Scat happens: spatiotemporal fluctuation in dingoscat collection rates

Benjamin L. Allen

The University of Queensland, School of Agriculture and Food Sciences, Gatton, Qld 4343, Australia.Current address: Vertebrate Pest Research Unit, NSW Department of Primary Industries, Broken Hill,NSW 2880, Australia. Email: benjamin.allen@dpi.nsw.gov.au

Abstract. The number of dingo (Canis lupus dingo and hybrids) scats collected from an area has been used as a measureof pack stability in order to make inferences about dingo pack structures and function. In doing so, some studies samplingdifferent sites at different times/seasons have been forced to assume that scat collection rates vary little throughout the yearin order to attribute observed site/treatment differences to the effect of interventions (e.g. lethal control), rather than naturalspatiotemporal variation in scat densities. In this study, 4112 dingo scats systematically collected from adjacent dingo-baited and unbaited areas at three arid-zone sites on a regular basis over 2–4 years are used to test this assumption. Scatcollection rates varied between treatments, sites and surveys, with substantial differences occurring within a few weeksor months. Similar temporal trends between treatments at each site demonstrated that scat collection rates fluctuatedindependently of dingo control. It was concluded that observations of different scat collection rates between different sitessampled at different times may simply reflect normal spatiotemporal variability in scat densities, which may not reflectabsolute dingo abundance.

Additional keywords: Canis lupus dingo, defaecation, lethal control, pack structure, population indexing, scent-marking,social stability.

Received 30 August 2011, accepted 6 August 2012, published online 17 September 2012

Introduction

Dingoes (Canis lupus dingo and other free-roaming Canis) are acharismatic and iconic terrestrial predator associated withAustralian wilderness or outback areas. Owing primarily to theirability to kill livestock (e.g. Thomson 1984; Allen 2000; Hewitt2009) and threaten many native fauna (e.g. Coutts-Smith et al.2007; Allen 2011; Allen and Fleming 2012; Allen and Leung2012), dingoes are considered pests in many areas and are oftencontrolled with broad-scale poison baiting campaigns (Fleminget al. 2001), most commonly with the toxin sodium fluoroacetate(or ‘1080’) (APVMA 2008; Glen et al. 2007). However, recentattention has focussed on the potential benefits dingoes mightprovide to native fauna through the suppression ofmesopredators, such as foxes (Vulpes vulpes) and feral cats (Feliscatus) (Purcell 2010; Wallach et al. 2010; Letnic et al. 2012; butsee Allen et al. 2011a). Such studies have culminated in calls toprohibit lethal dingo control in livestock production areas (e.g.Carwardine et al. 2011).

Wallach et al. (2010) assessed data from several sites innorthern South Australia and concluded that ‘the destructiveinfluence of predator control even outweighed the benefits ofrain’ in the arid zone, because herbivore and mesopredatorpopulations apparently increased to overwhelming levels wheredingoes were controlled. Dingo control was expected to

negatively influencepack stability and social cohesion, ultimatelyinfluencing food webs to the point where dingoes were unableto exert top-down influence on herbivores or mesopredators(Wallach et al. 2009, 2010). Pack stability or function was notdirectly measured using conventional techniques (such asidentification and observation of individuals) (Whitehead 2008)in the original studies, but was instead inferred from the numberof dingo scats (or faeces) collected from focal points at widelydispersed baited or unbaited sites at different times (Wallach et al.2009). From these data (and opportunistic point-counts ofdingoes howling), it was postulated that dingo control disruptsthe social structure of dingo populations (Wallach et al. 2009),shifting ecosystem states away from those driven by top-downprocesses towards those driven by bottom-up processes (Wallachet al. 2010). However, because comparisons were made betweendifferent sites sampled in different seasons (Allen et al. 2011a),it was requisite to assume that scat collection rates varied littlethroughout the year (Wallach et al. 2009). If scat collection-rateswere greatly variable, the observed differences between siteswhere dingoes are or are not controlledmay simply be attributableto normal spatiotemporal variation in dingo densities or scent-marking behaviour independent of dingo control.

Previous studies of dingoes have reported seasonal andcyclical variability in ground raking (i.e. scratching), howling,

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raised-leg urination, activity on roads and waterpoint visitationrates (e.g. Corbett 2001; Purcell 2010; Allen et al. 2011a; Allen2012a), suggesting that scat accumulation rates at focal pointsmay also be influenced by seasonal factors unrelated to dingocontrol. Summarising the relevant literature up until 2001,Corbett (2001) concludes that ‘the use of scent posts [for urinationand defecation] increases during the breeding season’, whichtypically occurs between March and June in Australia. So dodingo scat collection rates in northern South Australia exhibitlittle temporal variation or not? Answering this question shouldbe a straight forward exercise requiring the systematic collectionof dingo scats over a sufficient period. Such an undertakingoccurred between 2008 and 2011 in northern South Australia aspart of a large-scale manipulative experiment investigating theimpacts of dingo control on dingo ecology (e.g. Allen 2012b;Allen and Leung 2012). This paper uses scat data from thatexperiment to explore spatiotemporal variation in dingo scatcollection rates. Scat collection rates are here defined as the rateat which accumulated scats are collected, which differs fromscat accumulation rates (the rate at which deposited scatsaccumulate) and scat deposition rates (the frequency at whichdingoes defaecate).

Methods

Study sites

The study was conducted on three large cattle stations withinnorthern South Australia during a time of contrasting climaticextremes, from severe drought through to record-breaking rainsand floods (www.bom.gov.au; but see also Allen 2010b).Quinyambie Station is located in the sandy Strzelecki Desert,comprises parallel sand dunes and has a mean annual rainfall of~160mm. Cordillo Downs Station is in the extreme north-east ofSouth Australia inside Haddon Corner, receives a mean annualrainfall of ~167mm, and incorporates both large, irregular sanddunes and extensive stonygibber plains. Todmorden is located onthe sandy Pedirka Desert in the central-north of the state, has amean annual rainfall of ~180mm, and comprises sandy desertsand stony plains. Further information on the location andcharacteristics of the study sites is available elsewhere (e.g. Allenet al. 2011b; Allen 2012a, 2012b; Allen and Leung 2012).

Each of the three stations was divided into dingo-baited andunbaited treatment areas (separated by a buffer zone >20 kmwide at the closest point) as part of the larger experiment. In aregional context (see Allen 2012b for details), Todmorden iswithin the most intensively baited region in northern SouthAustralia, while Cordillo Downs is surrounded by a mosaic ofbaited and unbaited areas. Quinyambie is bordered by the dingobarrier fence, and apart from regular baiting, which occurs insome parts of a narrow buffer zone along the fence, the treatmentareas are surrounded by unbaited areas. The history of lethaldingo control in northern South Australia and details of baitingprograms at each site are given in Allen (2012b).

Scat collection rates

Dingo scats were collected from within each treatment areaduring repeated visits to the stations between May 2008 andAugust 2011.Because of the very high abundance (and thousandsof available scats) of dingoes at Quinyambie (Allen 2012a), scat

collection was restricted to discrete, fenced (to exclude cattle)areas around five permanent artificial livestock watering points(two in unbaited areas, three in baited areas). At the other twosites, scatswere collected fromawide variety of focal point types,such as waterpoints, vehicle tracks, dry creek crossings,intersections and other locations within each treatment areawhere dingoes were expected to defaecate more frequently. Thesame locations within each treatment were surveyed for scats ateach repeated visit to each site. Thus, there was unequal samplingeffort between treatments, but there was equal sampling effortwithin treatments between surveys at each site. Scat collectionrates were calculated as the number of scats collected divided bythe number of days since the last scat collection date. For thefirst survey, the numbers of scats collected were divided by90, assuming that the scats collected represented the previous90 days’ worth of dingo scats accumulated (followingobservations recorded in Wallach et al. 2009).

Results

In total, 4112 scats were collected from Quinyambie (n= 2385),Cordillo Downs (n= 1303) and Todmorden (n= 424) during thestudy period (see also Allen and Leung 2012). Collecting scatsfrom the same areas during repeated visits indicated that scatcollection rates varied substantially between treatments, sites andsurveys independent of dingo control (Fig. 1). For example, atthe commencement of the study at Quinyambie station (i.e.before dingo control had occurred), scat collection rates wereapproximately three times higher in the unbaited treatment thanthey were in the baited area, despite 50% greater samplingeffort in the baited area. This pattern subsequently continuedthroughout most of the study after baiting commenced in thebaited area (Fig. 1). The highest scat collection rate (3.67scats day–1) was recorded at Quinyambie in December 2009;the next highest was 2.30 scats day–1 at Cordillo Downs inNovember 2009 (Fig. 1).

Discussion

Dingo scat collection rates varied substantially betweentreatments and sites (Fig. 1), indicative of spatial variability insuch rates at both fine and broad scales. Scat collection rates alsovaried substantially within treatments between surveys,indicative of temporal variation in such rates. Longer-term trendsin scat collection rates were similar between treatments at eachsite (Fig. 1), suggesting that there was no lasting effect of dingocontrol on dingo scat collection rates. These data supportstudies that likewise show substantial temporal variation in othercommunicative behaviours, such as scratching, howling andurination (Corbett 2001). Assuming, asWallach et al. (2009) did,that scat counts from focal points provide a reliable indicator ofpack structure and stability, these data suggest that dingo packsbecome more stable during drought times (discussed below)and that dingo control has little influence on the stability andstructure of dingo packs in northern South Australia. Thiscontrasts with the conclusions of Wallach et al. (2009), whichmay be related to experimental design issues that weaken thereliability of that study. Such issues included misleading andincorrect background data, invalid comparisons between seasons

138 Australian Journal of Zoology B. L. Allen

and habitats, and unsupported assumptions (Allen 2010a; Allenet al. 2011a; present study).

Interestingly, temporal trends in scat collection rates wereremarkably similar between sites, increasing from early 2008until late 2009 and decreasing through 2010 and 2011 (Fig. 1).Like many parts of Australia, northern South Australiaexperienced increasingly severe dry and windy (i.e. drought)conditions in 2008–09, before receiving record-breaking rainsfrom the summer of 2009–10 right through until early 2011(www.bom.gov.au; but see also Allen 2010b). Data on theabsolute abundance of dingoes at the sites are not availablebut, assuming dingo abundance remained constant throughout

the studyperiod, Fig. 1 suggests that the samenumber of dingoesdepositedmore scats at focal points during drier times and fewerscats at these points when seasonal conditions were favourable.Assuming dingo abundance declined in line with deterioratingenvironmental conditions and increased when the conditionsimproved, Fig. 1 suggests that scat deposition rates at focalpointswere inversely related to dingo abundance.Thedingo scatcollection rates in Fig. 1 would mirror dingo abundance only ifdingo populations increased during the drought and declinedduring flush conditions, which is not likely (Corbett 2001;Allen2010b, 2012b; Allen et al. 2011b;). Alternatively, rain andsubsequent flooding from the summer of 2009–10 onwardsmay

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Fig. 1. Dingo scat collection rates in baited (solid circles) and unbaited (open circles) areas at Quinyambie (top), Cordillo Downs(middle) and Todmorden (bottom) in northern South Australia between March 2008 and August 2011 (approximate baiting datesindicated by arrows).

Dingo scat collection rates Australian Journal of Zoology 139

have washed some scats away, preventing reliable assessmentof relative abundance or social structure from dingo scatcollection rates in some instances. Regardless, scats collectedfrom focal points may not be representative of the widerpopulation because not all individuals from the same packutilise focal points at similar frequencies, even in unbaitedareas (Allen 2012a).

In general support of the research question explored byWallach et al. (2009), however, dingo control is definitelyexpected to have some negative effect on dingo abundance.After all, that is the objective of baiting. But investigatingthe influence of lethal control on the social stability and functionof flexible and adaptable apex predators requires the collectionof more than mere numbers of scats. Because the social status ofindividuals is rarely known and difficult to ascertain, and becausedingo societies have dominance hierarchies that influencethe expression of communicative behaviours (Corbett 2001),researchers will have little ability to attribute a given scat to anindividual or type of individual (e.g. resident or transient,a or b).Social stability is typically assessed through behaviouralobservations of individually identifiable animals, and cannot bededuced from scat data alone (Whitehead 2008).

In summary, substantial spatial and temporal variation indingo scat collection rates was observed (independent of dingocontrol), andwas considered unlikely to reflect dingo abundance.The assumption that dingo scat collection rates vary little overtime was not supported. Thus, conclusions from studies that relyon this assumption may also be unsupported. As concluded byMitchell and Balogh (2007), the data presented here likewiseindicate that the complex and dynamic nature of dingo societiesmaymean that suchcoarse indicesmaynotbe reliable asmeasuresof dingo abundance, social structure or function.

Acknowledgements

I am grateful to all those who helped collect the many dingo scats used in thisstudy in spite of the heat, flies, burrs, sand and smell – your assistance wasgratefully appreciated. The South Australian Arid Lands Natural ResourcesManagement Board administered the state and federal funding (e.g. NationalHeritage Trust and Caring for Our Country) used to undertake much of thisresearch. The Invasive Animals Cooperative Research Centre also providedsome of the resources used to undertake the research and prepare themanuscript.

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