The common weasel, little weasel, or simply weasel (Mustela nivalis), the smallest member of the weasel genus Mustela, native to Eurasia, North America, and North Africa.
marten
noun
Any carnivorous mammal of the genus Martes in the family Mustelidae.
How often have the words least weasel and marten occurred in a corpus of books? (source: Google Ngram Viewer )