BIOLOGICAL DATA AND HABITAT REQUIREMENTS
WILDLIFE SPECIES: Mustela vison | Mink 



TIMING OF MAJOR LIFE HISTORY EVENTS : 
Diurnal Activity:  Mink are chiefly nocturnal but also somewhat
crepuscular [1].  In Manitoba radio-collared mink were most active at
night, with intermediate levels of activity at dawn and dusk.  They were
more active, with more extensive movements, in April than in May, June,
or July [2].

Breeding season:  In most areas the mating period occurs from late
February to early April, peaking in March [1,23].  In southern Florida,
however, mink mate in the late wet season (autumn).  Hydroperiod
determines prey abundance and availability in southern Florida, which
appear to determine breeding season.  Female mink were found to be
lactating in March and April, slightly earlier than populations farther
north [19].

Gestation and Development of Young:  Gestation ranges from 40 to 75
days, depending on pre-implantation period.  Young are born 28 to 30
days after implantation, in April or May [1,10,23].  Neonates are
altricial and have sparse, light-colored hairs.  The first teeth emerge
at 2 to 3 weeks, eyes open at about 3 weeks, and solid food is first
taken at about the same time.  By 35 days the young are fully
homeothermic.  By 7 weeks they have achieved 40 percent of their adult
body weight and 60 percent of adult body length.  Litters disperse in
early fall [23].  Females attain adult weight at 4 months; males do not
attained adult weight until 9 to 11 months [4].

Productivity:  A typical litter consists of 3 or 4 kits and ranges from
2 to 10.  The average age at sexual maturity is 12 months for females,
18 months for males [4].  Neonates have higher survival rates in warm
than in cold weather.  Mink have been reported to remain fecund for 7 or
more years [23].


PREFERRED HABITAT : 
The critical habitat feature for mink is water.  Mink prefer
streambanks, lakeshores, and marshes [10].  Habitats associated with
small streams are preferred to habitats near large, broad rivers [1].
Mink favor forested wetlands with abundant cover such as shrub thickets,
fallen trees, and rocks [10].  In aspen (Populus spp.) parklands, male
mink selected large, semipermanent and permanent wetlands with open
areas near shores, high water levels and irregular shorelines; these
characteristics are also associated with abundant avian prey [3].  Mink
are common where abundant downfall and debris creates cover for
foraging.  Logjams in streams create crayfish and fish habitat and
shelter for mink [1].  Peak mink production in baldcypress (Taxodium
distichum) swamps occurred following extensive logging in the early part
of the twentieth century.  Numbers have declined since then, probably
due to changed hydroperiod and decreased logging debris [23].  In Quebec
the majority of mink activity takes place less than 3 miles (4.8 km)
from water [6].  In Michigan all mink were observed within 100 feet
(30.4 m) of the water's edge [25].  In Minnesota all den sites were
within 231 feet (69.9 m) of open water [31].  In Idaho den sites were
16.5 to 330 feet (5-100 m) from water, and mink were never observed more
than 660 feet (200 m) from water [27].  In southeastern Alaska mink
spend the summers along streams and in upland muskegs; they spend the
winter in a narrow ocean beach zone [26].

Wetlands with irregular, diverse shorelines are better mink habitat than
those with straight, open, or exposed shorelines [1].  Marshall [25]
reported that 50 percent of mink tracks in Michigan occurred in various
stages of hydrophytic succession, 37 percent in bushy and timbered
areas, and 13 percent in sedge (Carex spp.) and common cattail (Typhus
latifolia) type.  In Alaska the highest mink densities occurred in low
swampy terrain and in extensively interconnected waterways with abundant
fish [8].

More mink are trapped in wooded swamps than in marshes.  The reported
abundance of mink in baldcypress-tupelo (Nyssa spp.) swamps is at least
partially attributable to the abundance of food [1].

In upland habitats, ecotones are most used; mink avoid open areas and
prefer shrubby, dense thickets.  Tall grass does not usually provide
adequate cover for mink; however, sawgrass (Cladium jamaicense) marshes
in Louisiana support high mink densities [1].

Mink are adaptable in their use of habitat, particularly where prey are
readily available.  They are tolerant of human activity.  Mink inhabit
suboptimal habitats if prey is available, but are more mobile and change
home ranges more frequently in suboptimal than in optimal habitats [1].

Home Range:  Mink home ranges tend to approximate the shape of the body
of water the mink uses most [1].  However, in the prairie pothole
region, mink tend to use an area rather than a linear shoreline [2].
The use of the home range varies in intensity with respect to varying
prey availability.  Mink tend to use a core area near a den site,
usually within 990 feet (300 m) of the shoreline.  They move to another
den and core area several times a season; core areas tend to be places
of relatively high prey abundance.  Usually only a small percentage of
the average or overall home range is used as the core area.  In winter
fewer den sites are used, occupancy is of longer duration, and daily
travel distances are shorter than in summer [1].

Male mink have larger average home ranges than females [1,23].  Females
tend to use a greater proportion of their home range as a core area then
males do [23].  Mitchell [29] reported the average home range for male
mink in Montana was 2 to 3 miles (3.2-4.8 km) in diameter.  Vegetative
cover has a substantial impact on home range size in Montana:  female
home ranges in heavily vegetated areas averaged 19 acres (7.7 ha),
whereas in sparse, heavily grazed areas they averaged 50 acres (20.1 ha)
[29].  In Michigan male mink average home range was less than 20 acres
(8 ha) [25].  In Idaho males used 0.6 to 1.25 miles (1-2 km) of
shoreline [27].  In British Columbia mink density on Vancouver Island
ranged from 1.5 to more than 3 mink per kilometer of shoreline [18].
Gerell [15] reported that adult male mink used an average of 8,679 feet
(2630 m) of shoreline, ranging from 5,940 to 16,500 feet (1800-5000 m).
Female adults used 3,300 to 9,240 feet (1000-2800 m), and juvenile males
used 3,465 to 4,620 feet (1050-1400 m).  

In North Dakota prairie pothole regions, mink home ranges were not
linear.  Average home ranges were 1 to 1.5 square miles (2.59-3.8 sq km)
and typically included many individual wetlands [1].  In Manitoba
prairie pothole areas, male home ranges had maximum lengths of 3.1 miles
(5.1 km) and maximum widths of 1.9 miles (3.1 km); prairie mink tended
to have larger home ranges than other mink populations [2].

Home ranges of individuals rarely overlap, with the exception of the
breeding season when male home ranges overlap those of females [1].


COVER REQUIREMENTS : 
Den sites are usually in thick cover and include hollow logs, natural
cavities under tree roots, or burrows along stream, marsh, and lake
edges [10].  Old beaver (Castor canadensis) lodges are occasionally used
as den sites [23].  In Idaho 53 percent of dens were in logjams [27].
In North Dakota marshlands, all dens were situated on shorelines and
appeared to be in abandoned muskrat burrows.  Active dens were not
located where shorelines were heavily grazed.  The absence of dry den
sites limits the use of some wetland habitats that are otherwise
suitable [1].  In Ontario dens were frequently found in areas with good
horizontal cover (31.4% obscurity at 3.5 m), and proportionally more
coniferous than deciduous shrubs.  Dens were also in areas with
higher-than-average shrub density, deadfalls, stumps, and individual
trees [30].

In Michigan mink were most commonly associated with brushy or wooded
cover adjacent to aquatic habitats [25].  In Quebec mink were normally
most active in wooded areas immediately adjacent to a stream channel
[6].


FOOD HABITS : 
Mink are almost exclusively carnivorous.  They are excellent swimmers
and pursue both aquatic and terrestrial prey.  Mink diets vary with
season, habitat, and availability of prey [1].  No single food item is
consistently more important than others [23].  Commonly important items
include common muskrats (Ondatra zibethecus), voles (Microtus spp.),
cottontails (Sylvilagus spp.), fish (mostly Salmonidae), birds, frogs,
salamanders, crayfish, clams, and insects [1,10,23].  Carey [9] listed
mink as a common predator of Townsend's chipmunks (Tamias townsendii) in
the Pacific Northwest.  Allen [1] listed mink prey preference in the
following order:  1) aquatic prey, including fish and crayfish, 2)
semi-aquatic prey including waterfowl and water-associated mammals such
as common muskrat, and 3) terrestrial prey including rabbits and
rodents.

In Idaho fish comprised 59 percent of mink diets [27].  Birds are
important prey where fish and crayfish are scarce.  In Louisiana
crayfish are so prominent in mink diets that their abundance largely
determines mink population size [1].  In Alaska coastal populations of
mink tend to be higher than inland populations due to the ready
availability of prey in tide pools [1].  Eberhardt and Sargeant [12]
reported that mink diets in North Dakota prairie marshes were dominated
by birds (78%); other prey included mammals (19%), amphibians (2%), and
reptiles (1%).  Of the avian prey, the majority were waterfowl including
American coot (Fulica americana), ducks (Anatidae), and grebes
(Podicipedidae) [12].  In southern Manitoba mink are important nest
predators of waterfowl [11].  In North Dakota mink predation on
ducklings typically occurs in semipermanent wetlands [1].

Seasonal Variation in Diet:  Shallow water and low flow rates contribute
to effective aquatic foraging by mink.  Mink tend to eat more fish in
winter when fish are more accessible.  In autumn terrestrial mammals
tend to increase in importance as prey.  Terrestrial mammals comprised
43 percent of mink diets in riparian areas in Idaho and comprised over
20 percent of mink fall/winter diets in North Carolina [1].  In Quebec
crayfish were the most important dietary item in summer [6].  In winter
mink hunting over ice can easily penetrate active common muskrat lodges,
but cannot get into common muskrat burrows so easily [28].


PREDATORS : 
Mink mortality due to predators other than humans is not substantial.
Occasional predators include fisher (Martes pennanti), red fox (Vulpes
vulpes), gray fox (Urocyon cinereoargenteus), bobcat (Lynx rufus), lynx
(L. lynx), gray wolf (Canis lupus), American alligator (Alligator
mississippiensis), and great horned owl (Bubo virginianus) [23].


MANAGEMENT CONSIDERATIONS : 
In Quebec Burgess [6] noted an increase in mink activity with habitat
improvement consisting of the creation of pools at least 1 meter deep by
placing logs and/or rocks into the stream channel which formed small
dams.  It was reported that 1) temperatures were similar in control and
improved sections of stream, 2) aquatic insect production was somewhat
higher in the improved section, and 3) trout and crayfish biomasses were
higher in the improved section [7].

Development of shorelines that reduces structural diversity and removes
snags and debris reduces mink activity.  Removal of downfall and other
debris from the water near shore, and reduction or elimination of
aquatic vegetation reduces crayfish production and contributes to
reduced mink activity [1].  In Ontario residential development around
lakes resulted in decreased mink activity due to loss of trees, decreased
density of shrubs, reduction of aquatic snags, and removal of submergent
and floating vegetation.  In areas undergoing development, 52 of 59 dens
were on undeveloped sections of shoreline [30].

Stream channelization has a negative impact on mink activity since
suitable prey abundance is reduced when shallow, detritus-rich sloughs
associated with meandering streams are replaced with abrupt, monotypic
interfaces between aquatic and terrestrial cover types.  In Mississippi
and Alabama comparison of mink activity was made among a newly
channelized segment, an old (55 years) channelized segment, and an
unchannelized segment of a river.  Mink track counts were highest in the
unchannelized segment, lower in the old channelized segment, and very
sparse in the newly channelized areas.  Abundance and density of
herbaceous vegetation were highest on the unchannelized segment [16].

There are controlled mink trapping seasons in 47 states and all
provinces.  Hunting is also allowed in five states as well as in Nova
Scotia [23].  Trapping rates fluctuate widely from year to year; price
and harvest are not significantly correlated.  The extent to which
trapping affects populations is not known [23].  Fur harvest records,
though not necessarily direct indications of population levels, show
that Louisiana, Minnesota, and Wisconsin produce the most wild pelts in
the United States.  Saskatchewan and Manitoba lead the numbers in
Canada.  These harvest records reflect the relative amount of wetlands
in the leading mink producing areas [1].  In southeastern Alaska mink is
the most abundantly harvested furbearer [26].

Linscombe and others [23] discuss parasites and diseases of mink.



REFERENCES : 
NO-ENTRY

Related categories for Wildlife Species: Mustela vison | Mink