Hattah-Kulkyne Ramsar Wetlands Protection Project: can fox control reduce predation of freshwater turtle nests? A. Robley, K. Howard, L. Woodford, A. Taglierini, and M. Thompson August 2017 Arthur Rylah Institute for Environmental Research Unpublished Client Report for the Mallee Catchment Management Authority Hattah-Kulkyne fox control and turtle nest survival Arthur Rylah Institute for Environmental Research Client Report Hattah-Kulkyne fox control and turtle nest survival Hattah-Kulkyne Ramsar Protection Project: can fox control reduce predation of freshwater turtle nests? Alan Robley1, Katie Howard1, Luke Woodford1, Angelo Taglierini2, and Malcolm Thompson2 1Arthur Rylah Institute for Environmental Research 123 Brown Street, Heidelberg, Victoria 3084 2Mallee Catchment Management Authority, PO Box 5017, Mildura, Vic 3502 August 2017 In partnership with and Arthur Rylah Institute for Environmental Research Department of Environment, Land, Water and Planning Heidelberg, Victoria Hattah-Kulkyne fox control and turtle nest survival Report produced by: Arthur Rylah Institute for Environmental Research Department of Environment, Land, Water and Planning PO Box 137 Heidelberg, Victoria 3084 Phone (03) 9450 8600 Website: www.delwp.vic.gov.au Citation: Robley, A., Howard, K., Woodford, L., Taglierini, A., and Thompson, M. (2017). Hattah-Kulkyne Ramsar Protection Project: can fox control reduce predation of freshwater turtle nests? Unpublished Client Report for the Mallee Catchment Management Authority. Arthur Rylah Institute for Environmental Research, Department of Environment, Land, Water and Planning, Heidelberg, Victoria. Front cover photo: Lake Konardin and Red Fox (Vulpes vulpes) (Alan Robley); turtle nest monitoring (Malcolm Thompson). © The State of Victoria Department of Environment, Land, Water and Planning 2017 This work is licensed under a Creative Commons Attribution 3.0 Australia licence. You are free to re-use the work under that licence, on the condition that you credit the State of Victoria as author. The licence does not apply to any images, photographs or branding, including the Victorian Coat of Arms, the Victorian Government logo, the Department of Environment, Land, Water and Planning logo and the Arthur Rylah Institute logo. 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Arthur Rylah Institute for Environmental Research Client Report Hattah-Kulkyne fox control and turtle nest monitoring Contents Acknowledgements 8 Summary 9 1 Introduction 11 2 Methodology 13 2.1 Study site 13 2.2 Fox control 14 2.3 Monitoring foxes 14 2.4 Changes in fox abundance 15 2.5 Monitoring changes in artificial nest predation rates 15 3 Results 17 3.1 Changes in fox abundances 17 3.1.1 Poison baiting operation 17 3.1.2 Fox naïve occupancy and camera activity 19 3.2 Nest predation rates on artificial Eastern Long-necked Turtle nests 20 4 Discussion 21 Management implications 22 References 24 Appendices 27 8 Hattah-Kulkyne fox control and turtle nest monitoring Acknowledgements This project was commissioned by the Mallee Catchment Management Authority and funded by the Australian Federal Government. We would like to thank Louise Chapman, David Scammell, Malcolm Thompson and Nicole Wishart (MCMA) for assistance and support during the project. Parks Victoria, including Shane Southon, Bradd Boldock, Rhet Cameron, Mick Peterson and Parks Victoria staff at the Hattah-Kulkyne office and depot for support with logistics, access to, and use of the depot facilities and information about Hattah-Kulkyne National Park. Paul Moloney (Department of Environment, Land, Water and Planning) for support and assistance with this project. Comments from David Bryant and Lindy Lumsden improved this report. Arthur Rylah Institute for Environmental Research Client Report Hattah-Kulkyne fox control and turtle nest monitoring 9 Summary Reducing predation by introduced predators on seasonally vulnerable prey such as nesting reptiles and bird species is of interest to biodiversity managers and around the world. In Australia, the Red Fox (‘fox’, Vulpes vulpes) is a significant predator of freshwater turtle nests, destroying up to 93-100% of nests. This project builds on previous work commissioned by the Mallee CMA (Robley et al. 2016a, 2016b) and studies by K. Howard (unpubl. data) and Spencer (2002, 2005) and is aimed at increasing our understanding the impacts of fox predation on freshwater turtle nest survival and strategies to mitigate that impact at the Hattah-Kulkyne National Park (HKNP) Lakes system. In 2016-17 we implemented a non-randomised BACI intervention study to assess the effectiveness of a short-term (12-week) targeted baiting operation to reduce the level of nest predation on artificial turtle nests around the Hattah–Kulkyne Lakes system. We assessed changes in the fox population via two independent indices of activity (free feed bait take, camera activity and estimates of naïve occupancy). We used artificial turtle nests to assess changes in predation rates before and in the last weeks of the fox control operation at two lakes subject to fox control and one lake with no fox control activities. Overall, 431 poison baits were removed from the 181 bait stations during the course of the baiting operation, with 87% of bait stations having at least one bait removed during the course of the program. The proportion of baits taken per week was significantly lower at the end of the baiting period (0.29, CL 0.22 – 0.38) compared to the beginning of the program (0.09, CL 0.05-0.13). Unexpectedly, the proportion of weekly free feed bait increased following the fox control operation in both the fox control area and the non-fox control area. Also unexpectedly, activity (the number of independent images over a 24-hour period) increased in the fox control area from 1.4 (CL 0.79-2.27) to 2.1 (CL 1.26-3.34) but decreased in the non-fox control areas from 3.7 (CL 2.47-5.35) to 2.3 (CL 1.54-3.53). Estimates of naïve fox occupancy (the number of sites where foxes were detected/total number of sites) increased in the fox control area from 0.29 pre-control to 0.63 post-control. While in the non-fox control area estimates remained similar; 0.72 and 0.66 respectively. The rate of artificial nest survival when combined across Lakes Mournpall and Konardin was not significantly different in the final weeks of control compared to the pre-control rates (45% and 51% respectively). However, there was a significant difference in survival rates between the lakes. At Lake Mournpall survival rates increased from 28% to 64%, while at Lake Konardin they decreased from 75% to 38%. In contrast, at Lake Kramen (no fox control), survival rates went from 48% to just 5%. Results suggest that, (a) the fox control operation may have prevented a significant reduction in predation rates of turtle nests at Lakes Mournpall and Konardin, and (b) that reducing the impact of fox predation on freshwater turtle nests can vary in space and time (previous studies at these sites produced different results, see Robley et al. 2016a and 2016b) and that possibly operational limitations, environmental conditions and individual site factors may play a significant role in determining the success of fox control and the level of nest predation at any given lake system. It has been suggested that nest survival rates need to be greater than 50% once in every 3-5 years for Eastern-Long-necked Turtle populations to persist (R. Spencer unpubl. data) with turtle nesting coinciding with rainfall events (leading to flood plain inundation). The environmental watering plan for the Hattah Lakes system is for a minor flood event every three in 10 years and a major flood eight in every 10 years (Murray-Darling Basin Authority 2012). Hence, it may be possible to match fox control to when the environmental conditions are best suited to turtle nesting, and maintaining survival rates above 50%. These conditions would include; • Predicted or known periods of natural and planned flooding leading into the turtle nesting season. • When the previous autumn and winter rainfall and temperatures have been moderate, promoting primary production and leading to increased reproductive output and survival for foxes. 10 Hattah-Kulkyne fox control and turtle nest monitoring As recommended in previous reports, increasing the intensity of the baiting operation around the immediate area of nest locations and using a more target specific bait is likely to be more effective at protecting turtle nests. Increasing our understanding of the way foxes use the lake habitat and how this changes with underlying food resources would improve our ability to target fox control operations. Also, increased knowledge of the level of recruitment required to ensure turtle populations survive would benefit management. While effective short-term predator control for protecting seasonally vulnerable prey is desirable and achievable, the practical implementation of such control can be a significant impost on land managers, requiring a substantial commitment in time and resources in order to ensure control strategies are delivered. Staggering this effort to coincide with peak fox predation pressure and turtle recruitment maybe a strategy that is affordable and could meet the objective of protecting vulnerable Eastern Long-necked Turtles at HKNP.