The importance of habitat design and aquatic connectivity in amphibian use of urban stormwater retention ponds

Stormwater retention ponds in urbanizing catchments are constructed to collect and treat runoff from impervious surfaces. Amphibians often inhabit retention ponds, which may partly offset the loss of natural wetlands resulting from urbanization. We investigated the use of retention ponds by frogs in a rapidly-urbanizing region of south-eastern Australia to (1) determine the habitat attributes associated with individual species, and (2) recommend specific wetland design criteria to enhance populations of frog species in the region and in other urbanizing areas throughout their distribution. We detected nine species of frogs during calling surveys at 30 retention pond sites in Greater Melbourne, 2008-2010. There were contrasting differences in habitat associations among five species for which we produced regression models of abundance or occurrence. The mean abundance of Crinia signifera increased with site area, whereas Limnodynastes dumerilii was associated with smaller sites. The occurrence of L. dumerilii was positively associated with waterbody shore depth, whereas L. peronii and L. tasmaniensis were associated with shallow shores. Two species were positively associated with time since construction or since dredging of a site, whereas the occurrence of L. dumerilii decreased with site age. Aquatic vegetation at a site was important for the occurrence of L. peronii and Litoria ewingii. There was evidence for a positive effect of aquatic connectivity on the occurrence of Limnodynastes peronii, which emphasizes the importance of riparian corridors in urban settings. These results highlight the contrasting differences in habitat associations among species in the region. We recommend that retention ponds in our region and elsewhere be constructed or enhanced to include specific habitat attributes that were found to be associated with different amphibian species. We recommend long-term monitoring at sites to determine whether retention ponds augment existing frog populations or contribute to declines.