Lizards and snakes have flourished in Australia over the past 20 million years as the continent has become more arid – and they reach a pinnacle in the Pilbara. Hot, geologically diverse and rocky, the Pilbara is well made for snakes and lizards. This region has the highest reptile diversity in Western Australia and is part of an Australian lizard hotspot running from central Australia to the Pilbara coast. More than 150 lizard and snake species (not counting sea snakes) have been recorded so far, and many are unique to the Pilbara. Geckos, skinks, goannas, dragons, blindsnakes and elapid snakes are particularly diverse.
A quarter to a third of the known geckos, skinks, and goannas in the Pilbara are unique to the bioregion – much higher than in other, similar-sized parts of the Australian arid zone – and other species are endemic to the rocky areas of the Pilbara and the adjacent Gascoyne bioregion. Endemism is particularly high in reptiles associated with rock. One conspicuous feature of many Pilbara lizards is their rich reddish colour matching the colour of ironstones.
The number of known species in the Pilbara has grown rapidly in the past 20 years as DNA studies have revealed much greater diversity than is evident judging by appearances alone. In 2007, for example, sliders (burrowing lizards) in the Pilbara previously regarded as one species, the wood mulch-slider (Lerista muelleri), were revealed as 6 species. Likewise, 7 new gecko species were revealed when Gehyra punctata was investigated, most endemic or near-endemic to the Pilbara. There is likely to be much more hidden diversity in the Pilbara reptiles.
Other Pilbara reptiles include the flat-shelled turtle (Chelodina steindachneri), the saltwater crocodile (sighted occasionally on the coast) and 3 threatened marine turtles – the flatback, green and hawksbill – that nest on Pilbara islands and also occasionally on the mainland (but only flatbacks and greens). All 3 species are threatened. Little is known about the ecology of marine turtles in the Pilbara and most potential habitat has not been confirmed. The hawksbill rookery on Rosemary Island in the Dampier Archipelago is the largest known in the Indian Ocean and one of the largest – ‘if not the largest’ – in the world. It has been monitored by volunteers (managed by Parks and Wildlife) since 1986. Recent aerial surveys have revealed substantial turtle activity on many other islands, indicating that the Dampier Archipelago is likely to be of global importance for marine turtles.
The Pilbara also hosts 13 frog species: 3 are endemic or near-endemic to the Pilbara, 4 are widespread aridzone species, and 4 are tropical, linked to Kimberley populations by a thin strip of coastal shrubland.
No reptiles or frogs are known to have gone extinct in the Pilbara. Fifteen reptiles are listed as threatened or priority species in Western Australia, 6 are listed nationally as threatened and 5 are listed internationally. The endangered Nevin’s slider (Lerista nevinae) is particularly vulnerable because it occurs in only a few thousand hectares in coastal sands habitat often close to major industrial development. It is the Pilbara reptile ‘most likely to face significant habitat reduction and population size in the next 20 to 50 years’.