Population estimation of the Green and golden bell frogLitoria aureaat Port Kembla

Abstract

Estimates of population size are fundamental to the development of effective management of threatened species. We conducted a tagging study of a population of the endangered Green and Golden Bell Frog Litoria aurea at Port Kembla, on the New South Wales south coast. Over 200 adult frogs were tagged across three breeding sites between November 1998 and January 2000. Population estimation based on the mark and recapture of frogs in 1999-00 suggested that the two larger breeding sites together contain >300 adult frogs.Although these sites were only 500 m apart, no tagged frogs were recorded to move between them. In contrast, one female bell frog moved 1.25 km between one of these and the third site over a 14 month-period.The ratio of male to female frogs was 2.5: 1, suggesting either that the population is male-dominated or that females are more cryptic in their behaviour than males and use habitat differently. Based on this ratio the sites contained at least 85 adult females in 1999-2000. Only 13 frogs were recaptured outside the season of initial capture.The longest interval between captures was 14- 16 months, for three of these frogs. This suggests that few frogs live longer than about 2 years as adults. Given that a small number of other breeding sites occur in Port Kembla, the total population size is estimated to exceed 400 adult frogs. Further study of this important population is needed to refine these estimates of population size and to confirm population stability.