We have heard the suggestion many times that there are two varieties
of the common weasel, but think this is not the case. The mistake no
doubt arises from the marked difference in size between the males and
females; the dog weasel is twice or sometimes three times the size of
its sister, and is nearly as big as a small female stoat, while the dog
weasel's sister may be hardly larger than a big mouse. Then the changes
in the weasel's coat are deceptive. In spring a rusty red fur takes
the place of the soft winter brown of the upper parts, while the white
under-parts turn to a yellow tone. The ordinary brown of rats also
changes to a striking rusty red shade in spring. This is most obvious
in the case of rats living in burrows in soil, and often going short
of food, and the rusty fur is specially marked on rats that have been
feeding on carrion sheep and lambs. Shortness of food has the effect of
prolonging the business of coat-changing, as is well seen in the case
of a ferret kept on short commons. A white ferret is deep yellow in
the spring before it has changed its coat. Stoats, too, show yellow on
parts which will be white in the new coat.
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