Delayed Implantation in the Stoat (Mustela mustela)

Abstract

RECENT investigations have shown that the discontinuous type of embryological development first described in the roe deer^1,2 is less uncommon than was originally supposed³. In this and some other species the blastocyst is formed normally, but there is a period of several months during which it lies free in the uterine lumen before it becomes implanted. Both the European badger⁴ and the American badger⁵ show this type of delayed development, and recently it has been described in American weasels⁶ and martens⁷. According to Fischer⁴, unimplanted blastocysts are found in the European badger from the end of July until January, the young being born in March. Wright⁶ finds that in the long-tailed American weasel blastocysts lie dormant from July or August until about the following spring, the young being born in April. Watzka⁸ is said to have found a similar delay in implantation in the stoat.