IDENTIFICATION
of
MUSKRAT
KINGDOM: Animalia
PHYLUM: Chordata
CLASS:
Mammalia
ORDER:
Rodentia
FAMILY:
Muridae
GENUS:
Ondatra
SPECIES:
Zibethicus
IDENTIFICATION (cont.)
Total length:
545-640mm (21-25”)
Tail length:
250-283mm (9-11”)
Hind foot length: 65-78mm (2.5-3”)
Ear length:
Weight:
Neonates:
20-21mm (~1”)
700-1800g (1.3-4 lbs.)
~ 21g
IDENTIFICATION (cont.)
Generally, dark brown
Fur color can vary from white & silver through
tan, reddish-brown, and black
Ventral pelage lighter than the rest of the fur
Tail and feet are usually dark brown or black
IDENTIFICATION (cont.)
Total of 16 teeth
Incisors: 1 pair
Canines: 0
Premolars: 0
Molars: 3 on each side
Dental formula: I-1/1, C-0/0, P-0/0, M-3/3=16
TAIL
Flattened and scaly
EYES
Top of the head allowing it to see
above water while swimming.
TRACKS and SCAT
BIOLOGY
Scent glands: two at the base of the tail (hence the name
muskrat)
Tail: scaly, flattened, serves as a rudder when swimming
Feet: partly webbed hind feet, with short stiff hairs lining
the toes, called the ‘swimming fringe’
Swimming: can swim at a rate of 1.5-5km/hr, can swim
backwards, & can stay submerged for up to 20 minutes
BIOLOGY (cont.)
Pelage: layer of soft, dense underfur interspersed
with long, coarse guard hairs. The underfur is
waterproof, and a layer of trapped air in the nonwettable fur enhances the buoyancy and insulation.
Annual molt: begins in the summer, minimum
density in August
BODY TEMPERATURE
Tail: helps with thermoregulation by functioning
as a heat sink
Wika & Pasche: heat loss through the tail is
proportional to the temperature gradients between
the tail and the environment
Prevent loss of body heat:
-get out of the water
-increase abdominal temp.
LIFE HISTORY
Generally promiscuous
Males compete fiercely for mates
Sexually active spring after birth
Spermatogenesis begins in early spring and lasts into late autumn
Vaginal orifice is sealed from birth and opens just before breeding
activity
Estrus cycle: 3-6 days
Gestation period: 25-30 days
Litter size: 4-8 (mean of 6 or 7)
LIFE HISTORY (cont.)
Litter size and number influenced by:
-latitude
-southern latitudes: more litters/year
-habitat quality
-poorer habitat produce fewer litters
and smaller sizes
LIFE HISTORY (cont.)
NEONATES:
Blind
Hairless
Pink or gray in color
Rounded tail
LIFE HISTORY (cont.)
YOUNG:
Covered with soft fur
Swim within 14 days
Tail becomes compressed during 2nd month
Weaned at 4 weeks
Males grow faster than females
Average life is only 2-3 years
ECOLOGY
FEEDING: Omnivorous
PREY: amphibians, snails,
crustaceans, mussels,
turtles, fish, roots and
leaves of hydrophytes
ECOLOGY (cont.)
PREDATORS:
Raccoons
Red foxes
Wild dogs
Bald eagles
Great-horned owl
Red-tailed hawk
Hunters/trappers
ECOLOGY (cont.)
HOUSING LOCATIONS:
Conical houses
Dig burrows into banks
Push-ups over icecracks
TYPES OF HOUSES:
Main dwelling house
Feeding house
HOUSING DESIGN/ARCHITECTURE:
Site selection influenced by: water depth, soil texture, amount of
aquatic vegetation
Begin building in May/June, October
Large lodges of vegetation—will live in small family groups
Multiple lodges in an area—up to 5 muskrats/lodge
Construction begins on firm substrate, w/dominant emergent
vegetation
Houses built above the water level
Several underwater tunnels
Nest chambers lined with fresh plant material
HOUSING (cont.)
Temperature inside houses higher than surrounding
temperature
“Huddling”-increases the temperature, increasing
survival during the winter
HOME RANGE:
Small home range
Within 15 m of their primary dwelling
Foraging usually within 5-10 m of lodge or push-up
Move greater distance on rainy days
DISPERSAL:
Occurs in March/April
Dispersal initiated by:
Snow
Ice
Air temperature
Population density
Sex/age composition
Forced movements caused by floods, drought, intraspecific
strife
DISPERSAL (cont.):
After dispersal, usually return to their home range
Study by Mallach:
500-2,000 m away-----57% returned
3,000 m away----------31% returned
4,000 m away----------15% returned
DISEASES:
-Adiaspiromycosis
-Ringworm disease
-Epizootic disease
-Salmonellosis
-Hemorrhagic disease
-Tuluremia
-Leptospirosis
-Tyzzer’s disease
-Pseudotuberculosis
-Yellow fat disease
PARASITES:
-36 trematodes
-19 nematodes
-13 cestodes
- 2 acanthocephalans
-17 acarina
ENDOPARASITES:
-Trematodes:
-Echinostoma revolutum
-Plagiorchis proximus
-Quinqueserialis quinqueserialis
-Nematodes:
Trichuris opaca
-Cestodes:
-Hymenolepsis spp.
-Taenia taeniaeformis
*little impact, except Taenia taeniaeformis (tapeworm)- causes
females to produce fewer young
ECTOPARASITES:
-mites
-ticks
*can cause skin rash, but generally not fatal
POPULATION
STATUS
Solid population
throughout N. Am., as
well as in KY.
Occur from the
Yukon & NW
Territories to the Gulf
of Mexico, and from
the Aleutian Islands
east to the Atlantic
coast, and south to N.
Carolina
POPULATION (cont.)
Muskrat population generally follow a 10 year cycle.
An increase in muskrat population is often followed
by an increase in mink population a year later, and an
increase in mink population is generally followed by a
decrease in muskrats a year later.
Population is estimated based on the fur harvest.
Muskrat houses can be used to estimated population
densities.
They are not threatened or endangered.
WETLAND HABITAT NEEDS
Fresh and Saltwater marshes, swamps, river
banks, ponds, lakes
Nest in bulky nests of plants on open swampland
Also nest in tunnels dug into river banks above
the high water mark
WETLAND HABITAT NEEDS (cont.)
Require aquatic vegetation for food and for
housing material
Food such as snails, crustaceans, mussels, turtles,
fish
MANAGEMENT CONCERNS
The most valuable semi-aquatic furbearing mammal,
with the pelt industry in the millions of dollars
RUSSIAN HAT
BOMBER HAT
MANAGEMENT CONCERNS (cont.)
Mgmt. Practices to increase muskrats:
Create marshes, ponds
Don’t destroy wetlands for agriculture
Control water levels on marshes with an irregular water source to
encourage growth of favored plant species
Construct level ditches in shallow marshes to ensure adequate
water depths during winter
Controlled burning during early spring to prevent buildup of dead
vegetation and release nutrients into the ecosystem
Fence off all except a small portion of ponds, creeks, and
wetlands on farms where livestock are kept to prevent grazing and
trampling of the shoreline
MANAGEMENT CONCERNS (CONT.)
PROBLEMS:
Garden damage
Overgraze marsh vegetation
Burrow holes under dams and dikes
Cause damage to irrigation canals & farm ponds
“Eat-outs”-the extensive loss of vegetation &
resulting silting that makes the areas less
productive for other species of wildlife
MANAGEMENT CONCERNS (cont.)
OVERPOPULATION REMEDIES
Treat garden plants with ROPEL
Gassing/poisoning
Shooting/trapping
Water drawdowns or burning
“Rip-rap” banks with crushed stone
MANAGEMENT CONCERNS (cont.)
KY HUNTING/TRAPPING REGULATIONS
All furbearer hunting/trapping:
Raccoon, opossum, mink, muskrat,
beaver, red fox, gray fox, weasel, striped
skunk
Noon 11/10/03 - noon 2/29/04
no hunting or trapping bag limits
IDENTIFICATION OF NUTRIA
Order: Rodentia
Family: Myocastoridae
Genus: Myocastor
Species: Coypus
DESCRIPTION
SIZE
Head and body: 22-25”
Tail:
12-17”
Weight:
10-30 lbs
DESCRIPTION (cont.)
Pelage: soft dense underfur and long, coarse
guard hairs. Underfur is densest on the
abdomen and thickest during the winter.
Pelage color: yellow-brown to dark-brown,
with the chin covered by white hairs. The tail
is scantily haired.
Long, round tail
DESCRIPTION (cont.)
FEET
First 4 digits of the hind feet are webbed
5th toe is free and used in grooming
Front digits are strongly clawed
Pollex is reduced
Soles of the feet are hairless
BIOLOGY
Female has 4 or 5 pairs of mammary glands
located dorsally, which allows for suckling young
while swimming
An oily secretion from glands located at the base
of sensory bristles near the mouth and anus
lubricates the pelage when grooming
These secretions are also used to delineate home
ranges
BIOLOGY (cont.)
Femur has a well developed trochanter for attachment of
the muscles involved in swimming
Well developed deltoid crest and a large scapula fossa aid
in burrowing
Nocturnal, and spend most of their time feeding,
grooming, and swimming
Become diurnal during cold periods to recover feeding
time lost while huddling at night
Can remain submerged for greater than 10 minutes
LIFE HISTORY
REPRODUCTION
Nonseasonal breeders
Peak births- Jan., Mar., May, Oct. in Oregon
Peak births- Dec.-Jan. and June-July in Louisiana
Mean litter size: 3-6 (declines during winter months &
increases when food is abundant and mild winter)
Usually have litters in open nests at the edge of a body
of water, or in large nest chambers deep in their burrows
~27% of litters are aborted
REPRODUCTION (cont.)
Young are precocial
~225g at birth
Rapidly gain weight during first 5 months
No difference in mass between males and
females at birth, but when fully grown males are
up to 15% heavier
ECOLOGY
Live in aquatic habitats- rivers, lakes, ponds, marshes, bogs
Swims well, makes shallow burrows in banks with an
enlarged nesting chamber at rear
Remain in one area throughout their life, however freezing
weather or drought may cause migration
Daily cruising range is less than 45 m
Daytime activity is influenced
by temperature, with sunning and
sleeping being the main activities
if less than 28ºC
POPULATION
STATUS
Native to South America
As a result of escapes
and liberations from fur
farms, populations now
exist around the world
By 1959, there were 20
million in Louisiana
First pelts reached the
market in 1944, and harvest
grew to 1 million pelts by
1987
WETLAND HABITAT NEEDS
Prefer river banks, marshes, ponds, swamps, bogs
Like to burrow in banks
Aquatic vegetation for food – stems, leaves, roots, and
bark (also feed on agricultural crops)
MANAGEMENT CONCERNS
Not generally a problem, except at high
densities
Disrupt drainage systems, damage crops,
disturb natural plant communities
Burrows can weaken river banks that keep low
lying land from flooding
CONTROL PROCEDURES
Shooting, trapping, baiting, chemicals
MANAGEMENT CONCERNS (cont.)
Severe cold weather can decrease pop.
S. Am. Predators-jaguar, mountain lion, little
spotted cat, caymans
La. Predators-alligators, gars, turtles, large
snakes