Population monitoring of the vulnerable wallum sedge frog (Litoria olongburensis) in north-eastern New South Wales

The literature on the population ecology of Australian frogs provides relatively few accounts of population monitoring. This has hampered our ability to understand how frog populations respond to dynamic rainfall patterns and to determine the stability of populations of threatened frog species. We conducted biannual monitoring of the wallum sedge frog (Litoria olongburensis) along transects at 10 sites over a 4-year period (1996-2000). We recorded six environmental parameters to assess their influence on our population indices. Monitoring of transects indicated that populations were rarely stable and fluctuated from year to year. Counts of adults were negatively influenced by rain during the previous day but positively influenced by rain during the previous week. This suggests that timing of recent rainfall has a differing influence on habitat use by adult frogs. Counts of adults were also significantly influenced by site and census period. Numbers of juveniles were influenced by rain during the previous three months, which may suggest that successful recruitment depends on higher water levels in the sedge swamps. Counts of juveniles were also significantly influenced by census period. Our analysis reveals that, after controlling for the influence of rainfall, the number of adult frogs per census varied between 10 and 20 per transect. The number of juveniles varied between 5 and 15 per transect per census. We conclude that the wallum sedge frog across the geographic range of our sites was not in decline during our monitoring period. In light of our findings we provide a review on population monitoring of Australian frogs. © CSIRO 2005.