Current status and future prospects of reptiles and frogs in Sydney's urban-impacted bushland reserves

Five large (greater than 35 ha) urban bushland reserves in Greater Sydney were selected where herpetofaunal assemblages could be deduced and there were recent herpetofauna surveys. Four reserves (Rockdale Wetlands Corridor, Wolli Creek Valley, Burnt Bridge Creek Corridor and Middle Harbour Bushland Reserves) had been surrounded by residential development for more than 50 years. The fifth (University of Western Sydney, Richmond campus) was surrounded by agricultural and peri-urban development. Records from the scientific literature, local natural history groups, amateur herpetologists and council archives were used to gather historic information on the frogs and reptiles. Interviews were also conducted with researchers and neighbours of the reserves. Eight extant species were common to all reserves while another, predicted to be in all reserves, was universally absent. Despite the relatively large size of these bushland remnants, in all reserves the number of reptile and frog species had declined since urbanisation. The largest losses occurred in the four urban reserves. Seven species predicted to have occurred historically were now only present in the peri-urban site. Some herpetofaunal groups were more vulnerable than others. Goannas were locally extinct in urban reserves. Tree frogs and geckos were depleted while ground frogs and skinks were reduced to approximately half their original species numbers. This is in contrast to the peri-urban site where there had been no loss of tree frogs or goannas and generally more than half of the species in each group were extant. Urban impacts that appeared to relate to herpetofauna decline were direct human intervention that resulted in death or removal of individuals (e.g. goannas, large snakes), interference with habitat such as bush rock removal (e.g. smaller snakes, geckoes, skinks), fire (e.g. non-burrowing small residents), interference with the water cycle including infilling and pollution (e.g. frogs) and exotic predators (e.g. dragons, turtles, skinks). In general, herpetofauna with the least future prospects were those most susceptible to decline. These included the large, conspicuous fauna that required a substantial home range, attracted the attention of humans because of ‘pet appeal’ or due to their perceived danger; were vulnerable at some stage of the lifecycle to predation by feral species; and had specific habitat requirements for reproduction such as quality water or open sandy banks for egg incubation. Those that are small, generalist and unappealing to humans are most likely to survive. There is, therefore, little doubt that diversity in reserves will continue to dwindle unless strategies are devised to overcome the present trend. Current conservation strategies that generally target single species need to be expanded to ecosystem level to monitor threats and management implemented for their removal.