Aspects of the population ecology of the Green and golden bell frog Litoria aurea at the northern end of its range

Development of appropriate conservation programs for threatened species requires a basic understanding of their population ecology. We studied a population of the Green and golden bell frog Litoria aurea in the far north of its range. This population occupies a coastal lagoon within Yuraygir National Park. Permanent tagging of frogs was conducted between August 1998 and March 2003. Population estimation based on the mark and recapture of frogs in 1998-99 suggested that the population contained at least 100 adult male frogs. Approximately 75 male bell frogs called from around the lagoon on one night in November 2001. The number of females captured in any year was low and it is unclear whether this is due to low detectability associated with irregular use of breeding sites or a highly skewed sex ratio. More than 60% of tagged male frogs were recaptured across one active season, but only two were recaptured outside the season of initial capture. This suggests that few male frogs live longer than about 2 years as adults. Breeding was erratic over a 6-year period and only one major metamorphosis event was observed. It appears that bell frogs may have greater breeding success in ephemeral ponds forming away from the lagoon, though there is a risk that these ponds may not persist for tadpoles to complete development. Frogs in this northern population were predominantly brown in colour, suggesting some morphological and genetic differentiation from southern populations in which most frogs are predominantly green. Further study of this important population is needed to more adequately determine the size of the female component of the population, and to better understand the limits on successful breeding. These issues will influence our understanding of the viability of the population, and therefore our ability to devise appropriate management actions. This study provides the first published account of aspects of the population ecology of the Green and golden bell frog in relatively undisturbed natural habitat.