Ermine or Weasel
Ermine have a circumpolar distribution.
They are found in the north temperate regions of Eurasia and North America.
In the New World, they range from east to west in a broad belt from the
Arctic Ocean and adjacent islands of the Canadian Archipelago southward
into the northern United States. Ermine are absent from the Great Plains.
Ermine prefer riparian woodlands,
marshes, shrubby fencerows, and open areas adjacent to forests or shrub
borders. Although ermine are primarily terrestrial, they climb trees and
swim well. Tree roots, hollow logs, stone walls, and rodent burrows are
used as dens. Dens are usually around 300mm below ground. Ermine line their
nests with dry vegetation, and fur and feathers from prey. Side cavities
of burrows are used as food caches and latrines. (Ruff and Wilson, 1999)
Mass: 25 to 116 g (0.88 to 4.08 oz)
Length: 170 to 330 mm (6.69 to 12.99
At full adult size total body length
from head to rump is 170mm to 330mm. Males are generally twice as large
as females, with males weighing from 67 to 116 grams and females from 25
to 80 grams. The tail length is about 35% of the total body length, ranging
from 42mm to 120mm. Ermine have the typical weasel form: long body, short
legs, long neck supporting a triangular head, slightly protruding round
ears, bright black eyes, and long whiskers. Their short, moderately fine
fur is white in the winter and the tip of the tail is black. In the summer,
the dorsal fur is chocolate brown while the ventral fur extending to the
upper lip is yellowish white.
Breeding interval: Ermine generally
breed once yearly.
Breeding season: Ermine mate in late
spring to early summer.
Number of offspring: 3 to 18; avg.
Gestation period: 280 days (average)
Time to weaning: 8-10 weeks (average)
Age at sexual or reproductive maturity
(female): 60-70 days (average)
Age at sexual or reproductive maturity
(male): 2 years (average)
Ermine are a polygynous-promiscuous
species, with males and females mating opportunistically.
Ermine mate in late spring to early
summer. Females are polyestrous, but produce only 1 litter per year. Young
are born in April or May after an average gestation period of 280 days,
which includes an 8-9 month period of developmental delay. Longer days
beginning in March trigger the resumption of fetal development. Litter
size ranges from 3-18 offspring and averages 4-9. The sex ratio is unequal.
Young are blind and helpless. They are covered with fine white hair, and
a prominent dark mane of dense fur develops around the neck by the third
week (function unknown). The young grow quickly and are able to hunt with
their mother by their eighth week. Although females do not reach adult
size until a least 6 weeks after birth, they are able to mate when they
are 60-70 days old, often before they are weaned. Males do not breed or
gain adult dimensions until their second summer.
Females in nature may survive for
at least 2 breeding seasons, while males generally do not survive this
long. Reproductive success is highly dependent on food availability.
Females exclusively care for their
offspring, nursing and protecting them until they become independent. The
young are born blind and helpless.
Longest known lifespan in wild
7 years (high)
Expected lifespan in wild
1-2 years (average)
The ermine's lithe, agile body allows
it to move swiftly both above ground and through underground burrows. Females
hunt in tunnels more than males, which may explain the higher number of
males that are trapped. Ermine can also run easily across snow. This ideal
predator hunts in a zigzag pattern, progressing by a series of leaps of
up to 50 cm each. Ermine investigate every hole and crevice, often stopping
to survey their surroundings by raising their heads and standing upright
on their hindlegs. They may travel up to 15 km in one night.
Adult males dominate females and young.
Females tend to remain in their birth place throughout their lives. Males
disperse and attain large territories that usually encompass or overlap
Male and female ermine only associate
with one another during the breeding season.
Ermine population densities fluctuate
with prey abundance. When conditions are good, an individual may occupy
a 10ha area. The maximum home range size is about 20ha. Home ranges of
males are usually twice the size of female home ranges. These solitary
mammals maintain exclusive boundaries that are patrolled and marked by
scent. (Ruff and Wilson, 1999)
Communication and Perception
Ermine have keen senses of smell,
vision, hearing, and touch that help them to locate prey. Most mustelids
are fairly quiet animals, but some vocalizations may be used in intra-specific
communication. Chemical cues are probably the main means of communication
reproductive readiness to potential mates.
Ermine are carnivores that hunt primarily
at night. They are specialist predators on small, warm-blooded vertebrates,
preferably mammals of rabbit size and smaller. When mammalian prey is scarce,
ermine eat birds, eggs, frogs, fish, and insects. In severe climates, ermine
frequently hunt under snow and survive entirely on small rodents and lemmings.
Daily meals are essential to meet the ermine's exhorbitant energy and heat
production demands. Ermine cache leftover meals as a way of dealing with
these demands. (Ruff and Wilson, 1999)
Once a potential prey is identified,
the ermine approaches as closely as possible. With incredible speed it
grasps the back of the victim's head and neck with sharp teeth, and wraps
its body and feet around the victim. The victim dies from repeated bites
to the base of the skull. Ermine have keen senses that help them locate
prey. Hares and rodents are mainly followed by scent, insects by sound,
and fish by sight. (Ruff and Wilson, 1999)
Ermine are fierce and agressive, although
diminutive, animals. Potential predators are larger carnivores including
red fox, gray fox, martens, fishers, badgers, raptors, and occassionally