THE ANIMAL FILES

Least weasel

Mustela nivalis

A slender body follows prey into its own tunnels.

Least weasels hunt small rodents using a long flexible body and short limbs. Northern populations can change to a white winter coat, while other populations retain different seasonal appearances. Abandoned burrows provide sleeping, nursery and food-storage space.[1]

Follow the evidence ↓
Least weasel
Image: Keven Law · Commons · CC BY-SA 2.0
Following narrow passages
The body is long and flexible.[1]
Seasonal coats
Winter whitening occurs in northern and high-altitude populations.[1]
Borrowed burrows
Abandoned rodent burrows become dens.[1]

Following narrow passages

The head is no thicker than the neck, with short legs beneath an elongated, flexible trunk. This narrow shape lets the weasel follow rodents through their tunnels.[1]

Seasonal coats

Summer upperparts vary from brown to sandy shades above pale underparts. Northern and high-altitude animals can turn white in winter, but the change is not a universal feature across the range. The tail lacks the conspicuous black tip associated with stoats.[1]

Borrowed burrows

The weasel uses abandoned burrows and lines a nest chamber with straw and prey skins. Chambers serve resting, rearing kits and storing food. Local rodent abundance also influences feeding opportunities, with birds or young rabbits contributing in some circumstances.[1]

A COMMON MIX-UP

Do all least weasels turn white every winter?

No. Winter whitening is geographically variable rather than universal.[1]

TRY A LITTLE REASONING

Why would a narrow head and flexible trunk help a rodent hunter?

Reveal the explanation

They allow pursuit inside narrow burrows where broader animals cannot move as easily.[1]

Sources & editorial notes

Adapted and translated from the cited Wikipedia revisions, with source-linked reasoning. Image credit and licence are listed separately above.

Adapted and translated from Wikipedia contributors; exact revisions are linked below. CC BY-SA 4.0

  1. Wikipedia contributors — Least weasel (cited revision)
  2. NCBI Taxonomy — Mustela nivalis

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