Expanding Melbourne city puts bite on reptiles

Bridie Smith, The Age 10 Mar 10;

THE largest study of its kind to reveal how Melbourne's frogs, lizards and snakes have fared after European settlement has identified species that are most susceptible to urbanisation, and therefore most threatened by development.

Coinciding with the UN's International Year of Biodiversity, Melbourne University analysis of data dating to the 1800s has found many of the 16 frog species and 39 reptile species studied have been pushed to the urban fringes as bushland becomes bitumen.

Among them is the brown toadlet, which once called the south-eastern suburbs home, but no longer exists in Melbourne, having been pushed out to north of the Great Dividing Range.

Like many species, its disappearance from greater Melbourne is largely due to habitat loss. According to the study, just 1.66 per cent of the land within 10 kilometres of the city is still covered by remnant vegetation, while outer-suburban areas have retained nearly 16 per cent coverage.

"It is essential to keep some native remnant areas which are as structurally complex as possible," said Andrew Hamer, research associate at Melbourne University's botany department.

But despite what popular opinion might suggest, urban life has benefited some species.

Tree frogs, such as the southern brown tree frog, which inhabits a lot of the ornamental ponds in the city's gardens, have adapted to the urban environment - their ability to climb giving them access to steep-sided pools and ponds.

The results of the study by Dr Hamer and Mark McDonnell, to be published in Austral Ecology, found these tales of triumph over adversity were rare. Overall, Melbourne's lizard, snake and frog populations have declined dramatically since European settlement.

The proliferation of paved areas has done little for the common spadefoot toad, which likes to burrow into soil and sand. Roads, traffic, buildings and fences also block the path of species that like to travel to feed and breed - making the threatened growling grass frog and tree goanna particularly sensitive to urban development.

Dr Hamer, lead author of the paper, said reptiles had been hit hardest.

"We really need to keep an eye on some of these reptiles, especially the smaller ones like skinks which require specialised habitat with rocky outcrops or native grassland," he said.

White's skink, which has weathered a shrinking habitat, has not proved an urban adaptor. Similarly, species such as the grassland earless dragon and striped legless lizard, which called grassland environments home, have had to move out as developers move in.

Among the few reptile "urban survivors" are the delicate skink, the garden skink and the blue-tongued lizard.

After being settled by Europeans in 1835, greater Melbourne by 1960 covered 97,851 hectares and by the 1990s this had swelled to more than 202,600 hectares, according to the paper. The greater Melbourne area now covers 393,000 hectares.