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RESEARCH ARTICLE
Contents Vol 32(4)

Population parameters and life-table analysis of two coexisting freshwater turtles: are the Bellinger River turtle populations threatened?

Sean J. Blamires A D , Ricky-John Spencer A B , Peter King C and Michael B. Thompson A
+ Author Affiliations
- Author Affiliations

A Heydon-Laurence Building A08, Biological Sciences, University of Sydney, NSW 2006, Australia.

B Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA 50011, USA.

C Department of Biology, Francis Marion University, PO Box 100547, Florence, SC 29501-0547, USA.

D Corresponding author. Email: sbla3978@mail.usyd.edu.au

Wildlife Research 32(4) 339-347 https://doi.org/10.1071/WR04083
Submitted: 20 September 2004  Accepted: 24 May 2005   Published: 5 July 2005

Abstract

Two species of freshwater turtle coexist in the Bellinger River: Elseya georgesi is common but limited to the Bellinger River, whereas Emydura macquarii is widespread but rare in the Bellinger River. The Bellinger River population of E. macquarii has been proposed as a distinct subspecies, so it may be endangered. Survivorship, fecundity, growth, size and age were determined for El. georgesi and the finite rate of increase (λ) was estimated by a life-table analysis using mark–recapture data from surveys between 1988 and 2004. These parameters were compared with those of well studied populations of E. macquarii to assess whether modelling the demographic parameters of El. georgesi could serve as a surrogate for estimating the influences of these demographic parameters on λ in the Bellinger River population of E. macquarii. We estimated that ~4500 El. georgesi inhabit the study area and, despite a size distribution strongly biased towards large individuals, the population is increasing (λ = 1.15) in the best-case scenario, or slightly decreasing (λ = 0.96) in the worst-case scenario. Comparing El. georgesi with E. macquarii from the Bellinger River and elsewhere suggests that E. macquarii grows faster, attains greater maximum size, has a greater clutch size and a higher fecundity than El. georgesi. Hence, El. georgesi does not serve as a good surrogate to determine demographic influences on λ in E. macquarii.


Acknowledgments

Research was funded by an ARC Linkage Grant and the National Parks and Wildlife Service through the Fox Threat Abatement Plan and Bellinger River Catchment Grant. Turtles were captured under NSW National Parks and Wildlife Service licence numbers S10957 and B1313, and University of Sydney Animal Ethics clearance numbers L04/12-2003/3/3843 and L04/12-94/2017 and NSW Fisheries licence number F86/2050. T. Landklide, D. Warner, J. Goudkamp, J. Herbert, and F. Seebacher provided valuable feedback on a draft of the paper. J. Cann provided miscellaneous feedback on the Bellinger River and its turtles. M. Murphy (NSW NPWS, Coffs Harbour) was responsible for instigating the study in 2000 and T. Scanlon and B. Nesbitt (NSW NPWS, Dorrigo) organised logistics and accommodation for 2000–04. We thank A. and A. Hickey, D. and P. Browning, N. and J. Ralph, L. Lemke, P. Kinmon, S. Eyre, J. Kramer, P. Krug, Thora Poll Herefords, Dreamtime, Kandahar, and Homelands Communities and Orama Public School for access to specific sites. The assistance of M. Murphy, G. McDonald, S. Hull, A. Ried, C. Browne, J. Sparrow, M. Blamires, D. Booth, F. Seebacher, D. Lim, T. Scanlon, A. Harber, T. Prior, and local volunteers was appreciated.


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