South Coast Froglet - Crinia subinsignifera
Usually a very dark colored small frog, which is extremely difficult to separate from some forms of the Bleating Froglet, Crinia pseudinsignifera that are of similar size (around 25 mm in length). To further complicate identification, it too often co-inhabits low-lying areas in the Esperance region that are subject to winter flooding.
Besides their calls which are quite different, the easiest way I have found to visually tell them apart is by the coloration of their belly. The South Coast Froglet has a largely dark grey or brown belly with relatively little white, but plenty of dark brown, grey, black and white flecks. The Bleating Froglet on the other hand has a largely white belly with relatively few black or dark grey flecks, although breeding males have a dark grey bottom jaw. Their distinctive call can be heard here: http://frogsaustralia.net.au/frogs/display.cfm?frog_id=16
