Living Organisms / Animalia / Craniata / Mammalia / Carnivora / Mustelidae / Mustela / Species
Mustela nivalis - Weasel (Click photographs/illustrations: full picture & further details)
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General and References

Alternative Names (Synonyms)

  • Common weasel
  • European common weasel
  • Least weasel
  • Lesser Weasel
  • Pygmy weasel
  • Kine
  • Whittret (Scotland)
  • Bronwen (Wales)
  • Belette commune (French)
  • Mauswiesel (German)
  • Zwergwiesel (German)
  • Kleinwiesel (German)
  • Mustela rixosa (B51)
  • Mustela minuta (B51)

Alternative species names (the second part of the binomial species names): [Genus] africana; [Genus] albipes; [Genus] allegheniensis; [Genus] alpinus; [Genus] atlas; [Genus] boccamela; [Genus] campestris; [Genus] caraftensis; [Genus] caucasicus; [Genus] corsicanus; [Genus] dinniki; [Genus] dombrowskii; [Genus] eskimo; [Genus] fulva; [Genus] gale; [Genus] galinthias; [Genus] italicus; [Genus] kamtschatica; [Genus] major; [Genus] meridionalis; [Genus] minor; [Genus] minutus; [Genus] monticola; [Genus] mosanensis; [Genus] namiyei; [Genus] nikolskii; [Genus] numidicus; [Genus] pallidus; [Genus] punctata; [Genus] pusillus; [Genus] pygmaeus; [Genus] rixosus; [Genus] russelliana; [Genus] siculus; [Genus] stoliczhana; [Genus] subpalmata; [Genus] tonkinensis; [Genus] trettaui; [Genus] tonkiensis; [Genus] tretaui; [Genus] typicus; [Genus] vulgaris; [Genus] yesoidsuna; (B141).

Names for new-borns / juveniles

Names for males --
Names for females --

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General Appearance

Small, with long slender body (13-23cm), short legs and short tail (3-6cm) (B52, B142).

Similar Species

Distinguished from Mustela erminea - Stoat by: smaller size, tail shorter and not black-tipped (B142).
Sexual Dimorphism Male twice as large as female (1.8-2.2 times weight) (B142).

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Species Author

Debra Bourne

Major References

B51, B52, B141, B142, B143, B144, B147, B148, B221

Husbandry references:

(UK Contacts)

(Further Reading)
Click image for full contents list of ELECTRONIC LIBRARY

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TAXA Group (where information has been collated for an entire group on a modular basis)

Parent Group

  • Mustelids

Specific Needs Group referenced in Management Techniques

  • Mustelids

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Husbandry Information


Individual Techniques linked in Wildpro

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Appearance / Morphology

Measurement & Weight

Length Head-body length: 13-23cm (B142)11.4-16.0cm (B147); males mean 20.2cm, females mean 17.8cm (B142); male 26-32cm female 23-26cm (B148).
Height --
Adult weight General 25-250g (B147).
Male 70-170g mean 115g (B142); 40-250g (B52).
Female 35-90g mean 59g (B142).
New-born weight 1.5-4.5g (B142).
Growth rate Males 70-90g females 50-55g by two months old (B142).

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General --
Dentition (Teeth)
  • I3/3, C1/1, P3/3, M1/1.
  • Teeth specialised for carnivorous diet. Upper carnassials long and narrow, upper molars transversely elongated.

(B52, B142)

Eyes --

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Legs and Tracks

  • Five toes on each foot.
  • Not webbed.


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  • Reddish-brown (B142).
  • Length: 3-6cm (B142), 1.7-7.8mm (B147); males mean 6.0cm, females mean 5.0cm (B142), male up to 8cm, female up to 5cm (B148).

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Coat / Pelage

Adult Female
  • Dorsal: reddish brown (russet to ginger brown).
  • Ventral: white to cream.

(B52, B142, B147, B148)

Variations (If present)
  • Winter: white (northern and eastern Eurasia), paler than summer otherwise.

Mustela nivalis vulgaris:

  • Irregular margin between dorsal and ventral colouration and may have distinct brown spot at corner of mouth, sometimes also brown spots on abdomen.

(B52, B142, B147, B148)

  • Two moults per year.
  • Timing controlled by daylength.
  • Spring moult: slow, starts head, progresses across back to abdomen.
  • Autumn moult: faster and in opposite direction.


New-born / Juvenile --

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Neonate (New-born) Characteristics

Blind at birth (B142, B148).

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Detailed Anatomy Notes
(Summary information provided for pertinent species-specific data cross-referenced in Wildpro)

  • Reproductive: 3-4 pairs nipples (only visible in adult female), testes in furred scrotum, smaller in winter. Simple uterus (B142).
  • Scent glands: anal glands (B142).

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Life Stages / Natural Diet / Physiology

Reproductive Stages

Breeding Season Mating February to August (B142).
Oestrus / Ovulation
  • Anoestrus September to February (B142).
  • Polyoestrus (B147).
Gestation / Pregnancy
  • 34-37 days.
  • No delayed implantation.

(B52, B142, B143)

  • 35-37 days (B147).
Parturition / Birth First litter April-May, second litter July-August (B143).
Neonatal development
  • Birth: blind.
  • 2-3 weeks: deciduous teeth erupt.
  • 3-4 weeks: weaned.
  • 4 weeks: eyes open (females before males).
  • 8 weeks: able to kill efficiently.
  • 9-12 weeks: family breaks up.
  • 12-16 weeks adult weight.

Slower growth in second litter.

(B142, B148)

Litter size
  • Usually 4-6, range 4-8 (B142).
  • 3-10 average 5 (B147).
  • 5-10 (B148).
  • 4-8 (B52).
Time between Litters / Litters per year
  • One or two litters per year (B142, B143, B148).
  • Possibly three in vole-plague years (B52).
Lactation / Milk Production
  • Up to12 weeks, although weaned 3-4 weeks (B142).
  • Weaned 24 days (B147).
Sexual Maturity
  • 3-4 months old - may mate in year of birth (B52, B142, B147).
  • Males fecund February to October in Britain (B142).
  • Mean life expectancy at independence less than one year (B142).
  • Rarely to three years in wild (B142).
  • Up to 10 years in captivity (B142).
  • 8-10 years (B148).

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Natural Diet

  • Mainly small rodents, e.g. bank voles and field voles, wood mice.
  • Rats taken more by males than females.
  • Young rabbits.
  • Also birds and bird eggs.
  • Avoid shrews generally (some individuals prefer these).
  • Require frequent meals (2-4g, 5-10 times daily) - cannot survive without food more than about 24 hours
  • Daily requirement about 1/3 body weight per day: Males 0.33g/g body weight per day, females 0.36g/g body weight/day.
  • Increase requirement in pregnancy (6-7% more) and lactation (80-100% more).

(B52, B142, B147)

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Detailed Physiology Notes
(Summary information provided for pertinent species-specific data cross-referenced in Wildpro)

Temperature 39-40C (B142).
Pulse Male 451 bpm (range 420-480 bpm), female 468bpm (range 420-510 bpm) (B142).
Respiration 96-104 breaths per minute (B142).
Faeces 36 long, thin (B142).
Haematology / Biochemistry --
Chromosomes 2n=42 (B142).
Other --

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Feeding Behaviour

  • Localised foraging in good areas.
  • Search through vole and mouse tunnels and runways, also mole runs.
  • Generally avoid rabbit burrows.
  • Locate prey by sight, sound, smell.
  • Kill by bite at back of neck.
  • Store food for winter.

(B142, B147)

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Parental Behaviour

Total rearing time nine weeks (B142).

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Social Behaviour / Territoriality

  • Solitary.
  • Separate territories for males and females.
  • Males have much larger territories (e.g. 7-15 hectares males, 1-4 hectares females (B147)
  • Variation in male territory size depending on food availability and season.
  • Male territory enlarges in spring.

(B52, B142, B143)

Inter-specific --

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Sexual Behaviour


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Predation in Wild

Wide range carnivorous mammals (foxes, cats, mink, stoats) and birds (hawks, owls).

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Activity Patterns

  • Active periods 10-45 minutes with rest periods.
  • 1-3 rest periods of four hours or more in each day.
  • Males more active in spring, females less active.
  • Climb well.
  • Swim well.


  • Active day and night.
  • Radio-tracking indicates more active in day.
  • In captivity more nocturnal.

(B52, B142)

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Habitat and Range

General Habitat Type

  • Wide range of habitats - fields, meadows, forests, mountains, riverbanks, lake shores, desert.
  • Requires shelter and food available.
  • Mainly where small mammals abundant.
  • Prefer woodland to open areas in winter in cold climates.
  • May spend whole winter under snow.
  • In open country stay in areas of cover - hedges etc.

(B142, B143, B148)

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Nests / Burrows / Shelters

  • Many nests in home range.
  • Take over nests of prey - do not construct own nests.
  • Also use resting places.


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Distribution and Movement (Migration etc.)

Normal Holarctic: northern North America (Alaska to north-eastern USA), western Europe to Eastern Siberia, Asia including Japan, northern Africa.
  • Further south into Mediterranean area, North Africa and Egypt than stoat.
  • Absent from Ireland.
  • Britain: mainland and offshore islands more than 380 square km (including Isle of Wight, Skye, Anglesey, Sheppey). Not found on islands where stoat not found.

(B142, B143)

Occasional and Accidental --

New Zealand (B51, B142, B143).

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Intraspecific variation

  • Mustela nivalis nivalis (Northern Scandinavia and Siberia) - White in winter, straight flank line.
  • Mustela nivalis vulgaris (Western Europe, including Britain) - Irregular flank line, brown all year.
  • Mustela nivalis boccamela Bechstein, 1800 sometimes recognised (Mediterranean).
  • Two subspecies in North America.
  • Mustela nivalis rixosa Least weasel in North America, sometimes considered separate species (B52).

(B142, B143)

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Conservation Status

Wild Population -

In Britain: native, common although may be declining. Pre-breeding population estimate of about 455,000, including 308,000 in England, 106,000 in Scotland, 36,000 in Wales. Population estimate was "based on a very limited amount of information for the species" although additional knowledge "may not necessarily have made a substantial difference to the estimate". (B221)

General Legislation
  • Bern Convention Appendix III (B143)
CITES listing --
Red-data book listing --
Threats Scarcity of prey and secondary poisoning may both possibly affect populations (B221).
Captive Populations  

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