A note on the Australian freshwater crocodiles inhabiting Tunnel Creek cave, West Kimberley

WA Museum Records and Supplements | Updated 7 years ago

INTRODUCTION – Tunnel Creek National Park, located 390 km east of Broome in the Kimberley region of Western Australia, is one of region’s top tourist attractions. The 91 ha national park is positioned within the Napier Range which is composed of limestone, remnants of a Devonian barrier reef system formed around 350 million years ago (Goudie et al. 1990). The park contains a limestone cave system ~750 m in length (cave entrance at 51K 727683 8051871) (Figure 1). It is considered to be one of the oldest cave systems in Western Australia and also a nationally important wetland (Environment Australia 2001). The cave also has historical value as the Aboriginal freedom fi ghter Jandamarra, a member of the Bunuba group of the area, evaded the police and others for nearly three years using it as a hideout, until he was shot in April 1897 at the cave entrance (Pedersen and Woorunmurra 1995).

The cave is up to 20 m high and up to 20 m wide and contains permanent pools of freshwater throughout the year. Tunnel Creek generally fl ows during 4–5 months of the year (December to April), during which it is connected to a permanent, large freshwater pool located, ~15 m outside the southern entrance of the cave (Figures 1, 2A). Nearly halfway in, the roof of the cave has collapsed allowing sunlight to reach the banks of the cave in a ~30 m section. Other than this, sunlight does not penetrate the remainder of the cave, beyond the entrances. Two springs with warmer water, possibly created as a result of a perched water table passing through heated rocks outside the cave, fl ows into the cave creating ~1 m and ~2 m high waterfalls (Figure 1). Water within these two pools is warmer than the other pools within the cave.

While no detailed studies on the herpetofauna of the area have yet taken place, anecdotal information states the occasional presence of Australian freshwater crocodiles (Crocodylus johnstoni) inside the cave (Gueho 2003; Laurie 2010). Confirmed records of crocodilians inhabiting large caves are very rare and limited to a population each of the dwarf crocodile (Osteolaemus sp.) and the Nile crocodile (C. niloticus) (Handwerk 2003; IRD 2012). Hence in this short note, we provide more robust observational records of the population of C. johnstoni inhabiting the Tunnel Creek cave and discuss likely reasons for their occupation of the cave.