Messy habitat helps city frogs

University of Melbourne, Science Alert 12 Mar 10;

A new study has revealed that lizard, snake and frog populations in Melbourne have declined dramatically since human settlement, and in order to conserve our reptiles and amphibians it is the quality, and not just the quantity of habitat that will help maintain biodiversity in our cities.

The findings coincide with the UN's year of biodiversity in 2010, with lead author Dr Andrew Hamer, based at the University of Melbourne, stressing that reptile and frog habitats need be conserved in residential areas by keeping them as natural as possible, even if they are only small areas.

The study analyzed Melbourne's lizard and frog populations from Victorian Government databases, extending almost as far back as European settlement. The work was undertaken by Dr Andrew Hamer and Assoc Prof Mark McDonnell from the Australian Research Centre for Urban Ecology (ARCUE) based at the Royal Botanic Gardens Melbourne and School of Botany, University of Melbourne.

They predicted which species would survive in the greater Melbourne metropolitan area, in order to identify those most sensitive to the creation of urban infrastructure and increases in human population size (urbanization), and therefore potentially at greater risk from future development.

They found that throughout greater Melbourne (up to a 60km radius from the city centre), 81 per cent of the frog species observed in 1850 had a high probability (greater than or equal to 95 per cent) of surviving until 2006. However, only 56 per cent of the reptile species had a high probability of survival. The year 2006 was chosen as the last entry in databases, but researchers note that the trends would be applicable in 2010, if not worse.

Within 10km of Melbourne, populations of reptiles declined further with only 46 per cent of species examined having a high probability of surviving, with frogs doing much better at 86 per cent of species surviving. For example, 53 per cent of skink species have a low probability of surviving because they require natural habitats such as native grassland and rock outcrops.

"Our research suggests that many reptile and frog species have been negatively affected by urbanization,” says Dr Hamer.

“It is essential to keep some native remnant areas which are as structurally complex as possible. This allows small mammals, frogs, lizards and snakes access to fallen logs and vegetation that they need to complete their daily and seasonal activities such as basking, foraging, predator avoidance and nesting.”

Assoc Prof McDonnell notes that large lizards and snakes may be more severely impacted as they require larger areas, encountering road traffic or houses where they may be killed by people or their pets.

“Implementation of the recommendations of the recently published government white paper entitled ‘Securing Our Natural Future’ would assist in slowing the further loss of reptile and frog species. To effectively conserve reptiles and frogs in cities and towns we need to protect remaining habitats and link them with corridors of native vegetation.”