Eesti Post issued a stamp depicting weasel (Mustelanivalis), a representative of Estonian fauna.
The tail of the weasel, brownish on the back and white on the belly in the summer, is slightly shorter than that of the other small carnivore, the ermine, and the hair at the end of its tail is never black. In the winter, the weasel turns white all over. Weasels live everywhere where they can hide and where there is prey, from sand dunes to grasslands to forests and hills. They are active round the clock. The tracks mostly come in pairs, and the track of the tail is noticeably only seldom. The weasel likes to sometimes stand up and observe the neighbourhood. When disturbed it hisses or trills at a high pitch. It expresses fear by means of sharp yelping. The weasel is so small (body length 15 to 20 cm) that it can follow rodents into their nests. It mainly catches and eats microta and mice, but does not refuse birds and eggs either. In order not to die it has to eat at least every 24 hours. Sometimes it takes over its the barrow of its prey. When disturbed it hisses at a high trill and expresses fear by means of short sharp yelps.
Gestation lasts from 34 to 37 days, and the litter usually has four to six young. There could be two litters in one year. The female takes care of the young. In nature it lives three years old, but in artificial conditions it can live up to ten years. It is common everywhere in Estonia, even on small islands.