Une femelle de Grand Murin Myotis myotis (Mammalia, Chiroptera) porteuse de deux embryons.

(Uploaded by Plazi for the Bat Literature Project) A dead ringed female Greater Mouse-eared bat Myotis myotis bearing twins was discovered in June 1990 in the South-western Switzerland, 4km away from the cave where it was tagged by July 1989. The bat was killed by a camivor, a domestic cat or a beech marten. The presence of a grey chin spot as well as undevelopped nipples at the date of the first tagging indicate that this female was born in 1988, and definitely primiparous in 1990. This is the first report of twins in this species. Since bat embryos are among the largest in mammals, relatively to mother body mass, and because M. myotis is essentially a ground gleaner, i.e. particularly vul­ nerable to terrestrial predators, it is argued that natural selection must strongly act against the production of twins in this specis.