It can live in almost any ground habitat where necessary cover can be found: forests, hedges, high grass, undergrowth, swamp, precipices, moors, marshes and mountain screes. Its back is reddish-brown, its stomach white and the tip of its tail black; in winter it turns completely white apart from the tip of its tail which remains black. It is 24-29 cm long, plus a 8-12 cm tail, with a weight of 125-450 g.
The prey of the ermine is made up mainly of rodents up to the size of rats, shrews, bank voles and sometimes even hares, as well as eggs, birds, reptiles, amphibians and insects. It generally ignores vegetation.