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Arthur Rylah Institute for Environmental Research Unpublished Client Report for the Mallee Catchment Management Authority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, 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 Unpublished Client Report for the Mallee Catchment Management Authority.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

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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.

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Hattah-Kulkyne fox control and turtle nest monitoring 9

Summary

Reducing predation by introduced predators on seasonally vulnerable prey such as nesting and 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.

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Hattah-Kulkyne fox control and turtle nest monitoring 11

1 Introduction

Introduced into Australia in 1871 (Saunders et al. 1995), the Red Fox (‘fox’, Vulpes vulpes) is now widespread and common across the continent, and it has been implicated as the main factor in the complete or regional extinction of a range of critical weight range (35–5500 g average body weight) native mammals (Burbidge and McKenzie 1989; Short and Smith 1994) and small reptiles (Olsson et al. 2005). There is increasing evidence that longer-term fox control strategies are effective for protection or recovery of native species (Kinnear et al. 2002; Saunders et al. 2008; Fletcher et al. 2010; Robley et al. 2014). The cost of long-term control programs can be significant, so they are hard to maintain when there are changes in funding priorities (Reddiex and Forsyth 2006). In contrast, short-term control programs cost less, can reduce fox abundance quickly (Thompson and Fleming 1994), and for prey species that are vulnerable for short periods, they may be sufficient to allow an increase in abundance and productivity (e.g. Tapper et al. 1996; Harding et al. 2001). However, Côté and Sutherland (1997) reviewed 20 published studies in a meta- analysis on the effectiveness of removing predators to protect bird populations. They cite several examples in which short-term removal benefited nesting success, but long-term growth in prey populations was not evident because these gains were lost as soon as predator control ceased. It remains unclear which strategy is most effective at providing relief from predation pressure for seasonally vulnerable prey. Freshwater turtles nest seasonally, and in temperate parts of Australia, Eastern Long-necked Turtles (Chelodina longicollis) nest from late spring to early summer (Goode and Russell 1968). This coincides with the time of year when female foxes have high energy demands (are weaning young) and newly independent young foxes are emerging (Saunders et al. 1995; McIlroy et al. 2001). In south-eastern Australia, foxes have been recorded destroying up to 93% of turtle nests along the (Thompson 1983) and can destroy up to 100% of nests along the mid-Murray (K. Howard unpubl. data). Thompson (1983) found that a disproportionately lower number of juvenile turtles were recruited into populations where fox abundances were high, leading to adult-biased populations. Thompson (1983) concluded that populations of these long-lived species (20–40 years) are in decline due to nest predation, with declines likely to be exacerbated when ageing adults die. In addition, foxes kill nesting female turtles, lowering adult survivorship, which may lead to population declines if there is no density-dependent compensation in adult survivorship (Spencer and Thompson 2005). Artificial nests have been used widely in the study of predation impacts on both avian (Berry and Lill 2003) and turtle species (Marchand et al. 2002; Spencer 2002; Dawson et al. 2014), and have the advantage of allowing control over sample size and the type, duration, timing and treatment of nests, while controlling for confounding effects. In a study in south-eastern Australia, Spencer (2002) showed that predation rates on artificial turtle nests were comparable with predation rates on natural turtle nests. Natural flooding of the Hattah Lakes in north-western Victoria has been disrupted for the past 100 years due to river flows being diverted for agriculture, industry and town water supply, resulting in infrequent flooding events and a substantial loss of ecological value in the lake system. A program to reinstate natural flow regimes aims to deliver a minor flood to the lakes and surrounding floodplain three times in 10 years and a major flood once every 8 to 10 years (Murray–Darling Basin Authority 2012). In 2014/15 and 2015/16 we experimentally assessed changes in predation rates on artificial nests of freshwater turtles, using a non-randomised intervention design to test the hypothesis that a short period of poison baiting of a local fox population can significantly reduce nest predation rates (Robley et al. 2016a, 2016b). Results from that work showed that while the broad-scale fox control program did reduce the fox population, the level of reduction was insufficient to significantly reduce the level of predation on the artificial turtle nests. It was recommended that a more intensive fox control program be undertaken, including targeting of the lake edge using a target-specific bait. In 2016/17 we undertook an 11-week baiting period with non-toxic free feeding prior to the baiting program. We had hoped to conduct a 17- week baiting program, change baits every few days and deploy more bait stations based on the recommendations that came out of the work in year one.

12 Hattah-Kulkyne fox control and turtle nest monitoring

This report details the outcomes of the third year of the Ramsar Lake Protection Project investigating strategies for protecting natural resource values associated with the return to natural water flows into the Hattah Lakes system. The objective of this work was to assess the effectiveness of the revised fox control strategy at protecting Eastern Long-necked Turtle nests at HKNP, and to make recommendations for future management actions and research.

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Hattah-Kulkyne fox control and turtle nest monitoring 13

2 Methodology

2.1 Study site This study was located in the Hattah–Kulkyne National Park in north-west Victoria (34° 38' S, 142° 23' E; Fig. 1). The study area covered the Hattah–Kulkyne lakes system, which is part of the Murray River floodplain. Twelve lakes are listed under the Ramsar Convention (Department of Sustainability and Environment 2003) and cover an area of ~1155 ha (Murray–Darling Basin Authority 2012). We selected three lakes to be included in this study: Konardin (121 ha), Mournpall (243 ha) and Kramen (106 ha) (Fig. 1). Lakes Konardin and Mournpall hold water for 3–7 years after filling events and Lake Kramen holds water for 1-2 years. All are important aquatic habitat for a number of bird species, native and freshwater turtles (Department of Sustainability and Environment 2003), including the Eastern Long-necked Turtle (David Wood, Murray–Darling Freshwater Research Centre pers. comm.). This study took place between November 2016 and May 2017.

Figure 1 Hattah–Kulkyne National Park study area. Black polygon – approximate fox control area. Lakes Mournpall and Konardin are within the fox control area, Lake Kramen – was a ‘control’ site located outside the fox control area. We applied a non-randomised intervention design (Harris et al. 2006) to assess predation rates on artificial turtle nests established at the three lakes before and after fox control. Our approach was to establish fox control to cover Lakes Mournpall and Konardin (the intervention, hereafter referred to as the Mournpall block), we used Lake Kramen which was outside the fox control area as a nil-treatment, or ‘control’ site. With only a small number of lakes available for applying the intervention it was not possible to randomise treatment. Our approach allowed for the determination of association between the intervention (fox control) and the outcome (post-control nest predation rates) by comparison with the pre-control nest

14 Hattah-Kulkyne fox control and turtle nest monitoring predation rates at Lakes Mournpall and Konardin to rates at Lake Kramen, but limited our ability to extend our findings to making broad generalisations.

2.2 Fox control The recommended strategy (Robley et al. 2016b) aimed to reduce fox numbers around the Mournpall block, reducing predation rates on artificial freshwater turtle nests. The strategy involved spacing bait stations 330 m apart on all roads, tracks and walking tracks; checking and replacing baits two to three times per week; alternating bait type between FoxOff and liver baits; placing baits around the edge of selected lakes using a more target-specific bait (1080-impregnated chicken eggs, or a fish-based manufactured bait); and extending the duration of baiting to 17 weeks. It was also recommended that the baiting program be proceeded and followed by 2 weeks of free-feed baiting at both the Mournpall block and the Lake Kramen site, to (i) provide an independent index of fox activity pre- and post- poison baiting, and (ii) to expose foxes to baits prior to the poisoning campaign. Free-feed baits were to be checked and replaced daily.

2.3 Monitoring foxes We used digital cameras (Reconyx RapidFire ProPC900, Reconyx, LLP Wisconsin, USA) to collect detection/non-detection data for establishing the pre- and post-baiting indices of fox abundance in the Mournpall block and around Lake Kramen. Cameras were placed at approximately 1-km intervals within 300m of tracks to cover the Mournpall Black and Lake Kramen. This resulted in 67 cameras being established across the two areas prior to fox control (Fig. 2).

Figure 2. Location of digital cameras used to assess changes in fox activity pre- and post-control at Hattah–Kulkyne National Park in 2017. A commercial predator lure (Fox Frenzy Lure, Mark Junes Lures Inc., Texas USA) applied to absorbent cloth was placed in a small, ventilated PVC cowling and secured to the ground (using a 30-cm steel peg) 2 m in

Arthur Rylah Institute for Environmental Research Client Report

Hattah-Kulkyne fox control and turtle nest monitoring 15 front of each camera (Fig. 3). Cameras were operated for a minimum period of 30 days, with each day representing a repeat survey of the monitoring site per sampling period. Images were organised following the method outlined by Harris et al. (2010) and Sanderson and Harris (2014).

Figure 3. Camera set-up for assessing fox activity before and after fox control operations.

2.4 Changes in fox abundance Assessing the change in fox populations was undertaken using an index–manipulation–index approach (Fryxell et al. 2014), using changes in two independent indices of fox abundance: the proportion of free- feed bait taken per week before and after the poisoning operation, and the number of independent images (images separated by 24 hours) captured of foxes on cameras, also before and after the poison baiting program and at Lake Kramen. Changes in these were used as an indirect measure of the effectiveness of the fox control program. We also investigated the influence of bait type (FoxOff compared with Liver) on bait-take. Analysis of the camera and bait take data was undertaken separately using Bayesian generalised linear mixed models. We assessed the ability of the two possible distributions (negative binomial and zero- inflated negative binomial) in the models to best explain the data—this allowed the partitioning of the variance component of the fixed effects into ‘bait or camera station’ and ‘period of bait checking’. Models were run in R (version 3.2.4; R Core Team 2016) statistical software package ‘BRMS’ (Buerkner 2016). Watanabe-Akaike Information Criteria (WIAC) was used for selecting the model that best described the data (Watanabe 2010).

2.5 Monitoring changes in artificial nest predation rates We constructed a total of 108 artificial Eastern Long-necked Turtle nests at 27 sites (four nests per site) around the three lakes (Fig. 4) in October 2016 before fox control commenced and then again in February 2017 which overlapped the last 8 weeks of the fox control program. The average distance between sites at a lake was 702 ± 387 m (mean ± standard deviation). Artificial nest construction, nest site selection, and the number of nests per site were based on descriptions in the literature and personal observations of Eastern Long-necked Turtle nests (Vestjens 1969; Spencer 2002; K. Howard pers. obs.). Individual nests within each site were randomly placed 5–30 m from the edge of Lake Mournpall and Konardin, and 5 - 100 m at Lake Kramen in open sandy areas. A hand trowel was used to dig a small boot-shaped chamber of ~10 - 15 cm depth (as described in Cann 1998). We used quail eggs as a

16 Hattah-Kulkyne fox control and turtle nest monitoring surrogate for turtle eggs because these have been successfully used in the past to assess fox predation rates (Spencer 2002). Five quail eggs (Quality Quail, Red Cliffs), which are similar in size to Eastern Long- necked Turtle eggs, were placed in each nest chamber, and excavated sand was backfilled into the chamber. Surface litter was lightly scattered over the entrance to visually conceal the nest. Water collected from captive Eastern Long-necked Turtle ponds was sprayed onto the eggs prior to concealment, and on the surface above the nest (to mimic fluids released by turtles at nesting) (Green 1997; Cann 1998).

Lake Konardin

Lake Mournpall

Lake Kramen

Figure 4. Location of sites where artificial Eastern Long-necked Turtle nest were constructed. At each site four nests were established = 108 individual nests. A reference image was taken of each nest, and the location of each nest recorded with a GPS. Prior to fox control, nests were to be inspected weekly for a 49-day period (n = 7 checks) and visually assessed for indications of predation (diggings, scats, tracks, remains of eggshells). Another 108 nests were established in February 2017 at different locations within the same sites in the same manner as described above and inspected weekly for 59-days (n= 8 checks) as before. This overlapped the last 8 weeks of the poison baiting in the Mournpall Block. A single camera (Reconyx RapidFire ProPC90, Reconyx, LLP Wisconsin, USA) was placed at each nest site (facing a group of nests) to aid in the identification of nest predators. The difference in the proportion of nests surviving were plotted to investigate the differences between pre- control and the final weeks of fox control.

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3 Results

3.1 Changes in fox abundances 3.1.1 Poison baiting operation The recommended baiting program could not be fully implemented. Table 1 shows the recommended approach and the implemented program. Some factors were outside the control of the MCMA, e.g., the use of 1080 impregnated chicken eggs was not approved by Department of Economic Development, Jobs, Transport and Resources (DEDJTR) and placing baits in close proximity to lake edges raised concerns about damage to culturally and environmentally sensitive areas. Table 1. Recommended and actual fox control actions. Shaded rows indicate where the recommended and implemented program differed. Recommend Strategy Implemented Program Bait spaced at 330 m intervals Bait spaced at 330 m intervals Checked and replaced 2-3 times per week Checked and replaced once per week Alternating between FoxOff, liver and chicken eggs Liver then FoxOff (but not alternating) in the pre- and post-baiting period Baits placed on roads/tracks/walking tracks and Bait placed on roads and tracks around lake edges Extend baiting to 17 weeks (Nov - March) Program ran for 12 weeks (Jan – Apr) Two weeks free feeding pre- and post-poison One week free feeding pre- and post-poison baiting, check twice per week baiting, checking three times per week

Overall, 431 poison baits were removed of the 2340 laid from 181 bait stations during the course of the baiting operation, or 18.4% of laid baits. The proportion of baits taken varied over time (Fig. 5, Appendix 1). Overall the proportion of weekly bait take was significantly lower by 24th April at the end of the baiting period (0.29, CL 0.22 – 0.38) compared to the 26th January at the beginning of the program (0.09, CL 0.05- 0.13).

Figure 5. Proportion of poison bait take per week at Hattah-Kulkyne National Park in 2017. Bars are 95% credible limits.

18 Hattah-Kulkyne fox control and turtle nest monitoring

Overall, 87% of bait stations had at least one bait taken during the course of the program. There was spatial variation in poison bait take, with relatively more baits taken in the south (Fig. 6) and fewer baits taken on the western side of the baited area.

Figure 6. Spatial pattern of poison bait take at Hattah-Kulkyne National Park in 2017. Dots size is proportional to the total number of baits taken over the course of the baiting program. Black dots = bait stations with no recorded bait take Liver baits were taken at a greater rate than FoxOff baits (Fig. 7, Appendix 3). Overall 2340 poison baits were laid, 900 FoxOff and 1440 liver baits. Of these 0.11 (CL 0.09 – 0.14) of FoxOff baits were taken and 0.24 (CL 0.21 – 0.26) of the liver baits were taken.

Figure 7. Proportion of FoxOff and liver bait taken. Bars are 95% credible limits.

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Hattah-Kulkyne fox control and turtle nest monitoring 19

Unexpectedly, the free-feed bait-take index indicated that there was a significant increase in bait take in the post-baiting period compared to before the poison baiting commenced at both in the Mournpall block and around Lake Kramen (Fig. 8, Appendix 2). The rate of free feed bait take was higher at Lake Kramen compared to the Mournpall block both before and after the baiting period.

0.35 Pre-baiting free feed 0.30 Post-baiting free feed 0.25

0.20

0.15

0.10 Proportion bait taken bait Proportion

0.05

0.00 Lake Kramen Mournpall block Figure 8. Proportion of free-feed bait taken before and after poison baiting for foxes at the Mournpall block and Lake Kramen. 3.1.2 Fox naïve occupancy and camera activity Naïve occupancy estimates (number of sites detected at/number of sites) for foxes pre-control across the Mournpall block was 0.29, this increased to 0.63 post-control. Foxes were detected at 12 sites (n=41) on 31 occasions pre-control, and post-control they were detected at 22 sites (n=41) on 52 occasions. Naïve occupancy estimates for foxes pre-control at Lake Kramen (no fox control) was 0.72, this remained unchanged post-control (0.66). Foxes were detected at 26 sites on 124 occasions in the pre-control period and in the post-control period they were detected at 23 sites (n=32) on 80 occasions. The was no significant difference in fox activity (the number of images captured on digital cameras separated by 24 hours) at the Mournpall block or Lake Kramen following fox control, although the point estimate indicted an increase at the Mournpall block and a decrease at Lake Kramen (Fig. 9, Appendix 4).

6.0

5.0

4.0

3.0

2.0

1.0 Fox activity (# images /day) images (# activityFox

0.0 Pre Post Pre Post Mournpall block Lake Kramen Figure 9. Fox activity in the pre- and post-control periods in the Mournpall block and the nil-treatment Kramen block.

20 Hattah-Kulkyne fox control and turtle nest monitoring

3.2 Nest predation rates on artificial Eastern Long-necked Turtle nests The 108 artificial turtle nests were inspected and assessed 7 times over the 49-day period between October and December 2016 and before fox baiting commenced, and during the final 8 weeks of fox control between February and April 2017. Inspections by Mallee CMA at one nest site at Lake Kramen ceased after the theft of a digital camera, reducing that data set, the remaining sites were monitored for the full 8 weeks. At lakes in the Mournpall block (i.e., Lake Mournpall and Konardin combined), nest predation rates were not significantly different pre-control (45%) compared to the last weeks of fox control (51%) (Fig. 10a). At the individual lake level results were incongruent. At Lake Mournpall nest predation rates at the end of the pre-control period were 28% compared to 64% in the final weeks of fox control. While at Lake Konardin nest survival at the end of the pre-control period was 75% compared to 38% in the last weeks of fox control. At Lake Kramen (no fox control) at the end of the pre-control period survival rate was 48%, while in the last 8 weeks of fox control period, the survival rate was only 5% (Fig. 10b), substantially lower than at Lake Mournpall and Lake Kramen.

(a) 1.0

0.8

0.6

0.4

0.2 Proportion of nests surviving

0.0 0 7 14 21 28 35 42 49 56 63 Days (b) 1.0

0.8

0.6

0.4

0.2 Proportion of nests surviving

0.0 0 7 14 21 28 35 42 49 56 63 Days Figure 10. The proportion of artificial Eastern Long-necked Turtle nests surviving pre- and post- fox control at (a) Lakes Mournpall and Konardin combined, and (b) Lake Kramen. Blue line – pre-control, red line – post control. Pre- fox control monitoring occurred between 27th Oct and 15th Dec 2017. ‘Post-fox control’ monitoring occurred between 28th Feb and 20th Apr 2018 (overlapping the last 8 weeks of fox control).

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4 Discussion

In 2014/15 and 2015/16, the Mallee Catchment Management Authority implemented a fox control strategy to protect Eastern Long-necked Turtle nests (Robley et al. 2016). In 2014/15 the strategy reduced fox occupancy across the Park by 34%, in 2015/16 no detectable reduction was observed. There was also no significant reduction in nest predation rates in either year. Learnings from those programs were used to recommend changes to the strategy, including: targeting foxes around lakes by placing baits within 20–50 m of lake edges; using 1080-impregnated eggs as an alternative, increased bait checking and replacement (Mon, Tue, Wed); using a combination of fresh meat and manufactured meat baits; extending the duration of the program; increasing the number of artificial nests; and extending the period of nest checking. Many of these recommended improvements were not able to be implemented due to a range of factors outside the Mallee CMA’s control. For example, laying baits in areas that were culturally significant or that could also cause substantial environmental impact (i.e., within close proximity to the lakes edges) was not possible, obtaining permission from DEDJTR to use 1080 impregnated chicken eggs (a registered product in other States) was not possible due to current DEDJTR policy settings and the considerable lead up time (6 – 8 months) required by the Australian Pesticides and Veterinary Medicines Authority to process applications for off-label permits. The revised fox control program for 2016/17 covered a reduced area with increased intensity, using alternate bait types, and was aimed at improving protection around two target lakes (Lakes Mournpall and Lake Konardin). These two lakes often retain water for a number of years after flooding and represent possible refuge turtle habitat in the Hattah Lakes system. Data obtained from the camera surveys of fox activity and from the free feed baiting indicated that there was no significant decline in foxes, on the contrary fox activity and free feed bait take increased in the Mournpall block post-baiting. This outcome most likely resulted from an influx of foxes in March. While the fox control undoubtedly killed foxes, it was unable to do so at a rate sufficient to overcome the combination of young of the year entering the population or immigrants entering from surrounding areas. Young of the year become independent in late summer / early autumn with a proportion of those young remaining in the natal home range and a proportion dispersing to establish new territories (Saunders 1995). In addition, there is a component of a fox population (yearlings) that do not have established territories, which ‘float’ in the landscape looking for unoccupied spaces to establish their own territory (Saunders 1995). There was a noticeable number of ‘young’ foxes in the post-baiting camera images. Bait density is a critical issue in fox control operations, and specific knowledge of what density is required to significantly reduce fox populations is still lacking, despite decades of investment in fox control across Australia. Saunders and McLeod (2007) suggest that bait density should exceed fox density, and that under most Australian conditions a bait density of 5–10 baits per square kilometre is sufficient. Bait density during the current operation around the Lake Mournpall block was ~1.5 per square kilometre. In similar trials to ours conducted at National Park and Koondrook-Perricoota Forest (NSW) in 2016 and 2017, bait densities of 4 baits per km2 have been successful in significantly increasing turtle nest survivorship (K. Howard pers. obs.). Maintaining the presence of toxic baits in the environment is also critical to successful control. As reported in Robley et al. (2016a), achieving significant reductions in foxes over a short period is achievable, but requires strict adherence to a regime of frequent (near-daily) bait replacement (Thompson and Fleming 1994; Fleming 1996). Implementation of recommendations aimed at maximising bait density (such as placing baits along walking tracks and lake edges) was not possible due to concerns over possible environmental impacts and impacts on sites of cultural significance. Bait replacement was recommended to be three times per week; in the current operation, it was on average every 7 days. Baiting also began later in the fox season this year, which meant that the rate at which young foxes may have been entering the population could have partially overwhelmed the rate at which new foxes were being killed by the baiting program.

22 Hattah-Kulkyne fox control and turtle nest monitoring

The outcomes of the indices used to measure foxes (i.e., free feed bait take, fox activity and poison bait take) are difficult to interpret. At the Mournpall block, both the free feed and camera activity indices increased, but the overall poison bait take decreased. It would be expected that foxes increase at the nil- treatment Lake Kramen site, and if this influx outstripped the rate at which foxes could be killed by the baiting program, then a similar, but lesser increase might be expected to occur at the Mournpall Block. However, the increase at Mournpall was of a similar scale (2.3 times at Lake Kramen v 3 times at the Mournpall block). This may indicate that the attractiveness of the poison bait diminished over time, or that ‘new’ foxes were neophobic to bait. The bait type used was cooked liver until the 24th March, after which FoxOff was used. However, the change occurred after bait take had decreased to a low of about 9% of baits per week. The picture at Lake Kramen is more complicated, free feed increased in the later period but camera based activity decreased. Improving knowledge of bait uptake rates and using this to model bait densities and application rates would be a useful exercise, allowing managers to include site specific information to target baiting programs to local conditions. This would be similar in approach to that undertaken for feral Cats at HKNP as part of the Mallee CMA / Commonwealth Government funded project (Robley et al. 2017). Despite the apparent lack of significant decline in fox activity, artificial nest survival rates at the treatment lakes were close to the suggested minimum level required for Eastern Long-neck Turtle populations to survive, while at the nil-treatment lake rates were well below the notional 50% survival rate. This suggests that in the absence of the fox control, nest survival rates at the treatment lakes may have been significantly higher.

Management implications The success of fox control at protecting Eastern Long-necked Turtles and other wildlife values associated with lakes and wetlands is likely to be determined by site specific conditions that will vary spatially and temporally. This is evidenced by the contradictory results from Lake Mournpall and Lake Konardin, and the results from the previous years’ work at HKNP. A similar project at Barmah National Park and Koondrook- Perricoota State Forest (NSW) involving a short-term intensive fox control program has demonstrated reduced fox predation on turtle nests and increased turtle nest survival rates above 50% (K. Howard pers. comm.) while in this study fox control did not significantly change the rate of nest predation (45% pre- baiting; 51% post-baiting). The drivers for the differences in success are unclear, but are likely a combination of the successful operational delivery of the control program, environmental factors driving fox and turtle population dynamics, and the physical landscape. At HKNP the bait density was low compared to that achieved at Barmah and Koondrook-Perricoota, which appears to be a key factor in success. Access to wetlands at Barmah and Koondrook-Perricoota allowed baits to be laid within 20 m of the wetland edge, while at HKNP the baiting was confined to the main tracks away from the lakes edges and limited in some years by flooding over roads and tracks. Both Barmah and Koondrook-Perricoota are relatively narrow sites boarded on one side by the Murray River, while HKNP is open and unbounded, this may influence the rate of recolonization by adjacent foxes. Foxes may also increase their use of lakes edges at a time when turtles are increasing their movement to take advantage of ephemeral lakes (Kennett and Goerges 1990) created by flooding events. There is some evidence to suggest that the timing of nest predation at HKNP in 2016 was linked to the arrival of environmental flows (Robley et al. 2016b). These outcomes highlight the operational rigour required for successfully implementing fox control operations in these environments. Increasingly, land managers are required to demonstrate the cost– benefit of pest-control programs and to justify the investment of scarce public resources. In order to achieve the desired outcome from an investment, adequate resources and agile workflow management are required for accommodating the operational and monitoring requirements needed to protect lake and wetland values. Further investigations are needed to; improve our ability to implement fox control near lakes at HKNP; improve our knowledge of predator–bait encounter rates and bait consumption rates allowing for Arthur Rylah Institute for Environmental Research Client Report

Hattah-Kulkyne fox control and turtle nest monitoring 23 improved baiting strategies; and ways to use control tools that target or mimic seasonal resources that predators are utilising. Understanding how freshwater turtles use the lake system at HKNP, including nesting habitat, triggers for overland movement and nesting timing would also increase land manager’s ability to refine control actions to protect this species.

24 Hattah-Kulkyne fox control and turtle nest monitoring

References

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Appendices

Appendix 1. Bayesian linear mixed model output for weekly poison bait take at Hattah–Kulkyne National Park Table A2.1 Model output for proportion of poison baits taken at Hattah–Kulkyne National Park Population-Level Effects Estimate Estimate Error l-95% CI u-95% CI Week 1 -1.21 0.14 -1.48 -0.95 Week 2 -1.3 0.14 -1.6 -1.03 Week 3 -1.73 0.18 -2.11 -1.4 Week 4 -1.19 0.14 -1.48 -0.93 Week 5 -0.99 0.12 -1.23 -0.76 Week 6 -1.93 0.2 -2.33 -1.56 Week 7 -2.44 0.25 -2.96 -1.97 Week 8 -1.93 0.19 -2.32 -1.57 Week 9 -2.63 0.28 -3.22 -2.13 Week 10 -2.22 0.22 -2.66 -1.82 Week 11 -2.64 0.27 -3.19 -2.15 Week 12 -1.64 0.17 -1.99 -1.32 Week 13 -2.44 0.24 -2.95 -2.00

Family Specific Parameters Estimate Estimate Error l-95% CI u-95% CI Posterior distribution 97.65 77.15 19.48 298.29

Appendix 2. Bayesian linear mixed model output for free-feed bait take at Hattah– Kulkyne National Park Table A1.1 Model output for pre– and post–free-feed bait take at Hattah–Kulkyne National Park Population-Level Effects Estimate Estimate Error l-95%CI u-95%CI Intercept -1.88 0.11 -2.10 -1.67 Period – Pre -1.21 0.22 -1.64 -0.80 Treatment – not baited 0.67 0.19 0.30 1.04 Period: baited – not baited 0.31 0.36 -0.43 1.00

Family Specific Parameters Estimate Estimate Error l-95%CI u-95%CI Posterior distribution 58.15 61.57 5.79 233.82

28 Hattah-Kulkyne fox control and turtle nest monitoring

Appendix 3. Bayesian linear mixed model output for FoxOff and liver bait take at Hattah–Kulkyne National Park Table A3.1 Model output for liver versus FoxOff poison bait take at Hattah–Kulkyne National Park Population-Level Effects Estimate Estimate Error l-95%CI u-95%CI FoxOff -2.17 0.09 -2.36 -1.99 Liver -1.43 0.05 -1.53 -1.33

Family Specific Parameters Estimate Estimate Error l-95%CI u-95%CI Posterior distribution 88.98 68.28 16.65 271.48

Appendix 4. Bayesian linear mixed model output for fox activity at Hattah–Kulkyne National Park Table A4.1. Model out for fox activity pre- and post-control at Kramen and Mournpall in 2017 Population-Level Effects Estimate Estimate Error l-95%CI u-95%CI Intercept 0.83 0.21 0.43 1.26 Lake Mournpall -0.13 0.32 -0.75 0.52 Treatment - Pre 0.46 0.29 -0.12 1.03 Lake Mournpall: Treatment -0.88 0.46 -1.76 0.04 - Pre

Family Specific Parameter Estimate Estimate Error l-95%CI u-95%CI Posterior distribution 0.88 0.17 0.6 1.26

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