Life history of an endangered amphibian challenges the declining species paradigm
Andrew J. Hamer A B and Michael J. Mahony AA Discipline of Biological Sciences, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia.
B Corresponding author. Email: ahamer@ecologypartners.com.au
Australian Journal of Zoology 55(2) 79-88 https://doi.org/10.1071/ZO06093
Submitted: 5 November 2006 Accepted: 27 March 2007 Published: 28 May 2007
Abstract
Declining species of vertebrates, including amphibians, have a life history that is characterised by low fecundity, long time to maturity, limited capacity to disperse and habitat specialisation. However, by studying aspects of the life history of an endangered amphibian in south-eastern Australia we show that a paradox may exist for some declining amphibians. We used standard mark–recapture methods over two breeding seasons (2000–01) to study a population of the green and golden bell frog (Litoria aurea) on Kooragang Island, New South Wales, with the aim of determining its age structure, and the growth and survival rates of individuals. Two age classes for males and three for females were derived using von Bertalanffy growth models. Around a quarter of the male and female marked population was a first-year cohort. The male and female age structures appeared to be stable over the two breeding seasons. However, there were fewer female L. aurea in the <12-month age class and more in the >24-month age class in 2001, which may indicate that recruitment declined in the study area. A short time to maturity (~3 months) was recorded for males. The maximum-likelihood estimate of survival for males in the 2000 breeding season was relatively high (0.76), although the capture probability was low (0.19). The biology of L. aurea conforms to an ‘r’-strategist, which is characteristic of a colonising or ‘weed-like’ species and not of one that has become extinct over much of its former range.
Acknowledgements
This work was funded by Port Waratah Coal Services through the Hunter Catchment Management Trust. We thank Rod Wright for assistance with fieldwork. We thank Dale Roberts, Simon Lane and two anonymous reviewers for comments on the draft manuscript. Geoff Mason (Broken Hill Pty Ltd) kindly provided access to industrial land. Permission for animal use in the field studies was given by the Animal Care and Ethics Committee, University of Newcastle (Approval No. 678 1000-2, Department of Agriculture, New South Wales), and New South Wales National Parks and Wildlife Service (Licence No. A2650).
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