Short-tailed bats (Mystacina sp.) were rediscovered in Nothofagus dominant rainforest in the Eglinton Valley in February 1997, representing the first records of these bats in Fiordland since 1871. Breeding females, adult males and juveniles were captured. This paper presents preliminary observations of taxonomy, echolocation calls, population size, habitat use, activity patterns, home range size, movements, roosting, and singing behaviour. Compared to lesser short- tailed bats (M.