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Forest Ecology and Management 260 (2010) 822–832

Contents lists available at ScienceDirect

Forest Ecology and Management

journa l homepage: www.e lsev ier .com/ locate / foreco

rends in the activity levels of forest-dwelling vertebrate fauna against aackground of intensive baiting for foxes

ndrew W. Claridgea,b,∗, Ross B. Cunninghamc, Peter C. Catlingd, Allan M. Reide

Department of Environment, Climate Change and Water, Parks and Wildlife Group, Planning and Assessment Team, Southern Ranges Branch, P.O. Box 733,ueanbeyan, New South Wales 2620, AustraliaSchool of Physical, Environmental and Mathematical Sciences, University of New South Wales, Australian Defence Force Academy, Northcott Drive,anberra, Australian Capital Territory 2600, AustraliaFenner School for Environment and Society, The Australian National University, Canberra, Australian Capital Territory 0200, Australia33 Gellibrand Street, Campbell 2612, Australian Capital Territory, Australia18 Darby Street, Kaleen 2617, Australian Capital Territory, Australia

r t i c l e i n f o

rticle history:eceived 6 May 2010eceived in revised form 28 May 2010ccepted 31 May 2010

eywords:ustraliaorestoxammal

rendsertebrate080

a b s t r a c t

The relative activity of ground-dwelling vertebrates was monitored using tracks in sand plots for 10consecutive years across three nearby study areas in south-eastern mainland Australia. Two areas weresubject to intensive 1080 poison baiting for foxes, while one unbaited area acted as a control. At the two1080 baited sites there was a demonstrable decline in the reporting rate of fox tracks, while that of feralcats also declined concomitantly. In contrast, the reporting rate of wild dog tracks did not change. Atthe unbaited site the reporting rate of wild dog tracks increased slightly, while that of foxes remainedstable and that of feral cats declined slightly. Prevailing ecological theory would suggest that in systemswhere larger predators are reduced in activity or abundance, smaller predators should increase. This wasnot the case in our work. Instead, while the larger sized fox has decreased at baited sites, the smallersized cat has declined at a regional scale, in all likelihood against a backdrop of long-term drought anddiminished prey resources. Among the native omnivorous mammals that ordinarily fall prey to foxes,bandicoots, brushtail possums and lyrebirds increased in activity against a background of diminishing

fox activity, although these effects were not uniform at both baited sites. In contrast, at the study areawhere foxes were not baited, the activity of bandicoots, brushtail possums and lyrebirds either did notchange or diminished. Trends in the activity levels of these animals, particularly bandicoots, may havebeen moderated in part by prevailing rainfall conditions. Otherwise, habitat complexity may also helpregulate activity patterns. Land managers concerned with preserving and enhancing biodiversity needto not only focus on the baiting of introduced predators but also be mindful of habitat condition and the effects of climate.

. Introduction

Among the continents of the world, Australia has the unen-iable reputation of playing host to the worst rate of mammalxtinctions in the past two centuries (McKenzie et al., 2007). In

hat time 22 species have disappeared altogether, while a fur-her 10 species went extinct on the mainland and now largelyersist on small offshore islands (McKenzie and Burbidge, 2002).urthermore, the list of extant species threatened with extinction

∗ Corresponding author at: Department of Environment, Climate Change andater, Parks and Wildlife Group, Planning and Assessment Team, Southern Ranges

ranch, P.O. Box 733, Queanbeyan, New South Wales 2620, Australia.el.: +61 2 6229 7000; fax: +61 2 6229 7001.

E-mail address: andrew.claridge@environment.nsw.gov.au (A.W. Claridge).

378-1127/$ – see front matter © 2010 Elsevier B.V. All rights reserved.oi:10.1016/j.foreco.2010.05.041

© 2010 Elsevier B.V. All rights reserved.

continues to grow, as evidenced by ongoing additions to the Com-monwealth Environment Protection and Biodiversity ConservationAct 1999 (http://www.environment.gov.au/epbc/about/lists.html).While the factors leading to these extinctions and declines remaindebated (McKenzie et al., 2007; Burbidge et al., 2008), it seems thata variety of causal mechanisms are at work. These mechanismsoften act synergistically to exacerbate the chance of decline. Forexample, for some mammal species it is clear that the introductionof exotic predators by European man has been critical (Short, 1998;Short et al., 2002a,b; Bilney et al., 2010). In turn, predation pres-sures by these predators on native mammals have been increased

through modifications to habitat by clearing or inappropriate dis-turbance regimes (Catling, 1991; Claridge and Barry, 2000).

The European red fox (Vulpes vulpes) was first introduced intothe State of Victoria, Australia during the mid-nineteenth cen-tury for recreational hunting purposes. Since then, its distribution

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as increased widely and the species is thought responsible forhe demise of a large number of small to medium-sized ground-welling mammals, particularly those within the weight range50–5000 g from arid Australia (Saunders et al., 1995; Short, 1998;ohnson, 2006). Where fox populations are reduced effectively overlong enough time and an appropriate scale, native mammals may

espond positively (Kinnear et al., 1988, 1998, 2002, 2010; Burrowsnd Christensen, 2002; Dexter and Murray, 2009). In the State ofew South Wales, predation of native animals by the fox is viewedf as a threatening process, placing pressure on the relevant landanagement authorities to reduce them to the fullest extent pos-

ible (New South Wales National Parks and Wildlife Service, 2001).n practice, this has seen numerous baiting programs for foxesstablished around the State, particularly at sites where threatenedative species are in need of protection.

In south-eastern New South Wales, intensive baiting of foxeshrough the use of the toxin sodium monofluoroacetate (Com-ound 1080) has occurred for the past decade. Here, we report onhe outcome of these baiting efforts at two major study areas, inerms of trends in fox activity. Importantly, we also simultaneously

onitored the activity of sympatric predators including wild dogsdingo Canis lupus dingo, domestic dog Canis lupus familiaris andybrids of the two; Fleming and Korn, 1989) and feral cats (Felis cat-us), as well as native vertebrate species thought likely to respondositively to baiting of foxes. This offered the opportunity to explorehether the status of other species altered during the period of

nvestigation. While not the focus of baiting efforts, wild dogs anderal cats (in particular) have also been variously implicated in theemise of native fauna (Johnson, 2006). Of the native vertebrateaxa most likely to benefit from baiting of foxes, we monitored theesponse of medium-sized marsupials, birds and large-sized herbi-ores (Dickman, 1996). Critically, we also had a third study area inhe same geographic region where no baiting of foxes was under-aken, so that the trends observed in the treated sites could be putn better context (Reddiex and Forsyth, 2006).

We were particularly interested in answering the followinguestions: (i) have there been observable declines in the activity

evel of foxes at sites where baiting has been instigated, relativeo the area within which no baiting of foxes has taken place? (ii)as the activity level of other carnivores also changed over time?iii) has the activity level of any of the species of native vertebratesikely to respond positively to baiting of foxes altered? and (iv) canny of the changes in activity patterns of vertebrate taxa acrosshe three study areas be attributed to other factors such as prevail-ng climate and altered habitat attributes? To investigate trends inctivity levels of these vertebrate groups we have used a novel sta-istical approach, first developed by Cunningham and Olsen (2008)o examine changes in the reporting rates of other faunal groups inustralia. The methodological approach chosen may have broaderpplication to other studies wanting to examine temporal trendsn reporting rate of fauna using highly variable datasets.

. Methods

.1. Study areas

Three study areas were chosen for monitoring the activity ofround-dwelling vertebrate fauna: Ben Boyd National Park (here-fter Ben Boyd), where intensive baiting of foxes was implemented,outh-East Forest National Park – Genoa Section (hereafter Genoa)

here foxes were also targeted, and Nadgee Nature Reserve (here-

fter Nadgee) where no baiting was undertaken (Fig. 1). Ben Boyds approximately 25 km south of the township of Eden in south-astern New South Wales. Most of the southern section of the parks less than 160 m above sea level and the landscape is gentle to

anagement 260 (2010) 822–832 823

undulating. The geology is mainly comprised of metamorphosedDevonian sediments and associated sandstones giving rise to free-draining sandy soils except in riparian areas where drainage isimpeded. Immediately along the coast, tertiary dune systems dom-inate. Average mean maximum temperature at nearby GreencapeLighthouse is 18.2 ◦C while average mean minimum temperatureis 12.5 ◦C, with summer highs and winter lows. Average annualrainfall is around 750 mm, which is relatively evenly distributed,with lows in late winter and highs in January. The resultant veg-etation is of open forest and woodland dominated by a range ofeucalypt species, including silvertop ash (Eucalyptus seiberi), redbloodwood (Corymbia gummifera), red ironbark (E. sideroxylon) andbrown stringybark (E. baxteri). Common woody shrubs includeblack she-oak (Allocasuarina littoralis), coastal tea tree (Leptosper-mum laevigatum), bracelet honey-myrtle (Melaleuca armillaris),black wattle (Acacia mearnsii), narrow-leaved geebung (Persoonialinearis), narrow-leaved paperbark (M. linariifolia), coast banksia(Banksia integrifolia), saw banksia (B. serrata), sweet pittosporum(Pittosporum undulatum) and silky hakea (Hakea sericea). Groundvegetation includes mat rush (Lomandra longifolia), common heath(Epacris impressa), fishbone water-fern (Blechnum nudum), falsebracken (Culcita dubia), common bracken (Pteridium esculentum)and red-fruit saw-sedge (Gahnia sieberiana). Ben Boyd was previ-ously State Forest, and has a history of repeated prescribed burning,particularly during the 1970s. The last significant wildfire in thestudy area was in 1980/81.

Nadgee lies immediately to the south of Ben Boyd National Parkbut is separated by Disaster Bay and the Wonboyn River and estu-ary. Occupying an area of around 21,000 ha, Nadgee also abutsthe 87,500 ha Croajingalong National Park in adjacent Victoria.Together, Nadgee and Croajingalong form an extensive area freefrom fox control and also support a large population of wild dogs.Nadgee itself contains a variety of coastal landforms including dis-sected low tablelands, coastal plain, estuaries, coastal lagoons andbeaches (New South Wales National Parks and Wildlife Service,2003). The geology and climate are very similar to that found inBen Boyd. Open forests are the most widespread vegetation typeat Nadgee, occupying ridges, hills and well-drained coastal areas.The dominant tree species in these forests is silvertop ash, withan understorey mostly comprising of wattles (sunshine wattle A.terminalis), saw banksia, black she-oak, geebung (Persoonia levis)and common bracken. Other eucalypts such as white stringybark(E. globoidea), yellow stringybark (E. muellerana), monkey gum (E.cypellocarpa) and red bloodwood occur in moister locations. Coastalscrubs and heaths occur behind beaches and headlands along thelength of the reserve: common woody shrubs include bracelethoney-myrtle, coast banksia, coastal tea tree, silky hakea and coastwattle (A. longifolia). An extensive, high intensity wildfire burntmuch of the reserve in 1972, with another major wildfire recordedin 1980 in the northern and central part of the reserve.

The Genoa study area is approximately 30 km south-east of thetownship of Bombala. There, the annual mean maximum tempera-ture is 18. 4 ◦C while average mean minimum temperature is 4.8 ◦C,with summer highs and winter lows. Average annual rainfall isaround 640 mm, which is relatively evenly distributed, with slighthighs in the spring and summer months. Much of the study areahere is comprised of coastal foothills of moderate to undulatinglandform, lying between 400 and 750 m in elevation. Underlyinggeology is mostly Devonian or Silurian granitoids, or Ordovicianmetasediments giving rise to free-draining sandy soils (New SouthWales National Parks and Wildlife Service, 2006). Forest types vary

across the study area, although the predominant tree species aresilvertop ash, white stringybark and monkey gum. In moister andhigher elevation sites, messmate (E. obliqua) and brown barrel (E.fastigata) are the most common overstorey tree species. Under-storey vegetation is highly variable: in drainage lines ferns and

824 A.W. Claridge et al. / Forest Ecology and Management 260 (2010) 822–832

hting

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Fig. 1. Map of south-eastern Australia highlig

edges are common, while on slopes wattles and fireweed (Good-nia ovata) form thickets. A proportion of the study area was Stateorest up until the 1990s. In these areas intensive logging was car-ied out, resulting in an increase in area of regrowth eucalypt forest.roadscale and repetitive use of prescribed fire was also a manage-ent activity. The last major wildfire occurred in the summer of

982/83.

.2. Fox baiting

At Ben Boyd and Genoa, 1080 poison baiting targeting foxesas carried out as per general guidelines in the New South Wales

ox Threat Abatement Plan (New South Wales National Parks andildlife Service, 2001). In practice, this saw the establishment of a

eries of permanent stations placed at 500–1000 m intervals alonginor vehicular trails across both study areas. At Ben Boyd up

o 40 stations were used at any one time while at Genoa up to0 stations were used. At each station, foxes were targeted withither commercially made Foxoff® baits (Animal Control Technolo-ies, Melbourne, Victoria, Australia) loaded with 3 mg of 1080,r air-dried meat baits loaded with 6 mg of 1080. Regardless ofait type, baits were buried under the soil-litter interface (a legal

equirement) at each station to depths of 10–20 cm to reduce thehance of being detected and consumed by native carnivores suchs the spotted-tailed quoll (Dasyurus maculatus) (Murray and Poore,004). Other species likely to interact with and die from 1080 baitsere wild dogs and feral cats. The rate at which 1080 baits were

three main study areas described in the text.

placed at each station varied from 1 year to the next. Typically,1080 baits were placed at monthly intervals at each bait stationfor 6–8 consecutive months: baiting was generally not undertakenduring warmer summer months (December–February) due to highlevels of interference at bait stations by the large reptile the goanna(Varanus varius). As stated elsewhere, at Nadgee no 1080 baiting offoxes was carried out.

2.3. Detection of vertebrate fauna

In each of the three study areas the presence of differentground-dwelling vertebrate fauna was recorded by measuring theoccurrence of their distinctive foot tracks in a series of raked sandplots. Sand plots are raked surfaces of soil approximately 1 mwide and spanning the width of minor vehicle trails and tracks(Newsome et al., 1983). Sand plots have been used routinely inmonitoring studies of a variety of fauna, both in Australia and over-seas (i.e. Catling and Burt, 1994, 1995, 1997; Engeman et al., 2000;Catling et al., 2005; Coates, 2008), and are a highly effective andnon-invasive way to measure the presence of many taxa (Catlinget al., 1997). Other techniques such as live-trapping, which haveproven useful in other studies monitoring change in the abundance

of native ground-dwelling mammals (Dexter and Murray, 2009)were not considered for economic and logistical reasons.

In practice, 75 sand plots, each at 200–250 m spacing, wereestablished at Ben Boyd, 125 sand plots at similar spacing atGenoa and 132 sand plots at Nadgee. The differing number of plots

and Management 260 (2010) 822–832 825

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eflected the differing geographic extent of each study area (i.e. Benoyd the smallest, Nadgee and Genoa the largest). Otherwise, thepatial arrangement of sand plots varied slightly across each studyrea, since plots could only be placed on low-use vehicular trailsith relatively intact vegetation either side. At Ben Boyd plots were

rranged in three separate transects of 25 plots; at Genoa thereere five separate transects of 25 plots each, and; at Nadgee all 132lots were connected along existing trail networks. Despite theseinor variations, sand plots were distributed equitably across each

tudy area, allowing meaningful recording of changes in activity ofey fauna species.

The presence and absence of vertebrate fauna tracks wasecorded over 19 consecutive sessions from spring 1999 to spring008, concurrently, at each of the three study areas. A sessionomprised reading sand plots for three consecutive nights. In anyiven year, two sessions were completed: once in autumn–winterMarch–June) and once in spring–summer (August–December). Onfew occasions, sessions and/or a complete set of plots were unable

o be completed due to poor weather, but these were by far thexception rather than the rule. Fig. 2 shows the temporal cover-ge of sampling of plots from across the three study areas over theifetime of the study.

Tracks from three different carnivores were distinguished onand plots: wild dogs (Canis lupus familiaris, C. lupus dingo andybrids of the two), foxes (V. vulpes) and feral cats (F. cattus).mong native omnivores and herbivores, tracks of ‘bandicoots’ere potentially made by two species, the southern brown bandi-

oot (Isoodon obesulus) and the long-nosed bandicoot (Peramelesasuta). Similarly, ‘brushtail possum’ tracks may have comprisedwo different species, the common brushtail possum (Trichosurusulpecula) and the mountain brushtail possum (T. caninus). Trackseft by ‘macropods’ were of three different species: the easternrey kangaroo (Macropus giganteus), red-necked wallaby (Macro-us rufrogriseus) and the swamp wallaby (Wallabia bicolor). Otheraxa of interest recorded from tracks on plots included the goanna,yrebird (Menura novaehollandiae) and wombat (Vombatus ursinus).

.4. Rainfall patterns

Across the period of study we were interested in the broadelationship between trends in the reporting rate of each of theertebrate taxa recorded on sand plots and annual rainfall. Exam-ning this relationship was important since previous studies havehown that the population dynamics of a range of animal speciesn Australia vary depending on long-term patterns of precipitationLunney, 1987; Recher et al., 2009). Rainfall data for the periodtart-1998 to end-2008 were obtained from the Commonwealthf Australia Bureau of Metereology website. For the Genoa studyrea we used rainfall data collected at the township of Bombala,pproximately 25 km to the north-west (http://www.bom.gov.au/limate/averages/tables/cw 070005.shtml). For both Ben Boydnd Nadgee we used rainfall data from the nearby Greencapeighthouse weather station. Greencape is located 5 and 10 km,espectively, from each study area (http://www.bom.gov.au/limate/averages/tables/cw 069005.shtml). For each year of study,rainfall anomaly was calculated by subtracting the total amountf rainfall received for that year from the long-term average annualainfall figure. In this way, rainfall could be described for each years above, below or on average (Dexter and Murray, 2009).

.5. Measuring structural change in forest complexity

Structural features of habitat such as cover of vegetation,mount of coarse woody debris and leaf litter can influence theelative abundance of different vertebrate taxa in Australian forestystems (Catling and Burt, 1994, 1995, 1997). We estimated habi-

Fig. 2. Plot showing temporal sampling of sand plots in each of three study areasduring the period 1999–2008. White background means no sampling undertaken.

tat complexity at each sand plot site on four occasions during theperiod of study: 1999, 2002, 2005 and 2009 in Ben Boyd and Genoaand 2000, 2002, 2004 and 2007 in Nadgee. To do this, we used themethods of Catling and Coops (1999) and Coops and Catling (1997).In brief, this involved making a visual assessment of five differentattributes: (i) the amount or cover of vegetation in the trees, (ii)understorey vegetation cover, (iii) ground layer vegetation cover,(iv) cover of amount of litter, rocks and fallen logs, and (v) an indi-cator for degree of wetness. Each of these features was scored on a0–3 scale and the resultant scores then tallied. Thus, a tallied scoreof 4 or 5 denotes a forest with low habitat complexity, a score of 7or 8 moderate habitat complexity and anything above 9 or 10 highhabitat complexity. For ease of recording, scores were made for the

five attributes from two 25 m × 20 m rectangles either side of eachsand plot. An average score for a given attribute was calculated bydividing the scores reported within each rectangle by two.

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26 A.W. Claridge et al. / Forest Ecology

.6. Analysing trends in reporting rates

A reporting rate was calculated for each of the taxa recognisedbove for each session across all years of observation. Plots where aaxa was recorded on any or all of the 3 days received a score of ‘1’,hile plots where a taxa was not recorded at all received a score

f ‘0’. The reporting rate was calculated as the percentage of plotshat had recorded positive evidence of those taxa over the 3-dayampling period. For example, if foxes had been recorded on 25 ofhe 75 plots at Ben Boyd for a sample session, the reporting rateas 25/75 or 33%.

Plots of reporting rates for each of the taxa identified from trackshowed high intra-year and inter-year variation and did not providelear insight into long-term temporal trends. In view of this vari-tion we instead employed the methodology of Cunningham andlsen (2008), using a generalised linear modelling (GLM) frame-ork. In brief, this first involved fitting regression splines with two

nots to highlight long-term trends. With regression splines, poly-omials are fitted to segments of the data where the segmentsre separated by a sequence of user-defined ‘knots’. The piecewiseolynomials are belted together at these ‘knots’. The method oftting used was a weighted least-squares for over-dispersed pro-ortions. Regression splines are very flexible and the degree of

roughness’ can be easily modified: we used a “smooth” smooth.he statistical model does not explicitly account for possible serialependence arising from the fact that data are repeat measures ofhe same plots. Instead, the repeat measures structure of the dataas preserved for inference (Cunningham and Olsen, 2008).

Interpretation of trend curves requires knowledge about therecision of a trend line. By calculating approximate confidence

ntervals an assessment of whether long-term changes are statis-ically significant can be made (Cunningham and Olsen, 2008). Inhe current case the bootstrap method was used to obtain approx-mate confidence intervals of smooth curves for individual species.his eliminated the need for back-transforming standard errors andeeting assumptions used in parametric analysis such as indepen-

ence. The bootstrap method used drew on 500 random samples ofavailable sites, with replacement, from the original N sites. Each

ample was then treated as actual data and the modelling processutlined above was followed to obtain a new trend curve. Afterll 500 replicates were completed, fitted values for each sampleoint was sorted into ascending order and the 5th and 95th per-entiles computed. The repeated measures nature of the data wasccounted for by re-sampling plots, and not observations.

As well as estimating a general smooth curve, the linear trendas computed. Such a trend should be interpreted with caution

iven the true trends in the data. To assist with interpretation, thetatistical significance of the linear trend was assessed by com-aring the actual trend with the 500 bootstrap estimates, and

significant’ trends were those that fell within the 5% tail of theootstrap estimation.

The analysis provided a smooth trend curve that tracked changeor each species. The respective curvature properties of the trendines were further assessed by calculating the second derivate ofhe trend curve. If the second derivate is >0 then the curve is turn-ng upward; if it is <0 then it is turning downward; and if at 0t changing at a steady rate or not at all. Where change pointsccurred in the trajectory this was signified on the trend line by:green circle for a significant acceleration in the rate of change,hich happens around troughs as the reporting rate bottoms out

nd then begins to rise; and blue circles for a deceleration, which

ccurs over peaks. These markers indicate ‘acceleration’ and ‘decel-ration’ of the curves, respectively, and not ‘significant’ increasingnd decreasing reporting rates (Cunningham and Olsen, 2008).

Trend lines are presented graphically for individual taxa as perunningham and Olsen (2008). This involves highlighting six major

anagement 260 (2010) 822–832

attributes: (i) the actual pattern in reporting rate is plotted overtime as a thin solid black line, (ii) the ‘smooth fit’, plotted as thicksmooth black line, obtained by fitting a regression spline, (iii) the5th and 95th percentiles, based on 500 bootstrap samples, are rep-resented by thin dotted black lines, (iv) a linear fit (smoothing splineof order 1) shown as a red line. If statistically significant (in thelower or upper 5th percentiles it is indicated as a bold, thick line), (v)‘significant’ change points indicated by blue dots, marking a slow-ing in the rate of change or deceleration, and green dots, markingan increase in rate of change or acceleration, and (vi) a sub-graphor rug plot showing the relative sample size for each month, whichrelates to the precision of the estimates at each sample session.

3. Results

3.1. Trends in reporting rates of carnivores

The linear trend for reporting rate of feral cats decreased signif-icantly at Ben Boyd over the time of study, in the absence of anytargeted baiting effort (Fig. 3a). The modelled response highlighteda peak in activity around Autumn 2003 and a trough in Autumn2007. The linear trend for cats at Genoa similarly decreased sig-nificantly over time, with a peak also in Autumn 2003 and troughin Autumn 2007 (Fig. 3b). Prior to the peak in Autumn 2003, catactivity troughed at this study area in Autumn 2001. Overall report-ing rates between Ben Boyd and Genoa were roughly comparableacross the period of study.

At Nadgee the trend for reporting rate of cat tracks followed asimilar pattern, with an overall significant linear decline over time(Fig. 3c). In addition, when the smooth fit was modelled there was acoincident peak in reporting rate around Autumn 2003 and a troughin Autumn 2007. The overall actual and modelled reporting ratesof cat tracks were less than that reported from both Ben Boyd andGenoa.

At Ben Boyd, in the presence of intensive 1080 baiting, the lin-ear reporting rate of foxes declined significantly since inceptionof the baiting program in spring 1999 (Fig. 3d). There was a sig-nificant change point in reporting rate from Autumn 2001, afterwhich a trough in activity was recorded through until Spring 2006.Since then there appears to have been an increase in reporting ratethrough to Spring 2008.

At Genoa, where intensive 1080 baiting is also carried out, thelinear reporting rate of foxes has also declined significantly sinceinception of the program in Spring 1999 (Fig. 3e). However, thelinear trend did not fully account for changes in fox activity overthe program. The smooth trend curve for fox activity indicates atrough commencing in Spring 2000 through Spring 2002, followedby a slight second peak, albeit at a lower level than at the start ofthe program, around Spring 2005.

At Nadgee, in the absence of 1080 baiting, the linear reportingrate of foxes has not changed significantly since commencement ofmonitoring, although the smooth fit for the data indicates chang-ing reporting rates over time (Fig. 3f). A decline in reportingrate of fox tracks was noted around Spring 2004 and a peak inreporting rate around Autumn 2007. Overall, the reporting rate offox tracks at Nadgee has remained higher than at Ben Boyd andGenoa.

At Ben Boyd, the linear fit indicated a significant increase inreporting rate of wild dog tracks over time, with troughs in activityaround Spring 2001 and Autumn 2006 (Fig. 3g). In contrast, the lin-

ear fit for change in activity of wild dog tracks at Genoa showed nosignificant change over time (Fig. 3h). However a peak in activitywas noted for Autumn 2007 and a trough in Spring 2003.

At Nadgee the reporting rate of wild dog tracks showed a sig-nificant linear decline over time since inception of the monitoring.

A.W. Claridge et al. / Forest Ecology and Management 260 (2010) 822–832 827

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ig. 3. Trends in the relative activity of ground-dwelling carnivores across three stines.

he linear fit did not fully account for changes in reporting rate ofracks over time, with troughs around Autumn 2001 and Autumn007 and a peak around Spring 2003 (Fig. 3i).

.2. Trends in reporting rates of medium-sized ground-dwellingertebrates

Across the entire sampling period, the reporting rate of bandi-oot tracks at Ben Boyd showed a significant linear decline overime across the entire sampling period (Fig. 4a). However, the lineart did not fully account for variations in reporting rate of bandi-oot tracks. When smooth trends were plotted, there were troughsn reporting rates of bandicoot tracks around Autumn 2001 andutumn 2007 and a peak in Autumn 2004. This indicates that bandi-

oot activity has cycled over time.

In contrast, at the Genoa study area, the activity of bandicootracks has shown a significant linear increase since Spring 1999Fig. 4b). The linear fit did not fully account for changes in report-ng rate of bandicoot tracks, with a trough reported during the

eas in south-eastern New South Wales, Australia. See text for explanation of trend

period Spring 2004 and peaks around Autumn 2002 and Spring2007. Overall, the actual as well as modelled reporting rate forbandicoot tracks was lower at this study area relative to that atBen Boyd and Nadgee.

At Nadgee, the reporting rate of bandicoot tracks followed a sim-ilar cyclic trend to that occurring in adjacent Ben Boyd. Over thesampling period there was a significant linear decline in reportingrate of tracks (Fig. 4c). Like Ben Boyd, when the smooth trends wereplotted for Nadgee there were coincident troughs in reporting ratesaround Autumn 2001 and Autumn 2007 and a coincident peak inAutumn 2004.

At Ben Boyd, the linear fit for reporting rate of brushtail possumtracks showed a significant increase since inception of the 1080baiting program in Spring 1999, with a peak in reporting rate about

Spring 2005 (Fig. 4d). A similar trend was apparent for brushtailpossum tracks at Genoa, where the linear fit indicated a significantlinear increase over time, coinciding with a peak around Autumn2006 (Fig. 4e). Overall reporting rates were higher at Genoa than atBen Boyd.

828 A.W. Claridge et al. / Forest Ecology and Management 260 (2010) 822–832

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ig. 4. Trends in the relative activity of medium-sized native ground-dwelling omnxplanation of trend lines.

At Nadgee the linear trend for reporting rate of brushtail pos-um tracks did not change significantly during the study period,lthough the smooth fit indicated a peak in reporting rate aroundutumn 2003 (Fig. 4f). The overall reporting rate of possum tracksas less than that recorded at Ben Boyd and Genoa.

The reporting rate of lyrebird tracks at Ben Boyd showed a signif-cant linear fit increase over the duration of the study (Fig. 4g). Themooth regression model for this taxa further highlighted that theinear fit did not capture intermittent changes in reporting rate ofyrebirds, with a peak in activity around Spring 2004 and troughs inpring 2000 and then again Spring 2007. In contrast, at Genoa thereas no demonstrable or significant overall change in the report-

ng rate of lyrebird tracks over time (Fig. 4h), although a trough inctivity was reported around Autumn 2001. At Nadgee the lineareporting rate of lyrebird tracks did not change significantly overime (Fig. 4i). Overall, the reporting rate of lyrebird tracks at Nadgeeas less than that recorded at Ben Boyd and Nadgee.

across three study areas in south-eastern New South Wales, Australia. See text for

3.3. Trends in reporting rates of large-sized ground-dwellingvertebrates

At Ben Boyd the reporting rate of goanna tracks showed a signifi-cant increase during the period 1999–2008 (Fig. 5a). For the smoothfit for this relationship, a peak was observed around Spring 2002.In contrast, at Genoa, the reporting rate of goanna tracks showedno significant linear trend over time. Instead, a peak in reportingrate was recorded around Spring 2002 (Fig. 5b).

At Nadgee the reporting rate of goanna tracks has shown a sig-nificant linear increase over time, with a peak around Autumn 2001,roughly consistent with that reported at adjacent Ben Boyd (Fig. 5c).

Unlike the latter site, the reporting rate of goanna tracks at Nadgeetroughed around Autumn 2006.

At Ben Boyd, the reporting rate of macropod tracks showeda strong linear decline over time since inception of the program(Fig. 5d). From the smooth fit for this relationship, a slowing down

A.W. Claridge et al. / Forest Ecology and Management 260 (2010) 822–832 829

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of monitoring was −543.4 mm, indicating a period of mostly pro-

ig. 5. Trends in the relative activity of large-sized native ground-dwelling omnivxplanation of trend lines.

n this decline occurred during the period Spring 2000 throughpring 2002. In contrast, at Genoa, the reporting rate of macropodracks showed a significant linear increase over the duration of therogram. The linear fit did not adequately describe change in theeporting rate of tracks over time. The smooth fit indicated a troughn reporting rate around Autumn 2001 and a peak around Autumn004 (Fig. 5e)

At Nadgee the reporting rate of macropod tracks showed a sig-ificant linear increase over the duration of monitoring (Fig. 5f).he linear trend did not fully account for changes in reporting ratever time. The smooth fit indicated a trough in reporting aroundutumn 2004, and peaks around Autumn 2002 and Autumn 2007.

The reporting rate of wombat tracks at Ben Boyd showed a sig-

ificant linear decline over time (Fig. 5g). The linear fit did notapture changes in reporting rate during the period of investiga-ion, with the smooth fit indicating troughs in reporting aroundutumn 2001 and Autumn 2007 and a peak around Autumn 2004.t Genoa, there was a strong linear increase in reporting rate of

cross three study areas in south-eastern New South Wales, Australia. See text for

wombat tracks over time (Fig. 5h). At Nadgee the trend in report-ing rate of wombat tracks was similar to that recorded at adjacentBen Boyd, with a significant linear decline over time (Fig. 5i).

3.4. Rainfall patterns

Rainfall patterns across the study period are highlighted inTable 1. For Ben Boyd and Nadgee study areas, weather data fromthe nearby Greencape Lighthouse indicates that between 1998 and2008, only 3 years provided above-average annual rainfall; 1999,2003 and 2007. Overall, the total rainfall deficit across the decade

longed drought. For the Genoa study area, rainfall data from nearbyBombala Township also indicated an overall drought for the previ-ous decade, with an overall deficit of −705.3 mm. This is roughlyequivalent to a single year of annual average rainfall. Only 3 yearsproduced above-average annual rainfall; 2001, 2005 and 2007.

830 A.W. Claridge et al. / Forest Ecology and Management 260 (2010) 822–832

Table 1Annual rainfall (mm) at the two nearest weather stations to the Ben Boyd, Genoa and Nadgee study areas. Rainfall at Greencape Lighthouse is broadly reflective of rainfallat Ben Boyd and Nadgee, while that at Bombala Township is indicative of rainfall at Genoa. LTA = long-term average annual rainfall. Deficit is calculated for each year bysubtracting the rainfall from that year from the LTA. All rainfall data obtained from the y website (www.bom.gov.au).

LTA 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Bombala Township 640.3 505.8 566.4 616.4 775.4 515.6 498.0 491.8 775.6 498.8 664.4 429.8Deficit −134.5 −73.9 −23.9 135.1

Greencape Lighthouse 739.3 719.0 963.3 617.8 668.9Deficit −20.3 224.1 −121.5 −70.4

Table 2Habitat complexity scores across sand plots in each of the three study sites in south-eastern mainland Australia.

1999 2002 2005 2009

Ben BoydMean 6.7 6.7 7.1 6.7S.D. 0.9 0.9 0.8 1.0

GenoaMean 6.4 6.4 6.6 6.3S.D. 0.9 0.9 0.9 1.0

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NadgeeMean 7.8 7.8 7.8 7.7S.D. 1.5 1.5 1.5 1.4

.5. Changes in habitat complexity

Over the period of our study the average habitat complexitycores across sand plots within each study area did not changeignificantly or changed only marginally (paired two-tailed t-testssuming unequal variance: Ben Boyd 1999–2009, p > 0.5; Genoa999–2009, p = 0.46; Nadgee 1999–2009, p > 0.5; Table 2). The aver-ge habitat complexity scores were roughly equal between Benoyd and Genoa, but generally higher in Nadgee (on average aboutpoint higher on the scoring system; Table 2).

. Discussion

.1. Response of carnivores to baiting

In Australian ecosystems introduced predators such as the redox have had a large impact on native mammals over a relativelyhort timeframe since European human settlement (Johnson, 2006;ilney et al., 2010). Recent emphasis by land management agenciesn broad scale and intensive baiting campaigns for these pests areell meaning but few programs have demonstrated the benefits

f fox baiting both in terms of reducing foxes and, more impor-antly showing benefit for native prey (Burrows and Christensen,002; Reddiex and Forsyth, 2006; Dexter and Murray, 2009). In ourtudy, long-term trends in reporting rate of fox activity on sandlots shows that baiting efforts are being effective at Ben Boydnd Genoa, where long-term and intensive use of 1080 poison hasccurred over a 10-year period. In contrast, at Nadgee where noaiting has been implemented, fox activity has not changed signifi-antly over the timeframe of study, although there have been peaksnd troughs in reporting rate of fox tracks over time.

Mesopredator release theory would suggest that where foxumbers are declining, smaller carnivores such as feral cats should

ncrease their activity or population numbers (see Johnson et al.,007). In Arid zone Australia, foxes have been shown to influencehe relative abundance of cats. For example, at Roxby Downs in

he South Australian desert, Read and Bowen (2001) noted thatat densities were lowest when fox densities were highest. Simi-arly, in arid landscapes the (larger) dingo has been speculated tolso regulate abundance of smaller carnivores such as cats (Glent al., 2007). While these relationships might hold true in some

−124.7 −142.3 −148.5 135.3 −141.5 24.1 −210.5

586.4 834.0 605.7 610.6 712.0 796.3 474.8−152.9 94.7 −133.6 −128.7 −27.3 57.0 −264.5

geographic areas, they do not hold true for the area in whichwe worked. Despite declines in fox activity at the Ben Boyd andGenoa baited areas, feral cat activity did not increase over the life-time of our monitoring program. Instead, across all three studyareas cat activity declined. This decline was consistent, implyinga broader regional trend irrespective of 1080 baiting programs.While feral cats are acutely sensitive to 1080 (McIlroy, 1981; Easonand Frampton, 1991), they typically are bait shy and there are cur-rently no effective techniques to reduce their abundance (Risbey etal., 1997). Our baiting methods are thus unlikely to have had anyinfluence on feral cat populations.

The overall decline in cat activity during our study may well bedue to changes in the availability of preferred prey items. Acrossour study region, cats are known to prey on a large range of nativefauna (Triggs et al., 1984), with main prey species including ring-tail possums (Pseudocheirus peregrinus) and small mammals suchas Antechinus spp. and Rattus spp. Long-term studies of the pop-ulation dynamics of the small mammals within our study regionindicate that numbers change at least in part in relation to rainfallpatterns and the severity of drought. During the early to middle ofthe current decade, for instance, small mammal populations havedeclined in relation to drought in Nadgee (Recher et al., 2009). Thetiming of these declines is roughly coincident with the decline incat activity noted across our study plots. The possible overarchinginfluence of wild dogs on cat populations should not be discountedsince in some Australian landscapes the larger body mass dog mayhelp regulate the smaller sized cat (Johnson and VanderWal, 2009).In our study area this would require a closer inspection of the inter-actions among wild dogs and cats since simple correlation trendssuch as those gleaned from our monitoring provide little insight.In summary, the relative abundance of wild dogs, foxes and catsare clearly far more complex than that implied by mesopredatorrelease theory (see also Johnson and VanderWal, 2009).

Although the baiting programs at Ben Boyd and Genoa weretargeted toward foxes, wild dogs also interacted with 1080 baitsand individual animals undoubtedly succumbed to baiting. Despitethis, there was no evidence of decline in wild dog activity fromtracks recorded in sand plots at these sites. Instead, at Ben Boyd,the reporting rate of wild dog tracks showed a significant linearincrease over time, particularly in the last 2 years or so of the study.At Genoa, where baiting was also undertaken, wild dog activity didnot change significantly over the decade or so of monitoring. In con-trast, at Nadgee, where no baiting was undertaken, the reportingrate of wild dog tracks declined linearly over time.

4.2. Response of native fauna

Among the native taxa most likely to have showed a positiveresponse to baiting of foxes at Ben Boyd and Genoa, there were vary-ing responses. At Ben Boyd, the activity level of bandicoot tracks

cycled over time, although the overall linear trend since incep-tion of baiting was of significant decline. This pattern of declinewas also apparent in adjacent Nadgee where no baiting was under-taken. This is suggestive of some localised change in habitat quality,although our habitat complexity scores (Newsome et al., 1983) did

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A.W. Claridge et al. / Forest Ecology

ot change significantly over time. In contrast, at the Genoa studyrea, the overall linear trend for bandicoot tracks was of signifi-ant increase over time. This may be at least partially attributableo a decline in fox activity as a consequence of the baiting pro-ram.

In East Gippsland, Victoria, Dexter and Murray (2009) notedopulation increases southern brown bandicoots (I. obesulus) and

ong-nosed potoroos (Potorous tridactylus) in areas subject to inten-ive baiting of foxes. The positive response of these species was notqual across all sites at which foxes were successfully reduced, butather greater in two out of three baited sites. Of note, in the baitedite where no positive response was recorded, the vegetation typesended to be more structurally open in the understorey. In contrast,here the positive responses were noted, vegetation in the under-

torey of those sites was more structurally complex (A.W. Claridge,ersonal observations). This suggests that the degree of responsey critical-weight-range mammals to baiting of foxes may be mod-rated in part by other factors such as habitat quality (Claridge andarry, 2000). Catling et al. (2001) found a highly significant positiveelationship between abundance of bandicoots and habitat com-lexity score. Dexter and Murray (2009) also noted increases inapture rate of bandicoots and potoroos at non-baited sites overime, but at a lower rate than that observed in treatment sites.hey attributed this response to the baiting operations having auch broader impact on fox populations than just the treatment

reas, through formation of ecological traps. The increases at non-aited sites could not readily be ascribed to extrinsic factors suchs favourable climatic conditions since during the period of studyainfall was below average. Whether this is true or not deserves fur-her investigation. The positive response of bandicoots to baiting ofoxes is not limited to that described by Dexter and Murray (2009).

ithin a fenced heathland area near Melbourne, Victoria, Coates2008) noted increases in the reporting rate of bandicoot trackshen fox activity was maintained at very low levels by 1080 baiting.ver time, an increase in the range of sites occupied by bandicootsas also noted. Finally, in south-western Australia, Burrows andhristensen (2002) noted an increase in trapping success of south-rn brown bandicoots when fox baiting efforts were intensified inarrah (Eucalyptus marginata) forest.

Other medium-sized native mammals may also benefit from aeduction in fox abundance. In our study, for brushtail possumshere were a significant increase in reporting rate of tracks overime at both Ben Boyd and Genoa. This contrasted with the trendbserved at Nadgee where, in the absence of baiting, the reportingate of brushtail possum tracks did not change significantly. Dexternd Murray (2009) similarly reported an increase in numbers ofive-captured common brushtail possums in sites where foxes wereaited relative to sites where no baiting was undertaken. That said,he response of native fauna to successful baiting programs may notlways be predictable or positive. For example, Banks (1999) notedhat the number of bush rats (Rattus fuscipes) known to be alive didot change significantly in response to fox removal from montane

orest sites in south-eastern Australia. This was despite populationsf the foxes being reduced to about one-fifth of that occurring indjacent non-baited sites. Similarly, the persistence time of indi-idual rats at sites with and without effective baiting of foxes didot differ, nor did juvenile recruitment of rats into local popula-ions. The most likely explanation for the lack of positive responseas that the predation pressure on rats by foxes was low during

he experiment and mortality levels of the former were insteadegulated by other factors (Banks, 1999).

.3. Other regulating factors

Inevitably, the response of native mammals to a reductionn predation by introduced species such as the red fox may be

anagement 260 (2010) 822–832 831

complicated by other factors, such as prevailing climate and itsinfluence on habitat quality. Landscape-scale studies of nativeground-dwelling fauna undertaken over the past two decades high-light the differing importance of habitat complexity (Catling andBurt, 1994, 1995; Catling et al., 1997, 2001; Catling and Coops, 1999;Claridge and Barry, 2000). Bandicoots, for example, require habitatwith high levels of structural complexity in the forest understoreyand this can be moderated following drought, fire, or combinationsthereof (Claridge and Barry, 2000). Related long-term studies fromthe Nadgee study area show that the relative activity of bandicootswaxes and wanes in relation to structural complexity followingdrought and fire (Newsome et al., 1983; Catling et al., 2001). Smallrodents are similarly affected by a reduction in ground vegetationcover (Catling and Burt, 1994, 1995).

Rainfall also influences the activity of animals such as bandi-coots, through regulation of essential food resources such assoil-dwelling invertebrates. In heath environments, for exam-ple, primary food items including beetle larvae and hypogeous(underground-fruiting) fungi increase in relative abundance dur-ing wet seasons and subsequently decline during dry conditionsor prolonged drought (Dufty, 1994; Claridge and Barry, 2000). Ineach of our study areas, bandicoot activity was cyclic, with peaksand troughs approximately coincident at the nearby Ben Boyd andNadgee sites. In these cycles, peaks in activity matched periodswhere rainfall was close to normal or above average, while troughscorresponded to dry times. Over the decade of study the overallrainfall trend was of long-term decline. In this regard the posi-tive response of bandicoots at Genoa and the positive effect of foxcontrol is noteworthy.

Given the complexities of predation, climate and habitat, landmanagers cannot afford to adopt simplistic approaches to man-aging ground-dwelling mammals in forests (Kinnear et al., 2010).Instead, managing for structurally complex habitats in associationwith intensive and broad scale fox control programs would seemprudent. At our Ben Boyd and Genoa study areas the next logi-cal step in managing the forest system would be to attempt toincrease habitat complexity through deliberate use of disturbancessuch as fire since our measures indicate it may be below threshold(see Catling, 1991). Our 10-year baseline data provide opportu-nity to continue to follow the fate of ground-dwelling mammalsin response to these manipulations.

Finally, the complexities of the interrelationships among wilddogs, foxes and cats, and the prey they eat, need to be better articu-lated through use of novel techniques that extend beyond simplisticcorrelation analyses from associated monitoring (see Hilborn andStearns, 1982; Rozenweig and Maccarthur, 1963; Kinnear et al.,2010). These may or may not include using forensic DNA methods toestablish precisely how predator populations change in space andtime with and without perturbations such as 1080 baiting (Kinnearet al., 2010). This work is essential given the appalling history ofconservation of native mammals in south-eastern Australia, thedecline of which can mostly be attributed to exotic predators suchas the fox and feral cat (Bilney et al., 2010).

Acknowledgements

We thank the Department of Environment, Climate Change andWater, Parks and Wildlife Group Southern Branch Senior Manage-ment Team for financial support of this project. We sincerely thankMax Beukers, Shane Bobbin, Grant Brewer, Noel Browning, the late

Mick Burt, Rachel Butterworth, Steve Cameron, Mitch Cumstein,Craig Dickman, Steve Dovey, Artie Fufkin, George Malolakis, RossOhlsen and Franz Peters for considerable assistance with fieldworkand other logistical support. Christine Donnelly assisted with dataanalysis.

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in Australia—evidence for ineffective anti-predator adaptations in native prey

32 A.W. Claridge et al. / Forest Ecology

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