal, muskrat
{Ondatra zibethicus Tnacrodon)^
which is found in the tidewater re-
gion of the Atlantic coast from
southern New Jersey to PaJmlico
Sound, N. C. During normal years
they command a much higher price
than the brown pelts, as there is a
ready export market for the limited
supply.

Of North American origin, the
muskrat occurs throughout the
greater part of the continent from
Bering Strait and the northern tree
limits southward to the Mexican
Border. It is not found along the
coasts of South Carolina or Geor-
gia, in Florida, or in many parts of
California in spite of apparently
suitable habitat. It is absent or
scarce in the Gulf States except in
the coastal strips of Mississippi,

^B^P* -^ "^

f>'i

^•^ -^t:-

Figure 4. — Musk glands of male muskrat.

3

Alabama, Louisiana, and eastern
Texas where large numbers occur.

The muskrat is seldom seen far
from water. Occasional animals
may be seen wandering in a field or
along the highway but this is usu-
ally the result of drought, flood, the
scarcity of food, or the breeding
season. Its habitat falls in three
natural divisions: (1) Small
streams, river banks, creeks, ponds,
lakes, and canals; (2) swamps; and
(3) marshes.

In the first habitat group — rivers,
lakes, ponds — no one favored food
is abundant. The muskrats subsist
on a variety of succulent aquatics,
underground roots, and upland
plants obtained in their overland
forages. They live along water-
courses with their nest dens located
at the end of bank burrows. Such
fresh-water conditions are charac-
teristic of the group of North
Central States — Michigan, Illinois,
Ohio, Indiana, Iowa, and Wiscon-
sin— that forms one of our largest
muskrat-producing areas.

The swamp habitat includes low,
timbered country, with dense
stands, fluctuating water levels, and
intermittent pools of still water —
the sluggish streams bordered by
thickets and dense stands of large
trees. Conditions in general are
poor for muskrat production, in this
type of habitat; and although the
muskrat is protected from many of
its enemies and escapes ready ob-
servation, it must depend for its
food supply mainly on the marsh
plants and limited stands of cattail
that occur along the edges of the
swamp and in the more open areas.

The most important type of

muskrat habitat falls under the
general term "marsh." Here are
included the extensive fresh and
brackish marshes of the coastal re-
gions and the great inland fresh-
water areas of cattail and river and
round-stemmed bulrushes. It is in
the vast coastal marshlands that the
muskrat is found in greatest num-
ber (fig. 5).

Some coastal marshes are diked,
or enclosed with an earthen bank,
with sluice gates at various points
to permit some control of water
depths (fig. 6) . These marshes are
called banked meadows to distin-
guish them from wild tidal marsh.
When employed in muskrat produc-
tion, such a marsh is kept wet
enough to ensure a good growth of j
food plants. Properly flooded, I
diked meadows are said to produce
more muskrats to the acre than any
other type of marsh. This type of
marsh management is most common
along the New Jersey coast.

Tidal marshes are penetrated by
a system of meandering rivers,
small ditches, creeks, "guts," and
numerous ponds. Most of the
marshes along the coast and border-
ing the larger bays, like the Dela-
ware and Chesapeake Bays, are
largely saline. Their vegetation
consists principally of big cord-
grass {Spa/rtina cyiiosuroides) ,
saltmarsh cordgrass {S. altemi-
■flora)^ saltmeadow grass {S. pat-
ens), saltgrass {Distichlis spicata),
and dense stands of needlerush
{Juncus ro erne ri anus). These
plants have little value as muskrat
food.

Inland from the coast and bays,
where tidal waters and the fresh-

^tUT'^'dtair' ^^-^fcC^r^^'

Figure 5. — The number of houses on this "three-square" marsh in Maryland indicates
a heavy population of muskrats.

water runoff meet, slightly saline
conditions develop. Extensive
three-square {Scirpios olneyi, /S.
americanus) marshes interspersed
with stands of cattail ( Typha spp. ) ,
reed or "roseau" cane {Phragmites
communis)^ and patches of big
cordgrass {Spm^tina cynosuroides)
result. Soils of these marshes are
waterlogged or partially sub-
merged, and living conditions for
the muskrats approach the ideal.
The three essentials required to sus-
tain a maximum muskrat popula-
tion are met : (1) An abundance of
suitable aquatic vegetation for food
and protective cover; (2) sufficient
fresh or slightly saline water for
swimming and proper sanitation;
and (3) the most suitable type of
bottom (peaty humus) in which to
dig canals, underground tunnels,
and runways.

Home of the Muskrat

Muskrats need little protection
during the summer and live in the

open marsh in almost any kind of
makeshift shelter. In the fall when
high tides arrive and cold weather
approaches, they become very ac-
tive, adding to their old houses or
pushing up new ones, and digging
runways and canals.

For survival, muskrats depend
largely on concealment. They
spend much of their lives in their
underground tunnels and burrows,
in their nests and feeding shelters,
in swimming, and in digging and
gnawing at the roots of various

Figure 6. — ^Type of sluice gate commonly
used in "diked-meadow" muskrat
marshes in New Jersey.

Figure 7. — Clump of three-square bul-
rush (Scirpiis olneyi). The fibrous
roots are used extensively in house
construction, and the larger, runner
roots are highly prized by the muskrat
for food.

aquatic or swamp plants. Conse-
quently, their presence in an area is
detected by the evidences of their
activity rather than by observations
of the animals themselves.

Nesting or dwelling houses

The muskrat nesting or dwelling
house, also known as a bed or lodge,
is constructed of the fibrous-root
masses and stems of aquatic plants
growing in the area (fig. 7). It
may rest on the bottom of a shallow
pond or on clumps of marsh grasses.
Built by heaping up freshly cut
material, the dome-shaped nesting
house is distinguished by its large
size, elliptical shape, and peaked or
lopsided const ruction ( fig. 8 ) . The
heights of the houses vary from 16
inches to 4 feet, depending on the
supply of vegetation available, se-

verity of the season, and fluctua-
tions in the water levels. The walls
are from 4 inches to a foot thick,
and openings in them are closed
with mud. This keeps the nest
warm in winter and cool in summer.
When an inhabited house is opened
during the fall or winter, a dry
well-lined nest, or chamber, is found
above the water line with several
"runs" down to plunge holes under
the water.

Feeding shelters

The feeding shelter, or hut, is a
place to which the muskrat can
bring food and eat it protected
from its enemies and from the
weather. Several feeding shelters
may be constructed near the dwell-
ing house at convenient distances,
their number and sturdiness de-
pending on the need.

The feeding shelter is distin-
guished from the dwelling house by
its smaller size, roughly circular
outline, low height of 12 to 16 inches
above water level, and more round-
ed and uniform shape (fig. 9).
When it is opened a small central
feeding platform containing plant

Figure 8. — Typical muskrat house in
Maryland "three-square" marsh in
winter, showing mud runway and fresh
patching.

6

FiGfRE 9. — Occupied muskrat house in "blue flag" cattail ( Typha glauca ) (right) with
smaller feeding shelter marsh in central New York.

remains is usually found just above
the water line (fig. 10). Several
runs lead from it beneath the water.
On the Atlantic coastal marshes
where climatic conditions are less
severe than on northern marshes,
the tightly constructed hut is re-
placed by a flimsy feeding shelter.
Open feeding platforms are used
during the summer, and in more
southern areas throughout the year.

Push-ups or breathers

Not to be confused with the feed-
ing shelter which it resembles super-
ficially, the push-up or breather is
generally found in the frozen
marshes of the northern States and
Canada, and is confined to the
deeper channels, rivers' edges, and
lakes. As soon as ice forms in the
fall, the muskrats start building
push-ups by cutting holes in the ice
about 4 or 5 inches across and push-
ing fibrous roots, waterweeds
and other submergent vegetation
through the openings. This is in
marked contrast to the bulkier stems
and leaves of cattails and other

emergents they use in constructing
feeding stations. A 12- to 18-inch
mass is formed on the ice above the
hole, and a cavity is made on the
inside which the muskrats use as
a shelter and breather. During se-
vere weather they also are used as
feeding stations. With the arrival
of spring and thawing of the ice,
the structure collapses.

Bank dens

Muskrats living along the edge
of woods, stream banks, and drain-

FiouRE 10. — Feeding shelter with side cut
away to expose feeding platform with
remnants of winter shoots of "blue
flag" cattail left by muskrat.

210220 O— 53-

FiGTJBE 11. — Entrances to "pipe lead" tunnels at three levels in bank of tidal river,
Maryland — at low^ tide.

age ditches often do not build
houses, but burrow into the stream
banks. Entrances to these burrows
are usually under water most of the
year. A burrow may have several
entrances at varying depths built at
different times to meet changing
water levels (fig. 11). The tunnels
lead back into a main burrow and
then upward into one or more large
nesting chambers which are well
above water level. The larger bur-
rows may have well-hidden surface
openings that are kept loosely
plugged and undoubtedly function
as air vents.

The muskrat's habit of burrow-
ing into dams, levees, canal banks,
and other embankments to build its
home often leads to serious dam-
age— to the structure itself and to
adjacent agricultural lands by flood-
ing them or by draining waters from
irrigated crops. Levees and dikes
in rice fields of the South, in west-
ern irrigation projects, and in fish
hatcheries are especially vulnerable
to the burrowing activities of the
muskrat. Muskrats often under-
mine shelled corduroy roads in the

marsh country, making travel haz-
ardous at times and road mainte-
nance a constant expense.

Control of destructive muskrats
must be in accordance with local
regulations; the State conservation
department should be consulted by
the landowner before he attempts to
remove the offending animals. Re-
moval usually is by trapping, shoot-
ing, or digging the muskrats out of
their burrows.

Food of the muskrat

The diet of the muskrat varies
with the season and the plants avail-
able. Chiefly herbivorous, in some
localities the muskrats may feed to
a limited extent on crayfish, crabs,
mussels, snails, minnows, and slug-
gish fish. These items are thought,
however, to constitute a relatively
minor and seasonal phase of their
diet.

The muskrat's food is varied in
summer, consisting of leaves and
roots of many aquatics, such as the
cattails, wildrice, arrowhead or
duck potato, waterlily, marshaster
{Boltonia asteroides), pond weeds
{Potamogeton spp.), waterweeds

8

Figure 12. — Dense stands of saltinarsh
bulrush, or coco (Scirpus robustns),
i'avorite food of niuskrats and water-
fowl.

{Anacharis spp.), and occasionally
smartweed. The inland fresh-
water areas, in which "coopers" or
"blue-flag" cattail {Typha glauca)^
broadleaved or common cattail {T.
lafi folia), and burreed (Sparga-
nium spp.) are major food plants,
produce the largest muskrats and
the best pelts. In some northeast-
ern sections the European flower-
ing rush {Butomits umheUatim) is
being used in increasing amounts.
Throughout the north central and
northwestern United States the
hardstem bulrush {Scirpus acutus)
and the river bulrush {S. fluviati-
lis) are outstandingly important
food plants. In the great muskrat-
producing marshes of the Atlantic
coast and of the Gulf of Mexico, the
three-squares {Scirpvs olneyi, S.
am-ericanus) and saltmarsh bulrush
{Scirpus rohustus) (fig. 12) are
staple foods, and wherever the West
Indian cattail {Typha domingen-
sis) occurs it is highly relished.

In the winter, when plants are
dormant (fig. 13) and ponds and
marshes are frozen over, the musk-
rat lives mainly on the underground

parts of plants. Unlike many other
rodents, it does not store great
quantities of food for this critical
period and must depend on its abil-
ity to dive and, while submerged,
dig and gnaw loose pieces of the
roots and lower stems of aquatic
plants.

Muskrats eat a wide variety of
cultivated plants when available.
They are especially fond of carrots,
corn, raw peanuts, clover, alfalfa,
soybeans, and wind-fallen apples,
and will travel considerable dis-
tances from their dens, located
along streams and ditches adjacent
to farm properties, to obtain them.

Breeding

In the spring, patching of the old
houses heralds the beginning of the
breeding season and of preparations
for the young. Although muskrats
usually pair off and share the home-
making duties, they are not strictly
monogamous. Trapping breaks up
many families and members of both
sexes readily accept new mates. At
times the males are highly polyga-
mous; this results in considerable
fighting when one is searching for

Figure 13. — Clump of cattail cut from
beneath the ice. The muskrat is es-
pecially fond of the green, dormant
winter buds.

9

Figure 14.— Muskrat litter a few hours
old.

a mate and invades another's terri-
tory. This is particularly in evi-
dence in spring during the active
mating period when muskrats fre-
quently show bites and slash marks.
Mating takes place during the
latter part of March. The gesta-
tion period is rather short, 28 or 29
days. The first, or early-spring,
litters are usually born between
April 27 and May 5— the period
that is most productive in the total
number of young born and that has
the highest rate of survival of
young. In northern areas, two lit-
ters, and occasionally a third, are
produced a year. In Maryland,
three litters a season are common,
the third being born in August or
September; on rare occasions a
fourth litter may be produced very
late in the year.

Spring and fall litters are usually
born in small nests that are hol-
lowed out inside the house, or bed,
and lined with fresh shoots of very
fine grass. In northern regions the
nests are lined with finely shredded
pieces of cattail. In summer, birth
of the young may take place in more
open situations or on rafts made of

cattails, rushes, or grass ; in brush
piles; or in flimsily constructed
nests thrown up just above the reach
of high tide.

The size of the muskrat litter has
been recorded as ranging from 1 to
13 young but evidently it varies
with the race concerned. The com-
mon eastern muskrat {Ondatra z.
zibetUcus) averages 6 young
throughout most of its range; the
Virginia or coastal muskrat {0. z.
macrodon) averages 4.4 young ; and
the Louisiana muskrat {O.z. rivali-
cius) averages but 3.85, seemingly
compensating for this low number
by producing as many as four or
five litters a year.

Muskrats weigh less than an
ounce at birth and are blind, almost
naked, and helpless (fig. 14). Dur-
ing the lactation period the mam-
mae, or teats, of the muskrat are
retractile and the tips are some-
what recurved. When a nursing
mother is disturbed she plunges un-
der water, the young clinging to
her; if some are torn loose the
mother usually manages to retrieve
them.

The young muskrats develop rap-
idly and their eyes open in 14 to 16
days after birth (fig. 15). Known
as mice, they often begin to nibble
on green, succulent vegetation be-

FiGURE 15.— At l.'i days young muskrats
have well-developed fur, and the eyes
are just beginning to open.

10

fore they are weaned at about 4
weeks of age. By that time the in-
cisors are well developed and can
inflict pain. Growth is remarkably
rapid but depends on the abundance
and quality of their food, on water
and temperature conditions, and on
racial characteristics (fig. 16). In
Maryland, a total length of nearly
18 inches and a weight of about I14
pounds may be reached at 7 months.
Size of the muskrat at maturity
may differ considerably between re-
gions and between races. By the
end of the trapping season, young
of the first spring litter of the Vir-
ginia muskrat may not weigh more
than 2 pounds 3 ounces, whereas in
central New York those of the com-
mon eastern muskrat may reach
slightly more than 3 pounds.

In spite of the belief of many
trappers to the contrary, young
muskrats do not mature sufficiently
to breed during the year of their
birth. By the next spring breeding
season, however, young of the early
spring litters have reached matur-
ity. In Louisiana, where young
have been found in every month of
the year, it is possible that kits born
early in January may mature and
breed by the end of December ; but
confirmatory data on this are lack-
ing.

DEVELOPING THE MUSKRAT
RESOURCE

Large areas, formerly considered
worthless except as waterfowl
marshes are today being used to
produce muskrats. With the in-
crease in the value of muskrat fur,
many areas totally unsuited for
farming, even when drained, are

Figure 16. — A 2-months-old Maryland
muskrat.

yielding a greater income than ad-
joining, cultivated fields. A better
understanding of the application of
modern management practices to
such properties has helped to stabi-
lize muskrat production at a high
level.

Good muskrat habitat is usually
good waterfowl marsh. Both for
waterfowl and for muskrats, tight
or solid marshes are undesirable.
The effect of muskrats on a water-
fowl marsh is important. In their
normal activities muskrats create
ponds and keep channels open, but
allowed to increase uncontrolled
they deplete the vegetation and ruin
the habitat both for waterfowl and
for themselves.

Improving the Habitat
Controlling water levels

Maintenance of proper water
levels is very important as muskrat
populations are affected more by
rapid changes in water levels than
by changes in the type of marsh
vegetation. Extreme fluctuation is
damaging both to muskrats and to
their food plants. A freshet, or
sudden rise of water in the spring,
often results in heavy mortality of
the very young. Again, lowered
water levels in late spring followed
by intense and prolonged summer
drought and high temperatures can
stop breeding and lower the rate of
survival of the young.

11

• Quite often it is possible to divert
sufficient water from larger streams
and rivers to maintain small lakes
and ponds. Extensive fresh-water
areas have been created on some
marshes by constructing dikes (fig.
17). Some elaborate concrete
water-control structures and spill-
ways may be necessary, but often
earthen and rock dams will suffice —
the excess water simply flows over
the top.

Water-control structures should
be designed so that water levels can
be raised or lowered as the need
arises. A temporary "draw-down"
of the water to expose the soil dur-
ing the first half of the growing
season is one of the most effective
methods of obtaining germination
of the seeds of cattail and bulrushes
and the establishment of the seed-
lings. The exposed soil should be
kept moist and not permitted to dry
out. Ponds are a conspicuous fea-
ture of coastal marshes and valuable
in varying degrees to waterfowl,
fur animals, and other wildlife. A
good marsh is one having a ratio of
about 80 percent vegetation to 20
percent open water.

On a tidewater marsh, the differ-
ence of a few inches in water levels
has a marked influence on the plants
and animals found there. Their
natural distribution is governed by
their ability to withstand varying
degrees of intermittent and pro-
longed submergence and by their
tolerance to different concentrations
of salts or chlorides.

Brackish marshes extend along
the Atlantic coast and the Gulf of
Mexico — the result of the mixing of
the salt waters from the sea and the

• ■^e^raHp^lRw^PgSBP''**''

Figure 17. — Using a dragline to construct
a dike with an impervious core of
marl.

fresh waters coming down to the
coast from the interior. Prolonged
droughts and high temperatures in-
crease salinity of the water in these
marshes. Often not much can be
done to correct such a situation, but
all sources of fresh water such as
runoff from woods, fields, and
drainage ditches should be used.
Unfavorable water conditions on a
marsh can frequently be improved
by diverting water from a nearby
stream, or by a small amount of
judicious diking, coupled with the
use of deep wells, either free-flow-
ing or pumped (fig. 18). In some
instances dynamite-blasting of a
series of small ponds and connect-
ing ditches across a high, "tight" i
marsh encourages its use by musk- I
rats. Care must be taken to avoid
lowering ground-water levels that
control the gi^owth and distribution
of essential food plants. Upper
reservoirs or pools may be con-
structed to impound water that can
be used to stabilize water levels in
the lower ponds and ma:rshes.

Level ditching is practiced exten-
sively in the Gulf Coast marshes,
not only to help control fluctuations
in water levels but also to lessen
difficulty of foot travel by trappers.

12

:#i#n ..^»^^^"-'^"^' '"" '^""^

^ ^,-^.— ■..■.•:5*.!,*«e^

Figure 18. — This heavy concentration of houses on part of a Virginia tidal marsh,
supplied by a windmill-pumped well during drought, illustrates the influence of fresh
water on the distribution of the muskrat population.

Marsh walking becomes extremely
difficult in thick growths of saw-
grass, bullwhip, and reed. By
opening up a series of connecting
ditches, pirogues or narrow, flat-
bottomed mudboats can be used, and
traps set along the levees or ditch
banks used by muskrats, raccoons,
minks, and otters for feeding and
travel lanes. The system of small
ditches also carries off excessive
storm and flood waters, but retains
water during periods of drought.
Care should be taken in ditch con-
struction to prevent any general
lowering of the' water table on

which the desired type of plant
formation is so dependent.

It is wasted effort to attempt to
drain soft, floating types of marsh,
but "eat-outs," which are spots in
the marsh denuded of vegetation by
muskrats (fig. 19), should be tem-
porarily drained. Otherwise they
quickly deteriorate into stagnating
muck flats or expanses of open wa-
ter. Immediate drainage to remove
stagnating water allows sunlight
to reach the bottom and create bet-
ter conditions for seed germination
and revegetation. Neglected, these
spots may take years to come back.

*0'f%

Figure 19. — Beginning of an "eat-out" on a Maryland marsh. Intense trapping should
be started long before this stage is reached.

13

Drainage can be effected by cutting
drainage ditches some 30 inches
wide and deep to lead the water
from the denuded spots. The use
of blind or closed ditches prevents
the intrusion of sea water in coastal
marshes. After the areas have been
satisfactorily drained, the ditch
ends should be closed to raise the
water levels again, or the marsh
may be seriously damaged. Ex-
treme care must be exercised in
ditching a marsh so as not to alter
the water relations and thereby
favor invasion of the marsh by un-
desirable vegetation.

Increasing the food supply

On marshes having water-control
structures it is often possible to in-
crease the supply of desirable musk-
rat food plants by manipulating
water levels. Many undesirable
plant competitors can be controlled
by raising the water level a few feet
and maintaining it for several
months. The areas opened up by
killing off noxious plants should
then be planted, preferably in the
spring, with such food plants as the
cattails {Typhu glauca, T. lati-
folia)^ the three-square bulrushes
{Scirpus olneyi^ S. americarms) ,
saltmarsh bulrush {S. rohiostws),
and the hardstem bulrush {Scirpus
acutit^ ) . Pieces of roots with buds
attached are transplanted into the
muck at the edges of the impounded
areas. The two exotics, water-
hyacinth {Eichhornia crassipes)
and alligatorweed {Altemanthera
philoxeroides) have become estab-
lished in recent years in the coastal
marshes of Louisiana ; and despite
numerous attempts to control them

Figure 20. — Beneficial effect of burning
"three-square" bulrush is apparent in
this Maryland marsh, control-burned
in February ; on May 22 the burned-
over areas were in full bloom, while
new growth in the small, unburned
part adjacent to the shell road (left)
was just emerging.

by various mechanical means or by
spraying with weed killers, they are
fast clogging the extensive network
of canals and bayous. In certain
localities these weeds have increased
to such an extent that they almost
dominate the native plants. While
water-hyacinth is scarcely touched
by the muskrat, alligatorweed at
times is used to a considerable ex-
tent, and in the Mississippi area
often forms as much as 15 percent
of the muskrat's diet.

Fire is an imjjortant factor in the
ecology of any marsh, and con-
trolled burning is an accepted tool
in marsh management. It must be
recognized, however, that a certain
amount of cover is essential to pro-
tect the muskrat from its enemies.
To the trapper in the old days burn- fl
ing merely meant easier trapping '
and more three-square. Marsh
burning is beneficial in that it de-
stroys the "rough" and prevents
elevation of the marsh through peat
accumulation (fig. 20).

14

Figure 21. — Several muskrar runs leading to the dwelling house were exposed when
this "three-square" marsh in Louisiana was burned.

Marshes on the xVtlantic coast are
burned about the middle or the
latter part of February. To burn
in early fall would mean little cover
for the muskrats until late spring.
In the Gulf Coast marshes three-
square is burned between October
10 and January 1 when the water is
only a few inches deep (fig. 21).
This helps maintain a supply of
three-square bulrush, a favored
food of the muskrats.

The beneficial effects of marsh
burning appear to outw^eigh any un-
favorable ones. Burning opera-
tions indirectly control insects that
attack many of the favorite food
plants of the muskrat, such as the
widely distributed and very injuri-
ous lepidopterous stem borer of cat-
tail {Arazama obUqua) and several
leaf miners on three-square bulrush
that often prevent normal seed set-
ting over large areas. Productive

muskrat marsh should never be
burned during an abnormally dry
spell, as root burns occur then, seri-
ously altering the marsh structure
and killing desirable vegetation.
Deep burns can be used effectively
in breaking up dense stands of the
less desirable Spartina patens.
During very dry periods, marsh
fires result in the death of many
rabbits and raccoons, and occasion-
ally muskrats, minks, and otters.
If there is some water on the marsh
at the time of the fire the loss is gen-
erally slight. Fortunately, inhabi-
tated muskrat houses are rather
moist and chinkei with mud, and do
not burn readily ; the only damage
to them is a slight blackening and
scorching of their tops.

Generally speaking, cattle and
muskrats do not go well together.
Cattle trample the muskrat houses
and runw^ays and frequently dam-

210220 0—53-

15

Figure 22. — Marsh raccoons prey exten-
sively on young muskrats.

age the trap sets. Electric fences
may be employed to contrql graz-
ing. The extent to which grazing
can be effective in opening up dense
stands in marshes is questionable,
owing to the soft muck bottom char-
acteristic of such formations. At
times cattle can be used to advan-
tage in bulrush and giant cutgrass
{Zizaniopsis miliacea) , but this re-
quires capacity grazing plus tempo-
rary drainage to be fully effective
in deep marshes. Grazing heavy
sawgrass ( Cladium jamaicense )
marsh, even in periods of moderate
drought, is exceedingly difficult.
In addition, the sawgrass is unpal-
atable except for the very tender
new growth that follows a burn.

Controlling enemies of the
muskrat

Foxes, raccoons, and minks may
be economic liabilities in muskrat
management. Where they are
found the cause of serious loss, ex-
cess numbers of them should be re-
moved in accordance with State
laws, preferably by trapping dur-
ing the open season. At this time
their pelts are prime and bring the
best prices. Some economic re-
turns can thus be realized from the
animals removed ; at the same time

16

undue pressure on the muskrat is
reduced.

Wherever the mink is abundant
it is rated the most serious enemy
of the muskrat. In the marshes of
the Atlantic coast the red fox and
the marsh-dwelling raccoon exact a
heavy toll, especially of the young
( fig. 22) . The raccoon is one of the
worst predators in the Gulf Coast
marshes, and it is also a bad trap
robber. Over its range the coyote
is reported to prey on the muskrat.

Marsh-owners and trappers in
some sections report that the wild
razor-backed hog at times has been
such a serious drain on muskrat
numbers — tearing open the houses
and eating the young — that special
hog hunts have been organized.
The black snake, water moccasin,
alligator, garfish, and snapping
turtle account for many muskrats
and on more northern marsh areas
the pike and muskellunge are occa-
sional predators.

Birds of prey to some extent feed
on the muskrat. Chief of these are
the red-tailed hawk, the marsh
hawk, and the great horned owl;
but the principal damage is to the
trapped animals. The bald eagle
has been charged with feeding on
muskrats. Examination of an
eagle's nest by one Maryland marsh-
owner disclosed more than 40 musk-
rat traps in the nest, proving at
least that this bird is a trap robber,
like the "buzzard" and the crow.

Estimating Muskrat Numbers

Fluctuations in muskrat
populations

In years of normal rainfall and
temperature, muskrats may become

Figure 23. — Upper: Maryland marsh in March 1938, at the peak of the nmskrat-
population cycle as indicated by density of houses and badly eaten condition of the
marsh. Lower : Same marsh at low of the muskrat cycle, April 1944.

so plentiful that they deplete their
food supply. During these years of
abundance their numbers build
gradually to a peak, but not simul-
taneously over the country, and
then abruptly decline (fig. 23).
Such major fluctuations cannot be
attributed to trapping variation.
Canadian fur records accumulated
over a period of many years show
that fluctuations in muskrat popu-

lations tend to move in more or less
definite 10-year cycles. More recent
but incomplete records from various
parts of the ITnited States confimi
the fact that distinct periods of
abundance and scarcity exist, but
indicate that the cycle in some in-
stances is longer than 10 years.
These cycles are not fully under-
stood at present, but undoubtedly
the two major factors responsible

17

Figure 24. — A Louisiana muskrat heavily
infested with stomach worms.

for such radical decline in the popu-
lation are disease and prolonged in-
tense drought.

Drought brings about catastroph-
ic changes for the muskrat. Thou-
sands of small ponds, lakes, and
pools dry up, and food becomes
scarce. As water levels sink, the
muskrats are forced from their
homes and many die while search-
ing for more favorable conditions.
The supply of fresh water is re-
duced, and in the coastal marshes
salinity increases as the runoff from
the watershed fails. The normally
fresh or slightly saline water is re-
placed by undesirable salt water
from the sea.

Disease, too, takes its toll, often
coupled with poor water conditions.
Despite its reputation as a generally
healthy animal, the muskrat is sub-
ject to numerous maladies, includ-
ing lobar pneumonia, septicemia,
enteritis, streptococcus infections,
tumors, coccidiosis, tularemia, leu-
kemia, lumpy jaw, and a skin ail-
ment of fungous origin. In addi-
tion to these diseases, the species is
host to some 65 parasites, mostly
nematodes (fig. 24), trematodes,
and cestodes.

"Lousy" muskrats are often re-
ported by trappers, but examina-

tion usually reveals the presence of
small mites instead of lice. Heavy
infestations during the breeding
season may result in the loss of
many new-born litters. Muskrats
with inflamed eyes are frequently
encountered, and this condition also
is caused by mites. If such animals
are held for a few days in a pen or
box, supplied with fresh water, and
dusted with an insecticide, such as
sulfur or rotenone, the condition
often clears.

Coccidiosis is common in penned
muskrats. This disease may be rec-
ognized by the reddened and in-
flamed appearance of the intestines
and the presence of oocysts. The
oocysts may be seen in the diseased
tissue with the aid of a microscope.
Coccidiosis thrives in the pollution
that occurs on partly dried ponds
and still-water marshes during
droughts and it can greatly reduce
a muskrat population in a few
weeks. Where water levels can be
controlled and fresh water is avail-
able, it is never a serious factor.

In some years epizootics, or out-
breaks of disease over widespread
areas, appear usually just before the
opening of the trapping season.
Thousands of muskrats die in a few
weeks, and trappers working over
such marsh areas may find numbers
of dead animals with no sign of in-
jury but in emaciated condition.
The majority of sick muskrats,
however, die unobserved in their
underground runs. Old burrows
and houses may serve as focal
points, or centers of infection, and
some marshes remain death traps
with recurrent epizootics over a pe-
riod of several years. Some of

18

these muskrat 'Svipe-outs" have
been attributed to the paratyphoid
organism, Salmmiella typhim/u-
riimu by various workers, but it is
now generally agreed that an uni-
dentified virus is responsible for
most of the loss. The hemorrhaged
character of the lungs and intes-
tines is the best indicator of the dis-
ease. The Peyer's patches of the
small intestines are often conspicu-
ously enlarged, and look like a mass
of frog's eggs through the intestinal
wall. Numerous gray necrotic
spots are usually present on the
liver.

Estimating muskrat populations

As the density of a muskrat pop-
ulation is constantly changing, an
accurate estimate of the numbers
present on a marsh is required each
year for intelligent management.
Practical estimates can be made
fairly easily and accurately in late
fall by counting the conspicuous,
haycock-shaped houses, or beds,
scattered over the marsh.

The house count is recognized as
an excellent management tool for
estimating anually the number of
muskrats on an area, determining
population trends, assigning areas
to trappers and fixing their limits,
and regulating trapping quotas.
State conservation officials are in-
terested primarily in drastic i-educ-
tions or increases in the general
population as a basis for shortening
or lengthening the legal trapping
season. The marsh manager needs
such information to make trapper
assignments and set trapping quo-
tas. These counts also offer an ex-

cellent opportunity to make obser-
vations on the types of vegetation
and cover, changes in the abundance
of nmskrat foods, and predation
and disease.

House counts caai be made from
the ground or from an airplane and
are most accurate after a killing
frost has leveled the rank marsh
vegetation. On the Atlantic coast
the muskrats begin pushing up
their houses in early September,
with the arrival of the high tides.
Construction of new houses and
patching of the old ones continue
through the first week in November.
This is the ideal time for a count.
At this time, theoretically, the
maximum muskrat population, in-
cluding the young-of-the-year, is
present, and provides the truest
basis for estimating populations
and establishing trapping quotas.

Transects and counts from road-
sides have been used by some tech-
nicians to estimate muskrat popu-
lations. Although acceptable on
some areas, these methods generally
are unsatisfactory.

Unquestionably, the most accu-
rate population estimate can be
made from the ground by a "strip"
count, if trained personnel is avail-
able to cover the area adequately.
The various units must be well
delimited by natural boundaries or
by markers. Reference to a field
map of the area to be covered is
useful as knowledge of the natural
features is necessary for an effective
survey. Weather and tides must be
considered when choosing the time
to make a count, but for compara-
tive purposes the units should be

19

counted at approximately the same
time each year and in much the
same order.

In making a strip count the crew-
is lined up at the most logical start-
ing point on the area to be cen-
sused. The men are placed about
50 feet apart — a convenient width
of strip for each counter. The ob-
jective is to cover as wide a strip as
possible, but the type and density
of the vegetation determine this to
a large extent, as all muskrat houses
and feeding stations must be clearly
seen. The two men on the outside
lines are responsible for guiding
the crew. Each counter moves
down a strip and counts from him-
self to the man on his left or right,
as predetermined, using a hand
tally machine. The counters on the
outside are responsible for marking
the outer limits of the area by heap-
ing muskrat-house material into
small towers on the larger houses;
these temporary mounds are readily
discernible from a considerable
distance.

The strip-count method must be
modified in areas that are badly
eaten out by the muskrats, or that
are broken up by numerous ponds,
creeks, or guts. If the topography
is such that the strip-count method
cannot be used, it may be advisable
to assign a unit or a marsh to a sin-
gle counter. Bank dens occurring
along drainage ditches or streams
in a strip being censused are in-
cluded, but care must be taken to
count only the main entrances to
the dens. They are usually the
larger entrances and have more
signs of being used.

20

An aerial census provides a
quicker and more-economical meth-
od of counting houses than does the
ground count. Its accuracy can
also be checked against photo-
graphs made during the flight (fig.
25). An aerial observer often
covers in a few hours an area that
would require a three-man ground
crew several days. The strip count
is generally employed in an aerial
census — the pilot moving back and
forth across the area being cen-
sused, in much the same manner as
in the ground strip count. Bound-
ary markers must be clearly visible
from the air. On badly eaten areas
the muskrat houses stand out
clearly, but dense vegetation pre-
sents difficulties. With good visi-
bility the larger houses can be seen
from 800- to 1,000-foot elevations
over a %-mile radius. After a
snowfall, or when a count of indi-
vidual trapping units is desired,
lower-level observations at 200 feet
or less become necessary. Counts

Figure 25. — Against the dark water,
muskrat houses on this North Carolina
coastal marsh appear as numerous
white spots from the air. Count of the
houses serves as a practical basis for
determining the population.

can be made from the air in more-
northern areas even when the marsh
is covered with snow. In wind-
swept areas the snow is quickly
blown from the tops of the houses,
making them stand out. Under
more-moderate conditions, the
warmth generated by the muskrats
in an occupied house is sufficient to
melt most of the snow from the
crown of the house, while the feed-
ing huts remain covered. In
marshes that are burned early in
the fall, as in the Gulf States, the
straw-colored houses stand out
clearly against the blackened,
charred vegetation.

Determination of the muskrat
population on the basis of the house
count requires some knowledge of
the number of muskrats usually
found in an occupied house. The
last litter of the season usually re-
mains with the parents through the
first winter and until the spring
mating season begins. Observa-
tions of the writer indicate that the
litter size varies with the race. The
number of animals in a dwelling
house will depend, therefore, on the
average litter size of the race con-
cerned and the survival rate at the
time the house count is made.

The arbitrary count of five musk-
rats to a large house or bank den is
frequently used as a conversion
figure in estimating muskrat popu-
lations. This may be too low a
figure for good years. When
known, the average litter size of the
race concerned is preferred to con-
vert the number of inhabited
houses, as determined in the house
count, into population estimates.

Maintaining a Balanced
Population

Controlling muskrat numbers by
trapping

An important principle of suc-
cessful muskrat management under
natural conditions is that the an-
nual crop be harvested at the right
time both for maximum economic
returns and for sustained yield.
Muskrat populations cannot be car-
ried over from year to year to build
a huge crop for a single trapping
season. High population densities
are a danger signal and removal of
the surplus animals is the key to
successful fur-animal management.
The majority of State and National
wildlife refuges are managed pri-
marily for waterfowl. The prob-
lem is to keep the muskrat in the
status of an asset rather than a lia-
bility, and trapping excess numbers
of this fur animal is necessary.

The productivity, or carrying
capacity, of a marsh 'depends
largely on the type and quantity of
its vegetation and on the amount of
its brood stock. There is also a
direct correlation between the size
and weight of a muskrat and the
quality and abundance of food
available to it. Under Atlantic-
coast tidewater conditions, trap-
ping should be undertaken w^hen the
population density reaches that of
one house to the acre. A density of
2.5 dwelling houses an acre calls for
immediate, intensive trapping to
prevent serious eat-outs. Allow^ed
to increase uncontrolled, muskrats
will deplete the vegetation and
cause the marsh to revert to open
w^ater and mud flats. The animals
are then forced to migrate to sur-

21

vive. On a good marsh it is gen-
erally possible to remove two-thirds
of the muskrats each trapping sea-
son and still reserve sufficient brood
stock for a sustained annual crop,
as muskrats are so prolific that it is
extremely difficult to overtrap them
during the comparatively short
legal season.

The average number of muskrats
trapped on an acre of the best type
of Maryland marsh over a long
period is 4 or 5, and catches of up
to 10 animals to the acre under ex-
cellent trapping conditions have
been reported. A Cameron Parish
(Louisiana) marsh of 3,000 acres
yielded 68,656 muskrats in 1946-47,
or approximately 23 muskrats to
the acre. The marsh had to carry
30 to 35 animals to the acre to make
a catch of this size possible, and
represented an advanced case of
overpopulation. By the end of the
trapping season the better parts of
the marsh had been eaten out.

The "yield per house" has been
found to be a much better indicator
of trapping efficiency than the
"yield per acre." An average of 2
muskrats to an occupied house is
considered good trapping in view of
the difficulties encountered in trap-
ping, fluctuations in weather and
tides, and movements of the ani-
mals. As a rule, an average of 2.5
muskrats per house can be removed
without jeopardizing the breeding
stock for the next season.

Trapping success is dependent on
several factors : to a very great ex-
tent on prevailing weather condi-
tions that at times seriously hamper
the trapper, as well as the experi-
ence, energy, and reliability of the

trapper. Each trapper should be
assigned sufficient territory to as-
sure him a reasonable and equitable
return, but the unit should be small
enough to permit thorough trap-
ping. In general, 150 acres of good
marsh is about all one man can trap
efficiently in a normal season.
Some years it may be necessary to
double this acreage and also resort
to spot trapping to attract the
trappers.

Composition of the population

From a management standpoint
it is highly desirable that the man-
ager of a muskrat marsh, should
know the proportions of mice, kits,
subadults, and adults removed dur-
ing the trapping season. It is from
this information that he can deter-
mine the successfulness of the pre-
vious breeding season and the rate
of survival of the young. An ab-
normally high catch of adults indi-
cates little breeding during the pre-
vious season or a poor rate of sur-
vival of the young-of-the-year. An
abnormally low proportion of
adults indicates very close trapping
or overt rapping in either the pre-
vious or the current year. Size is
generally used to separate subadults
from the adults, but alone it is not
entirely reliable — there is consider-
able overlapping of weights and
measurements in the two groups.
Young individuals from better hab-
itats are often larger and heavier
than older animals from poorer
areas. A combination of characters
such as weight, length, thickness of
skin, pelage or fur quality, and
toughness in skinning, should be
considered in determining age

22

Figure 26. — Female reproductive tract of the Virginia muskrat (Ondatra s. macrodon) .
Left: Early-spring-litter subadult showing small, glistening, thin-walled uterine
horns. Center : First-breeding-season adult showing pigmented placental scars of
two litters, of three young and five young, as indicated by the relative size of con-
gested areas. Right : Older adult almost ready for spring mating ; horns slightly
swollen, cream-colored, and with only an indication of pigmentation remaining.

groups. Kits have thin, papery
pelts of a soft, downy quality.
Tough, thick pelts unquestionably
denote adults.

Internal examination of the re-
productive tract will dispel any
doubt about the age group to which
a muskrat belongs. The condition
of their reproductive tracts distin-
guish the productive females from
the nonproductive (fig. 26). In
muskrats that have recently pro-
duced young the mesenteries ad-
joining the horns of the uterus con-
tain small areas of minute, con-
gested blood vessels. Pigmented
dark spots that occur on the uterine
forks, or horns, represent placental
scars, or sites of embryonic attach-
ment. These scars remain distin-
guishable from the birth of the lit-
ter until the latter part of the fol-
lowing February when they start
to disappear. By early March

these scars usually have entirely
cleared and the uterine horns have
become cream-colored and slightly
swollen in direct contrast with those
of the subadult female, which are
small, glistening, and thin-walled.
Since placental scars do not per-
sist into the new breeding season,
the productivity of the females can
be determined only during the late
fall and winter. Early in the trap-
ping season the scars are distinct
and can be counted, and the average
number of kits to a litter deter-
mined. In many cases, the actual
number of litters produced that
breeding season can be checked by
the comparative size and the dis-
tinctness of the pigmented spots.
The spots vary for each of the lit-
ters, the smallest and the faintest
denoting the oldest litter. Such a
count can be a relatively accurate
index for races that produce but

23

two litters a season and few young
to the litter. In races that have
large litters and produce three or
more litters a season, a count of the
scars becomes complicated and less
reliable. Productivity of the fe-
males and the ratio of young-of-
the-year to adults, as determined
during trapping operations, indi-
cate the trend in muskrat produc-
tion on any particular marsh.

HARVESTING AND HAN-
DLING THE MUSKRAT
CROP

The extreme versatility of musk-
rat fur permits its use as a substi-
tute for some of the more costly
furs, and results in a continuous de-
mand for it. There are more than
half a million licensed professional
trappers in the United States, and
countless farm families find both
sport and economic gain in trap-
ping during the open season.

In the era of open lands and free
trapping it was a question who
could get there first, and most pub-
lic lands were practically stripped
of their fur animals. Trapping to-
day is under State control and regu-
lated by law. The legal season for
trapping muskrats often runs con-
currently with that for other fur-
bearing animals, such as the mink
and otter. Some northern States,
because of heavy snow and ice, have
a short season in the fall followed
by another in the spring. In sev-
eral States the period January 1 to
March 15 has been found desirable.
Except in an unusually hard win-
ter, a season of this length provides
some good trapping weather and

the desired thinning of the fur-
animal population results.

Muskrat pelts do not begin to
prime until late November or early
December, and generally are at
their best the latter part of Febru-
ary. Fall trapping yields many
small, flat, and unprime skins.
Harvesting in early winter de-
creases winter kill from freeze-outs,
food shortage, and disease. If the
season is extended very late in the
spring the trapper can deplete the
breeding stock with bank, floating-
log or other open-water sets. By
this time, breeding has started and
many pregnant females are taken
and the pelts are less desirable as
they are becoming "springy."

Some States set a limit of 250
traps to the trapper and require
that a metal tag, with the name of
the trapper, be attached to each
trap. Registration of trap lines,
which is required in the far North,
reduces poaching and is an incen-
tive to the trapper to leave sufficient
brood stock for another year.

Traps and Trapping Equipment

Each trapper should be provided
with the best types of traps to pro-
mote the greatest trapping effi-
ciency. Steel traps Nos. 1 and l^/^
are generally used to trap muskrats.
There are several types of steel trap
and the popularity of each varies
with the individual trapper and the
part of the country he comes from.
The old Gibbs two-trigger trap is
still widely used in Louisiana. A
trap with strong spring action often
breaks the legbone, so that the
animal tears loose or wrings off,
leaving a foot in the trap. "Stop-

24

Figure 27. — This New York trapper,
standing beside a muskrat house on a
badly eaten cattail-burreed marsh, is
well equipped to trap on the frozen
marsh.

loss" traps are usually equipped
with a delayed-action overguard.
When sprung, they hold the trapped
animal in such a tight position that
it cannot gnaw or wring loose and
escape. Older-type traps that a
trapper may have on hand can be
utilized along river banks and in
deeper water where the muskrat is
quickly drowned by its struggles.

Traplines should be visited each
day for the best results. When
there is ice or heavy snow, warm
clothing, rubber boots or waders, a
long-sleeved glove, and an ax are
necessary equipment (fig. 27). Ice
grippers on the soles of the rubber
boots help prevent falls on slippery
ice. A long box rigged on sled run-

FiGURE 29. — Snowshoes, pack basket, ax,
and snow toboggan are required equip-
ment for trapping in heavy snow.

ners helps in carrying traps and
poles into the frozen marsh and in
bringing a large catch out (fig. 28).
Toboggans and snow-float sleds
serve a similar purpose in deep
snows and drifts (fig. 29). The
spring thaw with its soft ice neces-
sitates the use of lightweight boats
equipped with steel runners (fig.
30) . In Louisiana, the narrow flat-

FiGURE 28. — A box on runners is often
used to bring in the catch from frozen
marshes.

F'iGURE 30. — Thaw-outs do not stop the
trapper equipped with a lightweight
boat such as this one, of white cedar
with metal runners to protect the wood
and make the boat easier to handle on
ice.

25

Figure 31.— The Louisiana trapper uses a
pirogue to carry him through the marsh
and to bring in his catch ; he may also
use it for soaliing and washing his traps
before he stores them.

bottomed boat, or pirogue, is a ne-
cessity when trappers are following
the network of small ditches and
trails through the marsh (fig. 31).
Where practicable, mudboats pow-
ered by inboard motors are used.

Traps rust badly, and if not prop-
erly treated and stored they last but
a few seasons. At the close of the
trapping season many trappers
soak their traps in water for a few
days, dry them, and remove the ac-
cumulated rust with a stiff brush.
They then dip the traps for a few
seconds in hot water to each gallon
of which a quart of old crankcase
oil has been added. Lastly, they
dry the traps and store them in
burlap sacks or in barrels.

Setting the Traps

The manner of setting traps de-
pends on existing conditions and
varies with the section of country in

which the trapper is operating. An
experienced trapper looks for cer-
tain signs of muskrat activity when
deciding where to place his traps.
These signs may take the form of
narrow channels, or runs, through
the marsh between nesting sites and
nearby feeding grounds, air bubbles
under the ice (fig. 32), bank bur-
rows, plant cuttings, roiled or
muddy water in leads, tracks (fig.
33), defecating posts (fig. 34),
plunge holes, and houses and feed-
ing huts. Newly constructed houses
and old ones with fresh repairs
usually indicate occupancy.

Knowledge of muskrat behavior
helps the seasoned trapper. In gen-
eral, muskrats are nocturnal and
most active from dusk to about 11
p. m. and in early morning. Their
diurnal activity seems to vary with
race and geographic location.
Tidewater muskrats feed most ac-
tively during floodtide and hole up
in their nests at ebbtide. Muskrats
of the Virginia and Louisiana races
are extremely wary and are seen
during sunlight hours only occa-
sionally ; those of the common east-
ern and Great Plains races show

Figure 32.— Air bubbles made by musk-
rats under the ice are a sign of musk-
rat activity and guide the trapper in
setting his traps.

26

..^ .

\:

jM.

Figure 33.— Muskrat tracks in fresh mud.
The lines are made by the animals
dragging their tails at times.

considerable diurnal activity and
traps set for thern may be visited
several times a day with good
results.

Traps may be placed in the mud
of the trail or runway slightly un-
der water. As the muskrat runs or
swims over the trap its foot usually
strikes the pan and releases the
spring and trap jaws. The trap is
secured by a chain to a slender pole
so that the animal cannot escape

Figure 34. — Muskrat defecating jiost.
Their number in a marsh is an indi-
cator of the size of the muskrat pop-
ulation.

l3Ii#

^

' /

Figure 35. — Floating-log trap set. Musk-
rats often use such logs as feeding
platforms.

with it. When traps are set in the
deeper leads or in open water, the
struggling animals are pulled under
and quickly drowned. Dirt mounds
scattered along the edges of some
of the main channels are attractive
to muskrats for denning. Sets
placed in approaches to these dens
and along the leads into dike banks
give excellent results.

A floating log (fig. 35), or one
extending out into the water from
the bank, is often used to support
a few traps as the muskrats fre-
quently use such locations as feed-
ing platforms or as highways.
Shallow notches, wide enough to
hold several traps, are cut into the
log, the trap chains fastened to the
sides by staples, and the traps cov-
ered lightly with leaves, grass, or
waterweed. Floating-board sets
are good substitutes for logs — the
traps being placed just beneath the
water on attached, slanting boards.

In many States trapping inside a
muskrat house, or setting a trap
Avithin 6 feet of it is prohibited by
law. A distinction should be made,
however, between the feeding hut,

27

«L%';?M^f^.lMMA^WI!

Figure 36. — A favorite muskrat trap set
in many northern marshes is under the
ice at the entrance of the lead into the
feeding shelter.

or shelter, and the larger dwelling
house. Under frozen conditions
one of the most productive sets is
made by cutting through the ice
into a lead to a feeding hut and
setting the trap so that the pan is
tripped as the muskrat enters the
hut (fig. 36).

Sloping-board and shelf sets are
used in some areas for trapping un-
der ice. The length of the board
depends on the depth of the water.
In the sloping-board set, the trap is
held in place by a small cleat and
an arrangement of two or three
nails about halfway up the board.
A piece of bait, such as carrot, ap-
ple, or parsnip, is nailed to the
board 2 or 3 inches above the trap.
The board is then shoved through a
hole in the ice at about a 45° slant
until its lower end rests in the mud.

The shelf set is made by setting
the trap on a right-angled shelf
nailed to an upright board and
shoved downward through the ice
until it sticks firmly in the mud and

both trap and bait are under water.
Another under-the-ice set can be
made by placing a trap in the crotch
of a willow or dogwood sapling.
When the spring break-up arrives,
these methods are abandoned for
the floating-board or other open-,
water sets.

Skinning Methods

It is advisable to skin muskrats
as soon as possible after catching
them. Skinning is more easily done
while some body heat remains, and
both skins and carcasses keep better
if handled at once. Removal of the
pelt requires careful cutting and
pulling; and with a little practice
it can be done quickly.

There are several methods of
holding a muskrat while skinning
it. Some trappers hold the animal
in their laps; others place it on a
board resting between their legs.
Another method in common use is
to start the skinning operation and
then suspend the muskrat by its tail
with a looped cord (fig. 37). In
Delaware, a short, lengthwise slit is
usually cut in the tail which is
forced over a nail to suspend the
muskrat. An old swivel-type No. 1
jump trap, nailed to a board, makes
an excellent device for holding the
animal firmly during skinning —
the tail gripped in the steel jaws
(fig. 38) . A rather unique but sur-
prisingly quick and efficient method
is that of holding the muskrat by
the tail under the heel of the boot
and cutting from an underhand po-
sition (fig. 39).

In skinning, the muskrat should
not be opened along the belly but
should be cased, flesh side out, with

28

1

through and the skin pulled back
peeling easily to the front feet
(fig, 40). Strong pressure by the
thumb and a quick yank pulls the
skin loose from the front feet, leav-
ing the fur side turned inward.
While this method is fast, it can re-
sult in badly torn pelts. The skin
should be carefully cut around the
ears, eyes, nose, and lips to free it
without tearing.

Preparing the Pelts

After the daily catch has been
skinned, the pelts are usually too
moist to stretch immediately. If a
skin is stretched when wet the dried
fur is thin and straggly in appear-
ance and the pelt is graded down by
the fur buyer. The skins should be
suspended on nails or hooks over-
night by the nose tip, fur side out.
The following morning they are
placed on fur stretchers fur side in,

Figure 37. — The muskrat may be sus-
• pended for skinning by means of a -"H^
looped cord about its tail.

the feet and tail removed. One of
the quicker and better ways of
skinning a muskrat is to pass the
knife around the hind leg just above
the hock in a circular cut, make a
slit from that point up the middle
of the leg to the base of the tail,
around or across it, and down the
other leg to the heel in reverse man-
ner. The body is then pushed

Figure 38. — This New York trapper uses
a swivel-type No. 1 jump trap, nailed
to a board, to hold the muskrat firmly
by its tail while he peels off the skin.

29

Figure 39. — In the underhand method of
removing a muskrat pelt the tail is held
firmly under the boot heel.

and remnants of fat and flesh care-
fully removed (fig. 41). Flesh al-
lowed to adhere to the skin invites
tainting and decay ; excess fat may
make the pelt brittle and subject to
grease burn.

In northern areas, where the
muskrats usually are very fat, it is
often necessary to remove the heavy
layer of fat from the skin with a
dull drawing knife or a specially
devised, steel fleshing tool (fig. 42) .
The skin is placed on a form board
held securely in a bench vise, and
the fat removed with considerable
downward pressure. The extra-
thick, tough skins of these muskrats
permit the use of such a tool. In
Louisiana, the muskrats are smaller
and usually not very fat. The com-
mon practice there is to rinse out
the wet, muddy skins in a bucket
and run them through a clothes
wringer, fur side out (fig. 43). By
this simple process most of the fat
and flesh is squeezed out. The

FiGUKE 40. — TrapiK'rs on the Eastern
Shore of Alaryland prefer the "push
through and pull" method of skinning
muskrats.

Figure 41. — After the pelts have been
cleaned of excess fat and flesh, they
are placed on wire stretchers to dry.

30

Figure 42. — A dull drawing knife or a
specially designed tool, as shown here,
helps remove fat and flesh from the
pelt.

skins are tlien shaken out and sus-
pended by the nose on nails, racks,
or barbed wire to dry before they
are stretched.

The first stretchers were fash-
ioned of thin boards or shingles cut
the desired size and form, with a
few tacks to hold the pelt in place
to dry (fig. 44). Although cheap
and effective, board stretchers have
been almost entirely replaced by
those made of heavy galvanized
steel wire (fig. 45). Several types
of metal stretcher are in use and all
have the advantages of being rust-
proof and almost indestructible.
Compared with wooden stretchers
they give a more uniform stretch
and permit quicker drying, and can
be hung in tiers in a minimum of
space (fig. 46).

Muskrat trappers along the Gulf
Coast still use a very simple type
of heavy-wire stretcher without a
barbed, sliding crossbar. Optimum
stretching of the pelts cannot be
obtained; as a result of this, and
the customary "slashing-across"
method of skinning prevalent in

Figure 43. — A hand wringer is used by
Louisiana trappers to remove blood,
fat, and excess flesh from the skins.

Figure 44. — This view of the attic of
W. A. Gibbs, pioneer trapmaker and
marsh manager, illustrates the old
method of drying muskrat pelts on
wooden stretching boards.

31

Marketing the Pelts

Muskrat skins are universally
case-handled and are dried with the
flesh side out. The fur buyer can
readily check primeness by the ap-
pearance of the skin. The degree
of unprimeness is indicated by the
amount of blue-black streaking or
spotting which occurs in the un-
prime areas where the new hairs
have not yet grown out of their
follicles. Any cuts or tears can be
easily detected.

Three types of muskrat pelts are
recognized in the fur trade: (1)
The brown, or northern; (2) the

Figure 45. — Two popular types of steel-
wire stretchers.

that region, the pelts are easily
distinguished by their short, cut-off
appearance (fig. 47).

Many trappers use attics for dry-
ing pelts. For the best results,
pelts should be dried in a cool, dry,
well-ventilated room with a tem-
perature of 50° to 60° F. Quick
drying with a kerosene stove usually
blackens the pelts and lowers their
sales value. Drying can be hastened
by placing the pelts in a small room
equipped with a circulating fan;
after about 3 days they can be re-
moved, strung in bundles of 25, and
hung in a shed for more leisurely
completion of the drying process.
Pelts exposed to rain or dampness
mold quickly. In the southern
States, good results are obtained by
drying the skins on racks in the
open air; but a hot sun will dry
them too rapidly, causing them to
shrink and, frequently, to grease
burn.

Figure 46. — Mu.skrat iielts on modern
wire stretchers hung in tiers to dry.

Figure 47. — Many Louisiana trappers
hang the pelts on outdoor racks to dry.
The short, squared-ofE appearance of
the pelts is due to the skinning method
and type of wire stretcher used.

32

black (a very dark or black color
phase of the brown) ; and (3) the
Louisiana, or southern.

There are several methods of
grading muskrat pelts and few peo-
ple sort thorn in the same way.
They are usually classified accord-
ing to (1) size group — mice and
kits, small, medium, large, x large,
XX large, and xxx large; and (2)
season — fall, winter, and spring.
They are further graded on condi-
tion, such as flats, damaged, and
tainted, and on color quality.

In former years, many muskrat
skins were home-tanned and made
into caps, gloves, coat collars, and
other articles. The process is very
tedious and requires excessive hand
labor, so that very little of this is
now done in the home. Today,
practically all pelts are tanned and
dressed in the large centers of the
fur trade : New York, Newark,
N. J., St. Louis, Mo., and Seattle,
Wash.

Burlap sacks have proved highly
satisfactory for shipping muskrat
skins. When large quantities of
skins are shipped long distances to
market, they are usually put in spe-
cial presses and baled. The pelts
must be thoroughly dry and the
bales should be held in cold storage
to prevent molding and grease
burns.

Muskrat Meat as Food

Although the muskrat is trapped
primarily for its pelt, its flesh is
highly esteemed by many (fig. 48).
Several million are eaten annually,
but the poor utilization of this im-
portant source of meat represents
an enormous waste — it could be

Figure 48.— A dish of muskrat, or
"marsh rabbit."

made to yield an additional and
profitable economic return to the
trapper and marsh-owner. Musk-
rat meat can be sold cheaply as the
additional labor required to prepare
it for market is slight.

In the retail markets of many
cities in the East and Middle West,
such as Philadelphia, Wilmington,
Baltimore, Washington, Detroit,
and St. Louis, there is a growing
demand for muskrat meat. It is
generally sold as "marsh rabbit"
but no attempt is made to conceal
the source of the meat. Muskrat
meat is becoming more popular each
season ; and throughout the trap-
ping season it is shipped to a num-
ber of large commission and pro-
duce houses. In the East it comes
mostly from the lower Chesapeake
Bay region, but occasional ship-
ments have arrived in excellent con-
dition from Louisiana and other
distant points.

For years muskrat has been
served in many of the leading hotels
and restaurants of the larger cities
under such names as "'marsh hare''
or "Chesapeake terrapin."' The
flesh is dark but fine-grained and,
with a minimum of cooking, it is

33

always tender. The meat is usually
soaked overnight in slightly salted
cold water preparatory to cooking
it.^ The flavor has often been com-
pared to that of wil^ duck and
terrapin, but it has a distinctive
gamy taste. Weak vinegar is used
to reduce this wild flavor and to
make the meat tenderer. However,
some like the natural flavor of
muskrat meat and prefer a limited
amount of seasoning. To many,
during the season, a Sunday dinner
of muskrat is preferable to one of
fried chicken. For thousands of
trapper families in many sections
of the country it is the best meat
available for their daily diet. It is
important to remove the musk
glands as they may impart a strong
musky flavor when cooked with the
meat.

MUSKRAT FARMING

The increasing demand for musk-
rat fur has led to considerable
public interest in the possibilities
of raising this animal commercially
in pens and fenced enclosures.
Numerous artificial muskrat farms
were promoted in various States
during the period 1925 to 1930.
Many persons were deceived by
statements that muskrats could be
produced profitably under such
conditions, and the vast majority
of these ventures proved unsuccess-
ful. Caution should govern any
attempt to raise muskrats in this
manner.

Raising Muskrats in Pens

Although muskrats can be raised
on a limited scale in pens, it is not
profitable. Reproduction under re-
straint is irregular and losses result
from fighting, drinking polluted
water, and the close handling neces-
sary to raise the animals (fig. 49).
After many generations of pen rais-
ing, muskrats still reniain wild and
easily excited. They never become
tame enough to be handled or to be
trusted.

The practice of pairing off the
animals before the start of the
breeding season should be followed
as much as possible. After a musk-
rat becomes established in a breed-
ing enclosure, it often resents the
introduction of a strange animal,
even of the opposite sex, and fatali-
ties occur. In the early attempts at
pen breeding considerable stock was
lost in this manner, the female often
being badly slashed and cut over
the rump.

The investment required in equip-
ment and stock, and the cost of food
and labor, make it difficult to realize
a profit on the sale of muskrats for
the pelt value alone. Ranching
operations, consequently, are lim-

' Dozier, Herbert L., Recipes for cook-
ing muskrat meat, Wildlife Leaflet 229,
U. S. Fish and Wildlife Service, Wash-
ington, D. C.

Figure 49. — Pens built in the marsh to
study the breeding and feeding habits
of the muskrat.

34

ited to producing animals to sell for
breeding or restocking. At present,
little is known of the possibilities of
selective breeding of muskrats.
Certain of the color mutations, par-
ticularly the black-and-tan phase,
might possibly change the present
picture and make pen raising of
muskrats worth while if a strain of
selective, persistent breeders under
confinement develops.

Raising Muskrats on Natural and
Fenced Areas

The landowner with a marsh,
pond, stream, or swamp should con-
sider the possibilities of raising
muskrats as an added source of in-
come. They require no special feed-
ing— the plant life of such areas
generally supplies an abundance of
food — and they increase rapidly
when given a minimum of attention
and protection.

A marsh in which there is a pond
with running water and a lush
growth of bulrushes, cattails, water-
lilies, and other aquatic plants, is
ideal for muskrats. While a heav-
ily wooded swamp has the necessary
water, usually it does not produce
sufficient food for a large muskrat
population. There is scarcely a
farm, however, that does not have
drainage ditches, or a small amount
of low, submarginal land, or a creek
w^hich yields muskrats.

Unless forced to leave because of
floods, droughts, or hunger, musk-
rats as a rule remain fairly close to
their feeding grounds and homes.
Large muskrat-producing areas,
therefore, do not usually need to be
fenced. Natural boundaries, tres-

pass laws, and continuous surveil-
lance tend to control poaching.

Fencing may be advisable in some
instances but is costly on large
areas. It reduces poaching, pre-
vents the escape of the animals, and,
when correctly done, reduces pre-
dation. Galvanized, 1-inch mesh,
16-gage wire is suitable and lasts
for years except under salt-water
conditions. Sinking the fence from
10 to 12 inches below the surf ace. is
usually sufficient on dry ground ; in
marshes and swamps it must go
much deeper. Steel posts are satis-
factory on high, dry land, but
wooden or concrete posts are more
serviceable in muck or on wet
ground.

Supplemental feeding may be
necessary in fenced areas, where
food is limited. Muskrats are fond
of corn, either dried or green, car-
rots, cull apples, crimson or scarlet
clover, raw peanuts, alfalfa, Swiss
chard, Jerusalem artichokes, cab-
bage, lettuce, curly kale, vetch,
kudzu vine, and sunflower. Tur-
nips, sweet potatoes, parsnips, beets,
squash, pumpkins, and red clover
are accepted at times but are not
greatly relished.

Farm Ponds in Relation lo
Muskrats

In a properly constructed and
well-managed farm pond, muskrats
will usually provide an additional
source of income without interfer-
ing with other uses of the pond.
Muskrats dig in the banks or dam
primarily to make dens and they
select the steepest slopes and the
heaviest vegetation. The banks of
the pond should always he cut to a

35

slope steeper than that of the dam
wherever soil conditions will per-
mit, and root stock of durable food
plants should be used to provide a
dense vegetation covering. The
watershed or flow into the pond, as
well as the size of the spillway,
should be adjusted so that the water
level remains fairly constant, with a
rise of not more than 6 or 8 inches.

Stocking Depleted Areas

Some part of practically every
section of the United States is
adapted to the raising of muskrats.
There are many extensive areas on
which few or no muskrats occur,
owing in most cases to outbreaks
of disease, destructive floods, high
tides, overtrapping, or prolonged
droughts at some previous time.
Many of these areas have the neces-
sary food and water and, if stocked
with muskrats and carefully man-
aged, could be made to pay the
owner good dividends.

Muskrats should be stocked only
after careful study. The wide vari-
ation between the several races re-
quires serious thought on the many
angles involved : differences in size,

S>r and pelt quality, litter size,
reductive capacity, adaptability,
and temperament. The possible in-
troduction of parasites and diseases
must also be considered.

Many commercial shipments of
muskrats for stocking purposes
have been made in past years to
various parts of the United States
and Canada, as well as to points in
the Old World. Some have been
desirable and successful, others
have had poor or questionable re-
sults. One firm in Maryland sold

some 50,000 wild muskrats for re-
stocking purposes between 1915 and
1944. Undoubtedly, the size of
some of those shipments greatly re-
duced local muskrat populations.

The introduction of 22 pairs of
muskrats {Ondatra z. zibethicus)
from Michigan to the Tule Lake
(Calif.) area in 1930 and their
rapid increase in less than a decade
(31,252 were trapped in the 1939-40
season on the Tule Lake National
Wildlife Refuge) is an outstanding
example of the effectiveness of re-
stocking when combined with good
management. About 700 pairs of
muskrats involving both the brown
and the black-and-tan color phases
were placed on a 1,500-acre marsh
near Moyock, N. C, in 1936; more
than $5,000 worth of pelts were
trapped off the area 3 years later.
The muskrats came from near
Church Creek, Md., and were of the
same race, Ondatra z. macrodon^ as
those that had formerly occupied
the North Carolina marsh. The
financial returns would probably
have been even greater had only the
black-and-tan color phase been re-
leased, as the "Maryland black"
normally commands a better price
than the brown.

LIVE-TRAPPING MUSKRATS

Numerous attempts to obtain
muskrats for stocking purposes di-
rectly from trappers during the
open season have had disappoint-
ing results. Animals caught in
steel traps usually tear loose and
injure a leg or the shoulder muscles
so severely in struggling to escape
that they finally die. Skinning re-

36

1»v

Figure 50. — Left : Collapsible wire trap used in live-trapping muskrats, placed in bank
lead to a den. Center : Same type of trap set on top of a muskrat house. Right :
Muskrat caught in a Gibbs net trap.

veals the bruised, bloodshot areas
beneath the skin. When caught by
a toe tip or by the tail and not un-
duly exposed to sun or cold, a musk-
rat usually recovers; but those
trapped by the foot or the leg
nearly always lose it, even though
they, survive the shock and infection
which follow.

Live-trapping of muskrats is
often exceedingly difficult, espe-
cially under summer conditions.
Despite careful handling there is
usually considerable mortality in
the traps from exposure or injury,
and such animals must be skinned
for the pelt. A variety of live traps
have been used but none is com-
pletely satisfactory. The most suc-
cessful and widely used is a col-
lapsible, rectangular, treadle-type,
wire trap that can be used in bank
leads and runways or on top of
muskrat houses (fig. 50), Baits of
carrots, apples, and corn are often
used, but in southern marshes where

food is ample the year-round, they
are less effective.

On some marshes where bank
muskrats are present, it is possible
to dig out the burrows and take un-
injured animals. In clay hardpan,
with little or no peat, and a maxi-
mum water level of 4 inches, stop-
ping up the runs and breaking open
the houses is often the most prac-
tical and economical method. The
rough vegetation should be burned
off, all runs plugged, and the sur-
rounding tunnels stamped in. The
nest material is cleared away with a
potato digger to reveal the plunge
hole, and the muskrats are easily
caught when they stick their noses
above water for air.

Handling Live Muskrats

High mortality generally accom-
panies attempts to hold and trans-
port live muskrats (fig. 51). Ex-
cept in cold weather, the animals
cannot be held in any numbers in an

37

I '

'-,1

FiGURK 51.— Pen for holding muskrats
temporarily in the field when live-
trapped. An elevated, dry compart-
ment prevents undue exposure. Note
manner of holding the muskrat.
(Courtesy Idaho Fish and Game De-
partment. )

enclosure without serious loss from
fighting. During the winter quite
a number can be allowed to use the
same run after a few days of ad-
justment ; as many as 15 or 20 adults
have been seen curled up on top of
each other inside a nest box during
periods of low temperatures. As
spring and the breeding season ap-
proach this is impossible without
fighting.

Despite careful handling many
live-trapped muskrats are lost and
the reasons are not always readily
apparent. Particular attention
should be given to the following
points :

1. Muskrats are handled most easily
by carefully picking them up by the tail
near the tip ; avoid sudden jerks which
can dislocate the vertebrae and result
in paralysis of the hind quarters.

2. The region about the nose is es-
pecially sensitive to the slightest blow ;
death may result from fracture of the
delicate bone structure and from con-
cussion.

3. The muskrat cannot stand long
exposure to extreme temperatures

above water. Intense sunlight, heat,
or cold can cause death very quickly.

4. Many muskrats die from non-
apparent injuries sustained in traps,
such as internal bruises and torn
tissues.

5. The muskrat usually is not a vi-
cious animal when properly handled,
but it is highly excitable ; and animals
from the same litter often seriously
injure each other when excited. It is
remarkable how easily one can with its
sharp incisors kill another.

Banding and Tagging

Experimental studies to deter-
mine the radius of spring dispersal,
normal range and mass movements,
growth rates, and longevity, re-
quire the banding or eartagging of
the trapped muskrats before their
release. Of all the types of bands
tried by the various investigators,
the Achilles-tendon method of at-
tachment has proved the best. Most
banding methods can cause serious
injury and even loss of the muskrat,
and have been discarded in favor
of eartagging (fig. 52). The Al-
dous holding device has greatly
simplified the process. By this in-

FioiTRE. 52. — A small, metal, numbered
tag attached to the ear of a nmskrat
is generally used in experimental
studies.

38

genious device, the muskrat can be
held firmly by gentle pressure on
the plunger, the ears pulled through
the wire netting, and the tag quickly
attached, without, unduly squeezing
or bruising the animal a^nd without
risk to the operator. A small, num-
bered eartag, made of aluminum or
preferably Monel metal, is in gen-
eral use.

Identification of Sex

For efficient management and re-
stocking, recognition of the sex of
the muskrat is essential. No valid
criteria of color or size exist for the
sexes, but the sex of an adult musk-
rat can be determined by palpation.
The animal is picked up by the tail
and lowered until its front feet rest
on a firm surface such as a board or
table. Held in this position for a
few moments, it usually calms down
(extreme caution is necessary in
handling the muskrat, for it is very
agile and will turn and bite
quickly). The sex can then be de-
termined by palpating the genitalia.
A protuberance, or urinary sheath,
is present in both sexes; it lies on
the ventral midline, anterior to the
anus, and covers the penis in the
male and the anterior rim of the
vaginal entrance in the female.
The relatively long and solid penis
of the adult male can be felt within
the sheath. The protuberance in
the male is long and somewhat
rounded; in the female it is less
conspicuous, more pointed, and
comparatively short. The vaginal
opening is often difficult to see in
nonbreeding females ; it may be cov-
ered by a vaginal closure mem-
brane. In adult females during

the breeding season the vaginal
opening is prominent.

The most convenient criteria for
determining sex in muskrats are
(1) distance between the anus and
the protuberance, and (2) presence
of hair over a portion of this area
which is known as the perineum.
In the male the perineum is long
and is covered with hair; in the fe-
male it is short and the anterior
part is hairless.

Shipping Live Animals

The shipper of live muskrats
must see that the animals are well
crated to insure arrival at their
destination in a good condition.
Shipping crates should be made of
20-gage sheet metal or of wooden
boxes lined with hardware cloth or
netting to prevent the muskrats
from gnawing their way out (fig.
53). Each muskrat should be
shipped in a compartment of ap-
proximately 101/2 X 81/2 X 101/2
inches. Separating the animals
keeps them from injuring each other
by fighting, which results from in-
compatibility and the excitement

Figure 53. — Metal cages such as these
have proved very satisfactory for
shipping live muskrats.

39

caused by jolting in transit and mov-
ing of the crate at transfer points.
Each compartment should have a
securely fastened water container
and sufficient nest material or straw
to prevent exposure, Muskrats are
especially susceptible to pneumonia
while in transit. Crates should be
labeled "Keep out of sun and away
from intense heat." Shipments
should be made during cool weather
whenever possible, as animals suffo-
cate easily during periods of intense
heat.

Several ears of dried corn, a few
carrots, and a head of cabbage or
lettuce placed in each compartment
should be ample food for a muskrat
traveling a long distance. Success-
ful shipments have been made in
this manner from Maryland to Lou-
isiana, across the continent, and to
foreign countries. If muskrats are
moved by car or truck, care must
be taken to prevent their suffocation
or asphyxiation by exhaust fumes.

RECOMMENDATIONS

A high, sustained annual yield is
the primary objective of commer-
cial muskrat production. To attain
this objective close adherence to the
following basic principles of marsh
management is necessary :

Maintain water levels at a depth
conducive to the best growth of
desirable muskrat foods, such as
the cattails and bulrushes. A di-
rect correlation exists between the
abundance and quality of food
present on a marsh and the number,
size, and weight of the muskrats
produced there. In general, both
the muskrats and their favorite
food plants require rather shallow

water. Under northern conditions
the water must be deep enough to
prevent winter freeze-outs. An
ideal water condition is one in
which three-fourths of the marsh
is covered by water 18 inches or less
in depth, with numerous deeper
ponds, holes, and ditches inter-
spersed throughout the marsh.
Maintain stable water levels. Ex-
treme fluctuation in water levels is
very damaging to muskrats and
other wildlife, as well as to their
food plants. Water-control struc-
tures should be so designed that the
water levels can be raised or low-
ered as the need arises.
Use all sources of fresh water,
such as rainfall and runoff from
fields, woods, and drainage
ditches. Muskrats generally pre-
fer fresh to slightly saline water.
Prolonged droughts and high tem-
peratures increase salinity. In the
Gulf Coast region the most-produc-
tive muskrat areas are the brackish-
water, three-square marshes.
Storms and high tides often destroy
the favorite food plants of the
muskrat and exert a harmful effect
on the animals themselves.
Use controlled burning judi-
ciously. Although an important
factor in muskrat production, con-
trolled burning must be done only
when the water level in the marsh
is such that deep root burns will not
result to desirable food plants. At
least 3 inches of water should be
present over most of the area at
time of burning. Burning may be
used to remove the "rough"' and to
open up dense stands of undesirable
emergents, such as sawgrass (67a-
dium jcmiaicense) .

40

Remove the annual crop of musk-
rats at the right time and in
amounts compatible with the
numbers present on the marsh.

An estimate or census, should be
made each year, just before the legal
trapping season, as a basis for
planned removal of the surplus and
determination of population trends.
Muskrat crops- cannot be held over
a long period for harvesting in a
single season. Whenever their
density reaches one dwelling house
to an acre, trapping should be un-
dertaken. A density of 2.5 houses
an acre calls for immediate heavy
trapping; if action is delayed at
this time "eat-outs" invariably re-
sult in spite of intensive trapping
later. To maintain a proper bal-
ance between the muskrats and their
environment, approximately two-
thirds of the population should be
removed each year.

Analyze the composition of the
catch made during the trapping
season. Sex ratios and distribution
of the age classes of the trapped ani-
mals provide an excellent index to
population trends. An abnormally
high take of adults indicates little
or no breeding that season or poor
survival of the young. A low pro-
portion of adults is indicative of
close trapping or overtrapping in
the preceding or current year.

Select trappers carefully. Trap-
pers should be experienced, reliable,
and energetic. Trap lines should be
run daily, preferably early in the
morning. Knowledge of the habits
of the muskrat and suitable equip-
ment are necessary to efficient trap-
ping.

Assign to a trapper only as much
acreage as he can manage; and
make the catch quota liberal
enough to avoid undertrapping.

The "yield-per-house" is a much
better measure of trapping effi-
ciency than the "yield-per-acre."
Overtrapping can occur under some
situations, but it has been the ex-
perience of trappers and marsh-
owners generally that it is almost
impossible to overtrap a normal
muskrat population. It is far bet-
ter to overtrap an area than to un-
dertrap it.

Keep populations of predators, as
foxes, raccoons, and minks within
reasonable limits. The annual
drain on the muskrat by predators
may become very serious. Their
control will lead to larger muskrat
crops and a reduction in the num-
ber of damaged pelts. By removing
such animals during the legal trap-
ping season additional revenue can
be realized from the sale of their
pelts.

Drain "eat-outs'* promptly. To

correct "eat-outs," drainage ditches,
usually about 30 inches wide and
deep, should be cut across the marsh
to carry the water from the de-
nuded areas. This permits the sun-
light to reach the mud bottom and
creates better conditions for seed
germination and the survival of any
pieces of rootstalks remaining.
Closed or blind ditches are pre-
ferred and should be so constructed
that salt-water intrusion is pre-
vented in coastal marshes.

Use cattle grazing cautiously. In

general, muskrats and cattle do not

41

go together ; the cattle continually grazing plus temporary drainage to

trample the muskrats' nesting be fully effective in "deep marshes."

houses and runways and damage Conditions in heavy sawgrass for-

trap sets. Grazing has been used mation make it exceedingly diffi-

at times to open up dense stands of cult for cattle to graze, and the f oli-

bulrush and giant cutgrass to pro- age, except tender new recovery

duce better muskrat and waterfowl growth in burns, is very unpala-

areas, but this requires capacity table.

42 U.S. GOVERNMENT PRINTING OFFICE :0 — 1953

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5 WHSE 00082