The Ecology of Wild Horses and their Environmental ... - Parks Victoria

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Background Paper 1 of 3The Ecology of Wild Horses and their Environmental Impact in the VictorianAlpsWild horse exclusion plot, Native Cat Flat 2004 (source: Parks Victoria).Parks VictoriaMay 2013This paper was written by: Joanna Axford 1 , Michelle Dawson 2 and Daniel Brown 31 Formerly Parks Victoria, Bright2 Eco Logical Australia3 Parks Victoria, BrightAcknowledgements: Arn Tolsma and Nick Clemann (Arthur Rylah Institute for Environmental Research,DEPI) provided content and reviewed this paper. Charlie Pascoe, Dave Foster and Mike Dower (Parks Victoria)provided information on wild horse impacts in the Alpine National Park, and Malcolm Kennedy (formerly ParksVictoria) reviewed this paper. Joanne Lenehan, PhD candidate (University of New England), providedunpublished results of her study into wild horse impacts in Guy Fawkes River National Park. Alison Matthews(Charles Sturt University), Associate Professor J. Gilkerson (Equine Infectious Disease Laboratory, University ofMelbourne) and H. Crabb (Principal Veterinary Officer-Intensive Farming Systems, DEPI Victoria) wereconsulted on various sections of this paper.

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Acronym ListABA: Australian Brumby AllianceABMA:AALC:AANPs:ANP:BAW:COP:DEPI:Alpine Brumby Management AssociationAustralian Alps Liaison CommitteeAustralian Alps National ParksAlpine National ParkBureau of Animal WelfareCode of PracticeDepartment of Environment and Primary IndustriesEPBC: Environment Protection and Biodiversity Conservation Act 1999FFG: Flora and Fauna Guarantee Act 1988KNP:RSPCA:SOP:VBA:Kosciuszko National ParkRoyal Society for the Prevention of Cruelty to AnimalsStandard Operating ProcedureVictorian Brumby Association

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Table of ContentsIntroduction to Wild Horse Background Papers ..................................................................................... 11. Introduction .................................................................................................................................... 22. Wild horse ecology in the Victorian Alps ........................................................................................ 23.1 Wild horse distribution ........................................................................................................... 23.2 Wild horse population trends ................................................................................................. 33.3 Wild horse demography .......................................................................................................... 63.4 Wild horse social organisation and movement ...................................................................... 63.5 Wild horse habitat and diet preferences ................................................................................ 73.6 Wild horse mortality factors ................................................................................................... 83. Wild horse environmental impacts ................................................................................................. 93.1 Environmental impacts of wild horses .................................................................................... 93.2 Impacts on soil and substrate ............................................................................................... 113.3 Impacts on vegetation .......................................................................................................... 143.4 Impacts on peatlands ............................................................................................................ 183.5 Impacts on waterways (streams and stream-banks) ............................................................ 203.6 Impacts on fauna .................................................................................................................. 224. Wild horse biosecurity issues ........................................................................................................ 255. Gaps in knowledge ........................................................................................................................ 26References ............................................................................................................................................ 27Appendix 1: Officially listed plant ecological communities at risk of severe damage from wild horseactivity ................................................................................................................................................... 36Appendix 2: FFG-listed and EPBC-listed plant species potentially at risk from wild horse activity in theeastern Victorian Alps ........................................................................................................................... 37Appendix 3: Officially listed or threatened fauna species potentially at risk from feral horse activity inthe eastern Victorian Alps ..................................................................................................................... 39

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Introduction to Wild Horse Background PapersHorses (Equus caballus) living in unmanaged, wild populations in Australia are generally known by three terms;feral horses, wild horses and brumbies. Any introduced domestic animal that lives in unmanaged, selfsustaining, wild populations is by definition a feral animal. However, some people are uncomfortable with theterm ‘feral’ being associated with horses and prefer the terms ‘wild horse’ or ‘brumby’. ‘Brumby’ is a colloquialterm often used in Australian folklore; however some people believe the term elicits a romanticised view ofhorses and detracts from their environmental impacts. In this series of papers the term ‘wild horse’ will beused, as it is a generally accepted term and clearly refers to un-domesticated horses living in the wild.Horses were introduced to Australia by early European settlers and Australia now has the highest populationof wild horses in the world, with more than 300 000 (Dobbie et al. 1993). Wild horses are a pest species inAustralia, that is, an “animal that has, or has the potential to have, an adverse economic, environmental orsocial/cultural impact” (Natural Resource Management Ministerial Council 2007).Wild horses occur across the Australian Alps and have been identified as a high priority threat to naturalvalues of the region (Coyne 2001). The “degradation and loss of habitat caused by feral horses” is listed as apotentially threatening process under Victoria’s Flora and Fauna Guarantee Act (1988).In Victoria, wild horses occur within the Victorian Alps, with a smaller population present in the Barmah Forest(Wright et al. 2006). This series of three Background Papers will focus on wild horses in the Victorian Alps(Alpine National Park (ANP) and surrounding State forests).The Background Papers investigate the ecology, environmental impacts, human dimensions and managementand control of wild horses in the Victorian Alps. They are arranged in the following order:Background Paper 1: The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps. The firstsection of this paper considers the ecological dimensions of wild horses in the Victorian Alps including theirdistribution, population trends, demography, habitat, diet and mortality factors. The environmental impacts ofwild horses within the region are then considered including their impacts on: soil and substrate, vegetation,peatlands, waterways and fauna. Biosecurity issues are also discussed.Background Paper 2: The Human Dimensions of Wild Horse Management in the Victorian Alps. This paperprovides the social context for wild horse management in the Victorian Alps. A brief history of wild horses inthe region and the major stakeholder groups involved is outlined. The socio-economic and cultural heritagevalues of wild horses are then explored followed by a discussion on public perceptions about wild horses andtheir management in the Victorian Alps. Research from national and international investigations intoperceptions towards wild horses is drawn upon to help unravel the complexity of this value-laden issue.Background Paper 3: Wild Horse Management and Control Methods. This paper considers the management ofwild horses in the Victorian Alps and considers control methods for managing wild horses. An overview of howwild horses have been managed in the Victorian Alps and the legislation and policy framework for wild horsemanagement is provided. The paper explores welfare issues and costs associated with wild horse control,levels of control and control options.This series of papers was prepared based on available literature and research, and, through consultation withexperts where possible. The papers provide a foundation for discussion concerning the future management ofwild horses within the Victorian Alps.1

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 20131. IntroductionIn Victoria wild horses (Equus caballus) occur in the Victorian Alps with a smaller population present in theBarmah Forest, on the Murray River (Menkhorst 1995; Wright et al. 2006). Wild horses are considered asignificant environmental threat to the Victorian Alps (including the Alpine National Park (ANP) and adjacentState forests). The “degradation and loss of habitat caused by feral horses” is listed as a potentially threateningprocess under Victoria’s Flora and Fauna Guarantee Act (1988). This paper will explore the ecologicaldimensions of wild horses in the Victorian Alps and the extent to which they are affecting the natural values ofthe region.Several studies and reviews have been conducted on the ecology and environmental impacts of wild horses invarious parts of the Australian Alps, including: Dyring 1990; Thiele & Prober 1999a, 1999b; Walter 2002, 2003;Walter & Hone 2003; Montague-Drake 2005; Prober & Thiele 2007; Nimmo & Miller 2007; Laake et al. 2008;Dawson 2005, 2009a, 2009b; and Venn et al. 2009. To help unravel the significance of wild horses in theVictorian Alps, information in this paper is also drawn from national and international literature as well asanecdotal information on wild horses in the Victorian Alps.2. Wild horse ecology in the Victorian Alps3.1 Wild horse distributionWild horses in the Australian Alps are relatively isolated from populations elsewhere in Australia. The largestpopulations in Australia occur in dry and tropical environments, mainly in the Northern Territory andQueensland, but also Western Australia and South Australia (Dobbie et al. 1993). In much of Australia, droughtlimits the distribution of wild horses (Dobbie et al. 1993). However, this is not evident in the Australian Alpswhich occupy wetter bioregions with more consistent rainfall (Hobbs & McIntyre 2005). The distribution ofwild horses in Australia has also been strongly influenced by human intervention including farminginfrastructure such as fencing (McKnight 1976).Wild horses were initially introduced into the Australian Alps by European settlers in the 1830s. Graziersmanaged the distribution (and numbers) of wild horses to varying degrees from the mid-1800s up until cattlegrazing ceased early this century (Walter 2002; Foster 2004). Non-human influences on wild horse distributionin the Alps include preferred habitat, geographical barriers and natural events such as severe snow storms, fireand drought (Walter 2002). Between 1990 (Dyring 1990) and 2002 (Walter 2002) wild horse distributionappeared to be relatively stable in the ANP, however, in the past ten years wild horse populations haveexpanded their range in a number of locations, including spreading to new locations on the Bogong High Plains(Dawson 2009). Dawson (2009) also suggests that there is suitable habitat for wild horses in Australian Alpsthat is currently not occupied. Furthermore, it is predicted that with climate change, areas at higher elevationwill become more suitable for wild horses (Dunlop & Brown 2008; Green & Pickering 2002).The largest population of wild horses in the Victorian Alps is in the eastern Alps (east of Omeo) and isconnected to a population in Kosciuszko National Park, NSW to the north (Figures 1 and 2). It extends south tothe Nunniong Plains, as far west as Mt Pinnibar and Buenba Creek, and to Deddick and Amboyne east of theSnowy River. The second, smaller population is on the southern Bogong High Plains, between Falls Creek andMount Hotham, and in the headwaters of the Cobungra, Bundara and Victoria Rivers (Ethos NRM 2012). TheBogong High Plains/Cobungra population is isolated from the Eastern Alps population by around 30km andconsidered to have a lower density of horses than the east Alps population (Ethos NRM 2012) (figure 2). Bothpopulations, while situated predominantly within the ANP, extend into adjacent State forests and reservesand, probably, private land.2

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Records of small groups of horses have occurred at other disjunct locations across the Victorian Alps from timeto time, however these isolated records are considered not represent extant populations.In spring 2009 a group of 18 wild horses was discovered in the headwaters of the Moroka River, near MtWellington in the Alpine National Park and the adjacent Carey State Forest. This group of horses is suspectedto have been illegally introduced, but was gradually trapped and removed by Parks Victoria and DEPI over thesubsequent summer and autumn. In early winter 2010, another new group was discovered in State forest atConnors Plain, north-west of Licola. This group was also trapped and removed. Monitoring continues in bothareas to ensure that all the horses have been captured.Mount BuffaloNational ParkAlpine National ParkAlpine National ParkAlpine National ParkSnowy RiverNational ParkFigure 1: Estimated wild horse distribution in the Victorian Alps, showing the two disjunct populations. This distributionmap is based on a report by Ethos NRM (2012) that used previous horse records and interviews with a broad range ofstakeholders (with knowledge and experience of wild horses in the Victorian Alps) to estimate the distribution of wildhorses in the Victorian Alps. NB: This map is based on anecdotal qualitative information and provides only a broad guide towild horse distribution.3.2 Wild horse population trendsThe most reliable estimates of wild horse population size have come from aerial surveys across the AustralianAlps National Parks (AANPs) conducted in 2001, 2003 and 2009 (Walter & Hone 2003; Dawson 2009). Thesesurveys were developed with the aim of providing a repeatable and robust method for monitoring wild horsepopulation size in parts of the AANPs (not including adjacent areas such as State forests and private land)(Walter & Hone 2003). Surveys are conducted from a helicopter at a fixed-height and speed along east-westtransects at two kilometre intervals and analysed using line-transect techniques (Walter & Hone 2003). Thismethod was designed to minimise several potential sources of bias such as decreasing detectability of horseswith distance from the aircraft (Walter & Hone 2003), and counting horses more than once (see Linklater &Cameron 2002).3

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013140120Estimated Horse PopulationHorses Removed100Number of Horses8060405537 383120010116792 95 88 512005 2006 2007 2008 2009 2010 2011 2012YearFigure 4: Estimates of wild horse population size ± SE for the Bogong High Plains population only. The number of horsesremoved from these areas by Parks Victoria since 2005 is also included (red columns). Population estimates are derivedfrom aerial surveys (Dawson and Miller 2008).3.3 Wild horse demographyWild horses have an annual breeding season, producing one young at a time (Grange et al. 2009). The firstyoung are usually produced when females are three years of age. When wild horse density is low and food isabundant they occasionally reproduce at two years of age (Berger 1986; Duncan 1992). During a three yearstudy from 1999 to 2002, the youngest mare observed with a foal in the Australian Alps was three years old(Dawson & Hone 2012). Foaling rates increase up to the age of five and mares continue to have high foalingrates until the onset of senescence at 15-18 years of age (Garrott & Taylor 1990; Garrott et al. 1991b; Duncan1992; Linklater et al. 2004; Grange et al. 2009). Foals are usually born in the summer months when foodavailability is at its highest (after an 11 month gestation) but can be born at any time of year (Dawsonunpublished data). Foaling rates observed for wild horses in three separate populations in the Australian Alpsbetween 1999 and 2002 were lower than those reported in other environments with 42-62% of adult femalesobserved with foals (Dawson & Hone 2012).Between 1999 and 2002 survival rates of adult wild horses in the Australian Alps were generally high (91% perannum) with little annual variation, while survival rates in the first three years of life are lower and morevariable (63-75% per annum) (Dawson & Hone 2012). This is similar to wild horse populations from around theworld (Garrott & Taylor 1990; Linklater et al. 2004; Grange et al. 2009; Scorolli & Lopez Cazorla 2010). There isno data on the lifespan of wild horses in the Australian Alps, however studies of wild horses in Maryland,United States of America (USA) found wild horses lived as long as 20 years (Kirkpatrick & Turner 2008).3.4 Wild horse social organisation and movementWild horses live in small social units as harem or bachelor groups. Harem groups consist of a dominant male,multiple females and their off-spring (Menkhorst 1995). Bachelors are non-dominant males that have been6

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013forced out of their harems; they generally occur alone or in groups of two or three (Dobbie et al. 1993). Theaverage group size (harem and bachelor groups) from three sites across the Australian Alps was 5.65 (± 0.51SE) (Walter & Hone 2003), while Drying (1990) found that harem group sizes in the Alpine region ranged fromtwo to 11 individuals, with groups typically consisting of one stallion, two mares and one foal. Wild horsesrarely have periods of social isolation during their lifetime except for bachelors in their pre-harem formationstage (van Dierendonck 2006). Harem groups tend to be stable breeding units and generally favour permanentlocations around reliable water sources (Dobbie et al. 1993). Within harem groups, adult mares form a longtermstable nucleus, while the breeding stallion is regularly replaced (van Dierendonck 2006). Bachelor groupsare more mobile and unstable (Dobbie et al. 1993).Groups of wild horses are loyal to undefended home ranges with central core use areas (Linklater 2000). Thehome ranges of groups overlap entirely with other groups and home range size increases with group size(Linklater 2000). Home ranges of wild horses in the Australian Alps have not been studied but there isinformation available from other environments. Home range sizes vary within a region and between regions. InQueensland and central Australia wild horses were estimated to have a home range of approximately 100km²and 70km² respectively (Dobbie et al. 1993). In contrast, wild horses at Kiamanawa in New Zealand, which hasa similar climate to the Australian Alps, had home ranges 0.96 to 17.7 km 2 (Linklater 2000). Given the climaticsimilarities, home range of horses in the Victorian Alps are likely to be similar to Kaimanawa.As prey animals in their native environment, a horse’s primary defence mechanism is rapid flight away fromthe threat of danger. It is therefore advantageous that they identify potential predators as quickly as possible(van Dierendonck 2006). This is aided by their monocular and binocular vision, which enables them to have anextensive view of their surrounds (Dobbie et al. 1993). With well developed hearing any movement is readilydetected (Dobbie et al. 1993).3.5 Wild horse habitat and diet preferencesWild horses occupy a range of habitats across Australia and the world. While they are best adapted to opengrassy plains they will also use rugged country (Norris & Low 2005). Wild horses are present from the highestto the lowest elevations in the Australian Alps (Walter 2002). Some groups may migrate to lower elevations inwinter but many horses maintain a high elevation (1600 metres) home range throughout winter (Dawson,unpublished data). Drying (1990) found that wild horses in Kosciuszko National Park (at a site in NSW sixkilometres from the Victorian border) made extensive use of heaths and grasslands for feeding, whilstavoiding the forests at all times of the year; this preference for open areas was broad-based with nodiscrimination between feeding and other activities. The preference for grasslands over forest is universal forwild horses (Pratt et al. 1986; Keiper & Berger 1982; Berger 1986; Linklater et al. 2000). The only exceptionhas been observed in the middle of the day in summer when wild horses seek refuge from the heat andhorseflies (Tabanidae) in forested areas (Duncan 1983; Dyring 1990; Keiper & Berger 1982; Berger 1986).Wild horses spend most (55-65%) of their time feeding (Duncan 1980). They are generalist grazers with astrong preference for the greatest concentrations of high quality food (green plant matter); when green plantmatter becomes sparse, the horses’ tactic is to search out areas with the greatest concentrations of perennialherbaceous plants, green or dead (Duncan 1983). Their diet mainly includes herbaceous plants (grasses, reeds,sedges and forbs), but they will also eat roots, bark, buds and fruit (Csurhes et al. 2009). Due to their forwardcutfront incisors they are able to graze close to the ground (Dobbie et al. 1993). Horses have a differentdigestive system to most ungulates (hoofed mammals), which enables them to consume large quantities oflow quality food and survive on a lower quality diet than cattle (Janis 2007). Cattle require time to chew theircud so cannot consume such large quantities but tend to select higher quality food (Janis 2007).Horses must drink at least once a day in summer and at least every second day during winter (Norris & Low2005). If food is plentiful horses will graze near water sources (Dobbie et al. 1993).7

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 20133.6 Wild horse mortality factorsWith few predators, unmanaged wild horse populations may increase in size and distribution until theyapproach carrying-capacity; at this point the population size stabilises as a result of a decrease in birth ratesand survival rates caused by limited food availability (Grange et al. 2009; Scorolli & Lopez Cazorla 2010). Forexample, in the Camargue in France, Grange et al. (2009) found that a decrease in available food resources, asa result of increasing density, caused a loss of body condition and the survival of foals and adult femalesdecreased with increasing density.In sub-alpine and montane environments of the Australian Alps, there is evidence that between 1999 and2002, the growth of three wild horse populations was limited by food availability (Dawson & Hone 2012). Thedensity of horses at the three sites was higher than the average determined from aerial surveys (see above).The Cowombat wild horse population had the highest density (6.4 km²), adult horses had the poorestcondition, recruitment (from birth to 3-years-old) was low, pasture biomass was low and population growthwas zero. In general however, unlike the Camargue example above, wild horses in the Australian Alps are notcontained and do not currently occupy their entire potential range (Dawson 2009). Therefore there is scopefor the wild horse population to spread.It is not clear whether wild horse populations across the Australian Alps would reach ‘carrying capacity’because the ability to reach equilibrium density depends on the variability of environmental conditions. Instochastic environments characterised by a high degree of unpredictable environmental variance (e.g. rainfall),an equilibrium is not reached (McLeod 1997). There are several examples of environmental events, inparticular drought, snow and fire, which have lead to dramatic declines in wild horse populations (thuspreventing the population from reaching carrying capacity). The eastern side of the AANPs (e.g. Buchan River,Lower Snowy, Suggan Buggan) lies in a rain-shadow and has limited available water. The drought in 1982-83was reported to have led to a dramatic decline of most wild horses in this area (Walter 2002), similar patternsare observed in central Australia (Dobbie et al. 1993). Drought can affect horses through thirst, starvation andingestion of poisonous plants (Dobbie et al. 1993).At higher elevations wild horse mortality occurs as a result of severe snow events or long periods of snowcover in the alpine area (Walter 2002). In winter wild horses at higher elevations, such as those on the BogongHigh Plains, have to dig through snow to access food for many weeks of the year which leads to a loss of bodycondition in the horses (Dawson unpublished data). In some cases severe snow events have resulted inmortality and in one historic event in the Brindabella’s (Australian Capital Territory (ACT)) an entire populationwas wiped out (Walter 2002).The 2003 fires had a substantial impact on the wild horse population of the Australian Alps, with a sharpdecrease in the wild horse population size following the fires (Figure 2). After the fires, Walter (2003) indicatedthat when wild horse numbers were low, that there was great potential for the population to increasedramatically due to the increased availability of high quality food and reduced population pressure. This wasdemonstrated by the results of the 2009 aerial survey which showed that the population had increased by224% since 2003 (Dawson 2009a). In a slightly different context, Catling (1991) predicted that wild horseswould be advantaged by frequent low intensity fires due to a simplification in forest structure.Additional wild horse mortality factors that should be considered include wild dogs and parasitism. There havebeen reports of wild dogs chasing foals in the Victorian Alps (Walter 2002). Parasitism and disease may also becauses of mortality and/or reduced health. However, neither of these factors has been formally investigated orquantified.8

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 20133. Wild horse environmental impacts3.1 Environmental impacts of wild horsesAustralia's ecosystems have evolved without the grazing pressure and the physical impact of heavy, hardhoofedanimals (Carr & Turner 1959a; 1959b Ashton & Williams 1989; Green et al. 2006). Wild horse activity inthe Victorian Alps represents a type and intensity of impact to which native ecosystems and their componentsare not adapted. The environmental impacts of wild horses are recognised by Victoria’s environmentlegislation with “degradation and loss of habitat caused by feral horses” listed as a threatening process underthe Flora and Fauna Guarantee Act (1988).The social and behavioural habits of wild horses as well as their physical characteristics (i.e. hard hooves, largesize, dietary preferences and general requirements), impact on the environment directly and indirectly.Trampling and grazing are the most researched and known agents of change associated with wild horses (Loydi& Zalba 2009). However, other negative actions include: consumption of native plants, bark chewing,compaction of soils, pugging (trampling of wet soils leaving a dense mat of deep footprints), track formation,wallowing (rolling), and the redistribution of nutrients and plant seeds via dung and urine. The impacts ofthese actions are summarised in Table 1.Table 1: Summary of wild horse environmental impactsElement Impacts Australian Alps research General researchSoil & substrate • Exposed soil surface;Dyring 1990Berman & Jarman 1998• soil loss & erosion;Whinam et al. 1994 Beever & Herrick 2006• down-slope sedimentation;De Stoppelaire et al. 2004• soil pugging, drying & compaction;Rogers 1991, 1994• loss of soil structural compositionTurner 1987especially on wet soils; &Loydi & Zalba 2009• creation of nutrient hotspots(especially nitrogen).Peatlands (alsoknown as bogs ormossbeds)Waterways(streams &streambanks)Vegetation (&communities)• Drying out of bogs & potentialdraining of entire bog systems;• creation of bare pavements;• incision & soil erosion;• silt deposition downstream;• dominance of unpalatable species; &• loss of habitat for threatenedspecies.• Degradation of stream function;• incision & channelling;• soil compaction leading to decreasedinfiltration;• increased downslope sedimentation;• increased nutrient loads;• lateral erosion;• streambank disturbance & slumping;• fouling of waterholes; &• changes in water flow & drainagepatterns.• Removal of native vegetation cover;• dispersal of weed seeds;• changes to the vegetation structure& species composition of the groundstratum;• native tree mortality;• increase vulnerability of threatenedvegetation; &• increased nutrient loads.Dyring 1990Whinam & Chilcott 2002Whinam et al. 2003Tolsma 2008a, 2008bProber & Thiele 2007Dyring 1990Whinam & Comfort 1996Whinam & Chilcott 2002Prober & Theile 2007Wild & Poll 2012Dyring 1990Whinam & Chilcott 2002Whinam & Comfort 1996Whinam et al. 1994Prober & Theile 2007Walter 2002McKay 2001Leigh et al. 1991Thomas 2010Wild & Poll 2012Rogers 1991, 1994Beever & Brussard 2000Rogers 1991, 1994Beever & Brussard 2000Beever et al. 2003Beever et al. 2008Rogers 1991, 1994Turner 1987Loydi & Zalba 2009De Stoppelaire et al. 2004Bridle & Kirkpatrick 1999Cambell & Gibson 2001Schott 20029

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Native fauna • Competition for resources;• altered food availability;• habitat modification & loss;• increased vulnerability of threatenedspecies; &• competitive exclusion.Clemann et al. 2001Clemann 2002Brown et al. 2007Berman & Jarman 1998Lenehan 2010Zalba & Cossani 2009Beever & Herrick 2006Beever et al. 2008Nano et al 2003The degree of wild horse related degradation in the Victorian Alps will depend on:• wild horse density;• scale of activity (extent);• topography – including slope;• elevation;• climate;• recent weather;• local drainage;• access to suitable areas;• timing (i.e. seasonality of grazing);• the resilience of the vegetation community;• soil type (i.e. fineness and/or wetness);• the frequency and intensity of use;• effects of other sympatric species; and• the longer-term disturbance history of the site (Whinam etal. 1994; Beever et al. 2003; Beever et al. 2008).These factors vary throughout the Victorian Alps but some generalisations can be made.Concerns about the environmental impacts of wild horses in the Australian Alps were first raised in the 1950s(Costin 1954). While there is extensive evidence of wild horse impacts in the Victorian Alps, relatively fewstudies have been undertaken to quantify these impacts. Research includes:• Dyring (1990) conducted research on the effects of wild horses on sub-alpine and montaneenvironments in Australia. Wild horse impacts on soils, vegetation and streams were quantified infour small catchments in the southern Snowy Mountains. Seasonal habitat usage and the abundanceof wild horses were also investigated. Wild horses were found to either initiate or perpetuate changesin sub-alpine and montane environments. Rates of environmental change could not however beinvestigated in the short time-frame of the study.• In 1999 an experimental program was established in the East Alps Unit of the ANP to determine theeffects of wild horse activity on grasslands and stream margins (Prober & Thiele 2007; Wild and Poll2012). Exclosure plots, that prevent horses from accessing a defined area but allow access for otheranimals, were established at Cowombat Flat and Native Cat Flat. Detailed vegetation monitoring ofthese exclosure plots, as well as monitoring of stream bank condition, disturbance and erosion wasundertaken in 1999, 2005 and 2012 (Prober & Thiele 2007; Wild and Poll 2012). The results show thatchanges to stream structure and function as a result of wild horses are clear and substantial, withsignificantly more incision and damage in the wild horse occupied area (outside the wild horseexclosures). Exclosure from horses has led to clear increases in vegetation height and increased littercover (Wild and Poll 2012). The effect of wild horses on vegetation structure and composition wasless consistent; however there was a trend for the recovery of dense swards of sedges and grassesassociated with the competitive exclusion of some lower stature species inside horse exclosures (Wildand Poll 2012). In contrast, horse occupied areas tended to be characterised by low herbfield turfs,likely to be maintained by the preferential grazing of grasses and sedges by horses (ibid).• In 2008 Arn Tolsma from the Arthur Rylah Institute assessed the status and needs of 105 individualmossbeds (also commonly termed peatlands or bogs) in the Victorian Alps (Tolsma 2008a; 2008b).This work supplemented broad-scale post-fire assessment of mossbeds that have been conducted bythe Arthur Rylah Institute since 2004. The aims included: to assess the current state of sub-alpinemossbed communities, estimate potential threats to mossbeds and determine restoration and othermanagement needs. Tolsma found that most systems show signs of contraction over a decadal scale,and few systems could be considered in relatively good condition. Evidence of wild horse activity10

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013(tracks, compaction, trampling, pugging and stream bank slumping) was observed in 67% (70 of 104)of the mossbeds assessed that year. Tolsma argued that on-going activity by wild horses is of greatconcern in the east Alps of Victoria. In the East Alps Unit of the ANP, 97% (63 of 65) of peatlandsystems were found to be impacted (i.e. compacted, trampled or pugged) by wild horses (Tolsma2008b).• In 2011 the AALC commenced a project that aims to quantify the impacts of wild horses on uplandstreams and wetlands in the Australian Alps. The results of this study will be available in autumn 2013and will provide further evidence of the impacts of wild horses on sensitive environments.A number of protected areas regionally, nationally and internationally recognise that wild horses have anegative impact on the environment and have developed strategies to address these impacts (Table 2).Table 2: Examples of wild horse management plans and strategies and their ecological rationaleRegion Wild horse strategy Rationale for the plan (ecological)AANPsNationalNewZealandKosciuszko National Park HorseManagement Plan.Namadgi National Park Feral horseManagement Plan.Guy Fawkes River National Park:Horse Management Plan.Feral horse Management Plan forOxley Wild Rivers National ParkProtecting the natural & culturalvalues of Carnavon National Park:A plan to manage wild horses &other pest animalsKaimanawa Wild Horses Plan.The National Parks & Wildlife Service has legislative responsibility toprotect native habitats & wildlife within its reserves & a responsibilityto minimise the impact of introduced species, including wild horses.The 2006 Plan of Management called for a wild horse managementplan & the exclusion of wild horses from key areas. (NSW NPWS 2008).The plan aims to minimise the negative impact of wild horses includinggrazing on sensitive vegetation, trampling of streambanks, trailformation & erosion. These can lead to draining of entire bog systems,loss of habitat for threatened species & silt deposition downstream.(ACT Government 2007).The National Parks & Wildlife Service has legislative responsibility toprotect native habitats & wildlife within its reserves & a responsibilityto minimise the impact of introduced species, including wild horses(NSW NPWS 2006a). Wild horses are an introduced species that haveadverse impacts on Australian ecosystems with particularly severeconsequences for native fauna & flora (English 2001).Wild horses have been identified as posing a threat to the conservationvalues of the park & water quality. (NSW NPWS 2006b).Queensland Parks & Wildlife Service has a legal obligation to conserve& protect the natural values of Canarvon NP & control threateningprocesses caused by pest species including wild horses. Destructiveimpacts by wild horses have led to: the deterioration of aquaticecosystems & serious landscape dysfunction (losses in biomass,accelerated erosion, soil compaction, altered species composition &vegetation structure & altered fire ecology). (Weaver 2007).Horses have been shown to adversely affect nationally significantecological values. There is a need to eliminate the impacts of horses onimportant conservation values. (DOC 2006).In addition to these wild horse plans and strategies, a series of workshops on wild horse impact andmanagement in the Australian Alps (see: Walters & Hallam 1993; O’Brien & Solomon 2004) and a nationalworkshop (see: Dawson et al. 2006) have demonstrated widespread concern from scientists and practitionersabout the impacts of wild horses in alpine and sub-alpine environments.The impacts that wild horses have on the soils and substrate, peatlands , waterways, vegetation and fauna ofthe Victorian Alps is considered below in greater detail.3.2 Impacts on soil and substrateIt is generally accepted that alpine areas are more susceptible to damage by hard hooved animals such as wildhorses than most other environments, due to their wet fragile soils and slow vegetation growth rates (Whinamet al. 1994). Wild horse trampling and grazing can lead to major changes to the soil, including: pugging, drying,11

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013compaction and erosion (Berman & Jarman 1988; Dyring 1990; Beever & Herrick 2006; De Stoppelaire et al.2004).Some of the immediate effects of wild horses include the creation of tracks and bare patches due to trampling,wallowing and horse camps (see Photo 1, 2 and 3). Trampling and wallowing have been found to causelocalised damage by reducing organic matter and exposing and compacting the soil surface (Dyring 1990).Track networks are formed by the movement of wild horses. Dyring (1990) found that wild horses produceextensive track networks in the Australian Alps. Continual trampling by wild horses can increase soilcompaction and therefore reduce aeration and pore space of soils and subsequently decrease waterinfiltration and moisture content of soils. In addition, trampling and wallowing reduce plant cover and diversity(Dyring 1990). The loss of vegetation cover means a reduction in shading for soils and less organic matterinputs, resulting in greater erosion and a reduced ability of the soil to retain moisture (Beever & Herrick 2006).Beever and Herrick (2006) found in western Great Basin sites (USA), three to 15 times lower penetrationresistance (a measure of soil compaction) in the soil surfaces of sites without wild horses (compared to thosewith wild horses).Photo 1: Trampled area at Cowombat Flat (source: Arn Tolsma 2008).Photo 2: Wild horse camp, Davies Plain (Source: Arn Tolsma 2008)12

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Photo 3: Trampling at The Playgrounds, ANP (Source: Arn Tolsma 2008)In the Australian Alps wild horse tracks have been found to result in a loss of plant cover, erosion (averagingbetween 40-156cm³/m²), soil compaction, and a loss of soil structural composition (Dyring 1990). Drying(1990) found that the soil on tracks was significantly compacted compared with off-track areas. Compactionwas found to be most severe on dry soils, where 20-50 passes by wild horses resulted in significantlycompacted soils. Compaction was found not to increase substantially with subsequent passes. Therefore anaverage group of four wild horses using a new track twice daily for less than a week will result in significantcompaction. Wild horses were found to have similar usage of sub-alpine and montane areas, with nodifference in compaction or track width demonstrated between these sites (Dyring 1990). Whinam et al.(1994) in their study of horse riding in Tasmanian Alpine environments found that 20-30 passes by horses hassubstantial immediate as well as delayed effects on the soils of shrubland, herbfield and bolster heathcommunities, however effects on dry grassland soils were less evident. Wild horse exclosure experiments inthe eastern Victorian Alps have shown that continued grazing and trampling by wild horses has maintained lowherbfield turfs, where the soil surface is more susceptible to trampling impacts than the grasslands found inthe horse exclosure plots (Wild & Poll 2012; Whinam et al. 1994).Dyring (1990) found that wet soils were less prone to compaction but more susceptible to structural damagethan dry soils. This is supported by Rogers (1994) who demonstrated that dry areas are more resistant tofracturing than wet areas, which were more easily broken up by trampling. The loss of soil structuralcomposition is most pronounced on wet soils because horse trampling and grazing fractures saturated soils(Rogers 1994; Turner 1987; Dyring 1990). Fracturing of water saturated grassland can result in downslopesedimentation, water ponding, and opportunities for the establishment of weeds (Rogers 1994). The gradientof the slope has been found in other studies to directly correspond to the level of erosion. The steeper theslope the more prone it will be to erosion (Dyring 1990).Disturbances to the substrate caused by actions such as wild horse trampling, wallowing and grazing increasethe exposure of soils to the elements (such as wind, rain and needle ice), leads to the removal of vegetationand alters drainage conditions hence increasing susceptibility to erosion (Dyring 1990). In central Australia,wild horses were linked to aggravated gully erosion in areas close to water (Berman & Jarman 1988). Wildhorses caused considerable erosion in a sandy environment in the USA: over a five to seven year period fencedplots (excluding horses) were on average 0.63 m higher than unfenced plots in sand dunes habitats (DeStoppelaire et al. 2004).Pugging of soil (trampling of wet soils leaving a dense mat of deep footprints), in particular around wetlandsand waterways, can change soil nutrient status, and increase water turbidity and sediment loads in adjacentwaterways (O’Connor 2005). Dyring (1990) found that wild horses in the Australian Alps can create nutrient13

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013hotspots due to the high levels of nutrients (especially nitrogen) in their dung and urine. Manure in dung pilesincreases the availability of soil nutrients, especially nitrogen and phosphorous, thus creating microhabitatssuitable for weed invasion (Loydi & Zalba 2009).3.3 Impacts on vegetationThe level of impact wild horses have on native vegetation is dependent on the amount and type of use, and,the resilience of the vegetation (Whinam et al. 1994). The most obvious impact wild horses have on vegetationis a reduction in vegetation cover and height, however they may also alter plant species composition, richnessand diversity, and contribute to weed invasion (Turner 1987; Dyring 1990; Rogers 1991; Beever & Brussard2000; De Stoppelaire et al. 2004; Loydi & Zalba 2008; Wild and Poll 2012). Trampling by wild horses also altersvegetation, particularly along tracks and at watering points (Turner 1987; Dyring 1990; Rogers 1991; Beever &Brussard 2000).3.3.1 Removal of native vegetation by grazing, trampling and wallowingVertebrate grazers can negatively affect the cover of herbs in alpine and subalpine regions of Australia (Bridle& Kirkpatrick 2001). Dyring (1990) found that wild horses preferentially graze grasslands and healthlands.Studies in the greater alpine region have demonstrated that a decrease in grazing pressure from introducedherbivores has led to an increase in plant cover or flower stem production (Carr & Turner 1959a; 1959b;Wimbush & Costin 1979a; 1979b; 1979c; Leigh et al. 1991; Wahren et al. 1994). Bridle and Kirkpatrick (2001) intheir study of Tasmanian alpine and subalpine plains found the impacts of domestic stock (i.e. cows, horses,sheep), rabbits and native herbivores on treeless subalpine vegetation were much greater than the effects ofnatives herbivores and rabbits alone (Bridle & Kirkpatrick 1999).McKay (2001) conducted a survey of the impacts of horse-riding and walking on the alpine vegetation ofMount Bogong. Trampling was found to reduce the height, cover and abundance of both shrub and groundflora within track areas and to result in greater exposure of bare ground. Beever et al. (2008) argue that theloss of connectivity in shrub canopy due to rubbing and trampling may increase rates of isolation,evapotranspiration and soil loss at small spatial scales.Results from the Cowombat Flat and Native Cat Flat horse exclosure plot monitoring program have shown thathorse trampling and grazing has resulted in the removal of vegetation and increased bare ground in horseoccupied areas (Wild & Poll 2012). In contrast, fenced horse exclosure plots showed a trend for increasingvegetation cover and decreasing bare ground as they recovered from past horse disturbance over a thirteenyear period (ibid).It is argued that grazing may have an impact on the reproductive success of some flora species by impacting onthe dispersal opportunities of wind-dispersed species as well as their ability to attract pollinators; both ofthese functions are affected by flower height (Bridle & Kirkpatrick 1999). For example, on the AssateagueBarrier Island (USA), a small herbaceous annual, Amaranthus pumilus was once abundant and is now limited toa couple of individuals; its decline is linked to wild horse grazing and trampling (De Stoppelaire et al. 2004).Bridle and Kirkpatrick (1999) found decreased fecundity of herbs with increasing grazing pressures. InAustralia, clipping experiments on alpine herbs have shown that flowering success may be retarded if plantsare clipped early in the growing season or if they are cut more than once (Leigh et al. 1991).3.3.2 Change in vegetation composition and structureGrazing by introduced herbivores can alter the appearance, productivity and composition of vegetationcommunities (Dyring 1990; Hobbs & Hyeneke 1992). This may be due to reduced regeneration/recruitment asa direct result of selective grazing or the physical impacts of trampling and erosion. Wild horses selectivelygraze palatable species and have the potential to change the composition of threatened vegetation14

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013communities (Dyring 1990). Redistribution of nutrients through dung can also contribute to the changes invegetation patterns (Dyring 1990).Trampling can create openings in vegetation that provide opportunities for new plants to become established.Different vegetation types demonstrate differing levels of resistance (tolerance) to trampling. Within some,non-tolerant vegetation types, trampling can slow the growth of dominant species sufficiently to allow thepersistence of less vigorous species (Hobbs & Hyeneke 1992).Dyring (1990) found trampled sites (and areas adjacent to track systems) had lower native plant diversity and ahigher abundance of exotic species. Plants found on wild horse tracks were characteristically non-woodyprostrate fast-growing annuals and grasses, with hemicryptophitic life-forms (species with renewal buds nearthe surface), which tolerated trampling better than upright plants (Dyring 1990). Similarly, horse occupied sitesat Cowombat Flat and Native Cat Flat exhibited a predominance of hemicryptophitic species in contrast tohorse exclosure plots, which were dominated by grasses and sedges (Wild & Poll 2012). Grasslands are moreresilient to the impact of wild horses than other communities where ferns, mosses and shrubs are importantcomponents of the vegetation (Whinam et al. 1994; Venn et al. 2009). Whinam and Chilott (1999) found thatshrubs and shrubland communities were more vulnerable to trampling than other life-forms or vegetationtypes in central Tasmanian alpine vegetation.As well as affecting vegetation community composition, wild horse activity can affect the physical structure ofvegetation communities. Exclosure experiments have shown that vegetation cover and height is far greater inhorse free sites (Turner 1987; Beever & Brussard 2000; De Stoppelaire et al. 2004; Prober & Theile 2007; Wild& Poll 2012). Lower plant biomass was found in the Australian Alps where wild horse densities were higher(Walter 2002). In the Cowombat Flat and Native Cat Flat wild horse exclosure plot monitoring program, thefollowing results occurred in the wild horse exclosures (see also Photo 4):• a significant increase in the average height of vegetation;• a significant increase in litter cover;• no significant effect in species richness at Cowombat Flat;• significantly lower native species richness at Native Cat Flat, due to the gradual competitive exclusionof some lower stature species by dense swords of sedges and grasses;• no indication of an increase in weed richness/abundance due to exclosure (Prober & Theile 2007,Wild & Poll 2012).While the effect of wild horses on vegetation structure and composition was less consistent than the effect ofhorses on vegetation height, plots inside horse exclosures were often characterised by dense swards of sedgesand grasses associated with the competitive exclusion of some lower stature species (Wild & Poll 2012). Incontrast, horse occupied areas tended to be characterised by low herbfield turfs, likely to be maintained bythe preferential grazing of grasses and sedges by horses (ibid). Wild and Poll (2012) suggest that theresurgence of dense sedges and grasses and competitive exclusion of some lower stature species may indicaterestoration to a previous, more natural state and possibly towards a peatland environment.Studies in the USA have shown that wild horses can lower vegetation cover, abundance and flora speciesrichness as well as alter the species composition and structure of the vegetation (by increasing thepredominance of grazing resistant forbs and exotic plants and creating a less continuous shrub canopy)(Beever et al. 2003; Beever and Herrick 2006; Stoppelaire et al. 2004; Beever & Brussard 2000). Using a seriesof monitoring and exclosure plots in the Kaimanawa Mountains, New Zealand, Rogers (1991; 1994), found thatwild horses severely disrupted the composition of the native vegetation. In the grazed plots, species biomassand stature was low for all potentially taller, palatable grasses (Rogers 1991).15

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Photo 4: Cowombat Flat wild horse exclusion plots from the air (source: Geoff Robinson).3.3.3 Threatened vegetationIn the Victorian Alps, wild horses are considered to be one of the major threats to alpine ecosystems (Tolsma2008b). Wild horses are considered to be a serious threat to at least five plant communities listed in theVictorian Flora and Fauna Guarantee Act 1988 (FFG) (Appendix 1), and numerous plant species (Appendix 2).The threat that wild horses pose to threatened species and communities is recognised in the listing of“degradation and loss of habitats caused by wild horses” as a potentially threatening process under the FFGAct. It is likely that wild horses threaten many other species or communities not yet identified or investigated.Trampling by ungulates (hoofed animals) has been considered one of the major threats to several FFG listedalpine vegetation communities. Within the Caltha introloba Herbland Community, cushions of tuft-rush(Oreobolus), which play an important role in reducing the erosive forces of flowing water, may be dislodged bytrampling, or their regeneration disrupted (McDougall 1982; McDougall & Walsh 2007). Similarly, the AlpineSnowpatch Community, situated on steep sheltered slopes, is subject to constant irrigation during the thawwhich renders them particularly susceptible to soil loss following damage to the vegetation by trampling(McDougall 1982; Wahren et al. 2001a; McDougall & Walsh 2007). Montane Swamp, because of its position inthe landscape, is another listed community likely to be susceptible to the impact of wild horses (Dawson 2009).Ecological communities which have been listed under the Federal Environment Protection and BiodiversityConservation Act 1999 (EPBC) and/or the Victorian FFG Act 1988, and that are potentially at risk from wildhorses, are presented in Appendix 2.In order to mitigate the threat that wild horses pose to threatened flora species in the Victorian Alps, ParksVictoria has established three wild horse exclusion fences around particularly threatened and sensitive16

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013communities. In 2002 two wild horse exclusion fences were established on Davies Plain around sub-alpinebogs known to contain several threatened plant species and the threatened Alpine Water Skink. In 2010 anexclusion fence was established at The Playgrounds to protect a population of threatened Marsh Leek Orchid(Prasophyllum niphopedium) (see Photo 5). The aim of all exclusion fences is to protect these species (and theirhabitat in the case of the Alpine Water Skink) from trampling and grazing by wild horses.Photo 5: The Playgrounds wild horse exclusion fence, established to protect a population of threatened Marsh Leek Orchid,an alpine bog community and habitat for the endangered Alpine Water Skink (source: Parks Victoria 2012).3.3.4 Weed dispersal and encouragementWild horses can facilitate weed invasion through dispersal and the creation of a favourable environment forweeds through disturbance. Weed species are dispersed through attachment to the body of the wild horse(epizoochory) or by being ingested and later excreted (endozoochory) (Cambell & Gibson 2001). Thereforewild horses have the potential to disperse weeds both long and short distances and can subsequentlycontribute to the establishment of weed species across several spatial scales (Nimmo & Miller 2007). Weaverand Adams (1996) argue that within their home range, horses are a potentially significant vector in thedispersal of a range of weed species.While wild horses are less likely than domestic horses (i.e. recreational riding horses or horses illegally releasedinto the region) to introduce new weeds into the Victorian Alps, there is potential for this to occur, especiallyconsidering their increasing range and the potential for wild horses to occur across tenures (i.e. farms, stateforests and national park). Many species of seed are transported in the dung of wild horses. Dung can be asource of viable seed taxa not otherwise found in a community (Campbell & Gibson 2001). Campbell andGibson (2001) found that horses pass large numbers of seeds through their digestive tract generally within48hours of consumption (but sometimes longer), and many of these seeds remain viable (Weaver & Adams1996). In some cases the process of digestion scarifies the seed coat, enhancing germination (Campbell &Gibson 2001). Weaver and Adams (1996) investigated the spread of environmental weeds into areas of nativevegetation along horse-riding tracks in three national parks in Victoria (including the ANP). Twenty-ninespecies of weeds were found to be dispersed via horse manure.Wild horse disturbance (i.e. dung, soil disturbance and pugging) can provide favourable environmentalconditions for the germination and colonisation of weed species (Dyring 1990; Rogers 1991; Loydi & Zalba2009). Wild horse dung can result in significant changes in vegetation and can introduce and encourage someinvasive weed species that could eventually colonise more pristine areas (Loydi & Zalba 2009). Nutrients indung can favour weed establishment, with weeds establishing more vigorously in areas both trampled andsubject to deposition of dung. In a study of the potential for horse dung to act as an invasion window inmontane pampas grasslands, Loydi and Zalba (2009) found that the cover of introduced species was higher indung piles than in control plots. Dyring (1990) speculated that the redistribution of nutrients through uneven17

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013dung deposits and selective grazing would lead to exotic plants such as White Clover (Trifolium repens) andCats Ears (Hypochoeris radicata), which readily colonise dung and disturbed areas, becoming established indisturbed grassland and healthlands.Wild horse disturbance was found to enhance the spread of smothering weeds in New Zealand’s KaimanawaMountains (Rogers 1991; 1994). In the Australian Alps, exotic species were found to colonise the disturbedarea of wild horse tracks but did not tend to expand into untrampled areas (Dyring 1990). Dyring (1990)argued that the maintenance of tracks by wild horses enables the continued survival of exotic weeds.Horse occupied areas at Cowombat Flat were found to be characterised by a higher abundance of Yorkshirefog grass (Holcus lanatus, an invasive grass species native to Europe) and red fescue grass (Festuca rubra, anexotic grass species native to North America) than adjacent fenced horse exclosure areas (Wild & Poll 2012).In a weed assessment of the peatlands within the Eastern Alps Unit of the ANP for Parks Victoria (Thomas 2010unpublished report) Thomas (2010) made a series of assessments regarding wild horses and their relationshipwith weeds. These observations are unquantified so are only mentioned briefly here:• White clover (Trifolium repens) were found growing out of dung piles;• the spread of Birds foot trefoil (Lotus uliginosus) into peatlands from culverts on Davies Plain Trackappeared to be associated with wild horses;• there was evidence of wild horses grazing on Brown top bent grass (Agrostis capillaris), which may beaiding the spread of this weed; and• wild horses appear to avoid Yorkshire fog grass (Holcus Ianatus), providing this species with acompetitive advantage.3.3.5 Native tree mortalityWild horses have been found to affect native tree mortality in Australia. The chewing and stripping of bark byhorses can reduce regeneration of seedlings and may result in the death of mature trees. A significant negativerelationship was found between bark chewing damage and overall tree health in Guy Fawkes River NationalPark (Schott 2002). Impact assessments identified bark-chewing damage was most severe along drainage-linesand in close proximity with other water sources that are heavily used by wild horses. Schott (2002) found thatwild horses chew bark most intensely during summer and favour particular trees (Eucalyptus amplifolia and E.saligna and E. Moluccana).3.4 Impacts on peatlands (also known as mossbeds, peats, bogs, Sphagnum bogs, wet heathlands &mires)In Australia, peatlands are a rare ecological community, largely restricted to the highlands of Tasmania and thesouth-east corner of the mainland (Tolsma 2008b). “Alpine Sphagnum bogs and associated fens” are listed asan endangered ecological community under federal legislation (Environmental Protection and BiodiversityConservation Act 1999). Alpine bogs are also protected by Victorian legislation, where they are listed as athreatened community under the Flora and Fauna Guarantee Act (1988). These ecosystems are of nationalimportance due to their significance in providing critical habitat for several endemic flora and fauna species(many of which are threatened and several risk extinction) and the important role they play in the regulationof water release and flow downstream to major river systems, such as the Murray (DEWHA 2009a).Sphagnum moss is an important component of peatlands, integral to their structure and function. Wild horsesare known to have a detrimental impact on Sphagnum growth and integrity, with the resulting vegetation lossultimately leading to degradation of this ecological community (Dyring 1990; TSSC 2009). Wild horses aretherefore a major threat to Alpine Sphagnum peatland communities (Whinam & Chilcott 2002; Tolsma 2008b;TSSC 2009; DEWHA 2009a).18

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Bogs and peatlands are highly sensitive to damage by trampling and grazing. Preferential grazing of palatableherbs and grasses in Sphagnum bogs, combined with browsing of new growth of shrubs can lead to increaseddominance by unpalatable species (Whinam & Chilcott 2002). Sphagnum is easily crushed and broken up bywild horses trampling the delicate vegetation, selectively grazing and wallowing in pools and waterways (TSSC2009). Trampling may lead to the drying out of bogs, the loss of Sphagnum cover as well as changes to othervegetation, and creation of bare pavements (Theile & Prober 1999a; TSSC 2009). Once Sphagnum cover is lost,alpine soils and peat environments are very susceptible to desiccation, incision and soil erosion (TSSC 2009).In New Zealand wild horses have been found to severely degrade bog and wetland areas through tramplingand grazing, irrespective of local variations in horse density and habitat abundance (Rogers 1991). Thevulnerability of bogs in New Zealand was also found to increase with wetness (Rogers 1991). Whinam andChilcott (2002) found most Sphagnum peatland communities investigated in the ACT and New South Wales(NSW) were degraded by wild horses and other agents (i.e. fire, feral pigs, grazing and clearing). In 2008 thestatus of peatland systems in the Victorian Alps was investigated by Tolsma (2008a; 2008b). In the East AlpsUnit of the ANP, 97% (n=63) of peatland systems were found to be impacted (i.e. compacted, trampled orpugged) by wild horses (Tolsma 2008b). Only two peatlands assessed by Tolsma (2008b) in this unit of the ANPdid not show any signs of current wild horse activity: a fenced peatland at Davies Plain and an isolated systemon the south-east edge of the Unit. Whinam and Chilcott (2002) argue that wild horses are one of the greatestthreats to the survival of peatlands.Channelling is a form of erosion and water diversion which can result from wild horse activity. Trampling andwallowing cause channels to form in the disturbed Sphagnum. Channelling leads to changes in water flow, aswater exits the disturbed bog more rapidly. This action may completely alter the drainage pattern and result indrier conditions (Whinam & Chilcott 2002; TSSC 2009). The formation of channels is detrimental to the fensassociated with the bogs because the fens drain directly into the stream system and dry-up (TSSC 2009).Due to the access provided to peatlands following extensive bushfires throughout the Victorian Alps (primarilyin the 2003 fires) Tolsma (2008b) found that wild horse activity in burnt sub-alpine to alpine peatlands in theVictorian Alps varied from minor trampling at peatland margins to extensive pugging across almost the entireburnt peatland surface. On average, 25% of all peatland surface area assessed in the East Alps Unit of the ANPand 16% of peatland area assessed in State forest to the south was impacted by trampling (Tolsma 2008a) 1(see Photo 6). Trampling by wild horses restricts Sphagnum recovery in naturally-regenerating peatlands, andmay impact on some peatlands where restoration work is occurring (Tolsma 2008b). Tolsma (2008b) arguesthat in the Victorian Alps, many areas of burnt peatland, particularly in the East Alps Unit, are unlikely tocompletely recover while wild horses remain in the area (Tolsma 2008b).Peatland communities are likely to face further strain as climate change further alters their functioning(Dawson 2009b). At the same time it is suggested that the importance of the functional role that AlpineSphagnum peatlands play in water release and flow downstream will increase (DEWHA 2009a).1 'Area impacted' is the estimated proportion of the peatland system that was compacted, trampled or pugged by wildhorses.19

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Photo 6: Wild horse trampling of a bog area at The Playgrounds (source: Parks Victoria 2010)3.5 Impacts on waterways (streams and stream-banks)Wild horse activity can lead to the degradation of waterways and a reduction of water quality in streams,water holes and springs due to the trampling of stream banks and fouling of water holes (Csurhes et al. 2009).Wetlands, waterways and their adjacent riparian ecosystems generally have very high diversity andproductivity (Dawson 2009b), but are typically fragile and susceptible to damage by wild horses (and otherlarge hoofed animals) from selective grazing, trampling, pugging, wallowing and crossing (Costin 1954;Whinam & Comfort 1996; Williams et al. 1997; Evans 1998; Whinam & Chilcott 2002; McDougall 2007; NPWS2007; Prober & Thiele 2007; Dawson 2010). Streambanks are easily churned up and broken down by wildhorse hooves sinking into wet soils (Dyring 1990). Grazing by large hard-hooved herbivores can affectstreamside vegetation, stream channel morphology, shape and quality of the water column and the structureof the soil portion of the streambank, which has flow on effects for aquatic and terrestrial wildlife (Kauffmann& Krueger 1984; Rogers 1994; Beever & Brussard 2000).In the Victorian Alps, grazing and trampling within the vicinity of streams has been found to result in bankslumping and breakdown, vegetation disturbance and increased soil compaction (see Photos 7, 8 and 9). Thiscan lead to a decrease in infiltration, increased run-off as well as further drainage channel development,lateral erosion and stream incision (Dyring 1990).The Cowombat Flat and Native Cat Flat monitoring program has revealed significant changes to streamfunction and structure as a result of wild horse exclosure fencing. The unfenced stream areas had more bareground, were more entrenched and had distinct, open water channels, whereas areas within the exclosureshad indistinct channels, a more or less complete vegetation cover across the channel and no or little visibleopen water (Prober & Thiele 2007, Wild & Poll 2012). There was a significant increase in stream depth overtime in unfenced plots at Native Cat Flat while stream depth within the exclosures remained stable, suggestingaccelerated erosion in horse occupied areas (Wild & Poll 2012). Stream condition was better and consistentlyimproved over time in the horse exclosure plots which exhibited less pugging, stream slumping (collapse of thestream bank) and bare ground than unfenced areas (Wild & Poll 2012). The extra vegetation and lack of bareground have led to slower water flow along the stream in the horse exclosures (Prober & Thiele 2007, Wild &Poll 2012). In contrast the increased bare ground and lack of vegetation in unfenced areas is contributing tofaster flows and accelerated erosion of the stream channel, particularly at native Cat Flat where steep bankswith undercutting were observed (Wild & Poll 2012). Subsequently Prober and Thiele (2007) and Wild and Poll(2012) argue that at a catchment level, wild horse trampling and grazing may be impacting significantly onstream and catchment hydrology and water quality.20

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013In 2011 the AALC commenced a project that aims to quantify the impacts of wild horses on upland streamsand wetlands in the Australian Alps. The results of this study will be available in autumn 2013 and will providefurther evidence of the impacts of wild horses on sensitive stream and wetland environments.Photo 7: Wild horse pugging of waterway resulting in bank slumping, Murray Headwaters (source: Parks Victoria 2006).Photo 8: Wild horse damage to Murray River water source (source: Parks Victoria 2006)Photo 9: Wild horse trampling at the head of Moscow Creek, Cobberas Range, ANP (source: Parks Victoria 2006).21

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 20133.6 Impacts on faunaWild horse populations can alter the composition of bird, fish, crustacean, small mammal, reptile and antcommunities (Nimmo & Miller 2007) and have been identified as a major threat to a range of native wildlifespecies in the Victorian Alps. The 2001 AALC Natural Heritage Working Group Workshop of field staff andscientists, ranked wild horses as one of the top five priority fauna threats to the Australian Alps (Coyne 2001).Wild horses can affect native fauna through causing habitat modification or loss, and also through competitionfor resources (i.e. food, water, shelter and space) (Olsen & Low 2006; Nimmo & Miller 2007).3.6.1 Competition and altered food availabilityWild horses compete for resources with native herbivores, especially macropods, including: grey kangaroos(Macropus giganteus), red-necked wallabies (M.rufogriseus) and swamp wallabies (Wallabia bicolour). Variousstudies have demonstrated that high densities of wild horses correspond with reduced densities of macropods.Berman and Jarman (1988) found few signs of macropods in the Northern Territory in areas heavily grazed bywild horses. A study of wild horse impacts in Guy Fawkes River National Park by Lenehan (2010) providesevidence of wild horses displacing kangaroos from prime feeding habitats. Dung transects conducted in thenational park showed a strong negative relationship between wild horse dung and macropod dung. As wildhorses were removed from the transect area (as part of NSW National Parks and Wildlife Service (NPWS) horsecapture program, where 250 wild horses were removed) there was a significant progressive decline in horsedung and increase in macropod dung. Indicating that macropods were responding positively to decreases inhorse abundance (Lenehan 2010).Although it has not been investigated to date, it is possible that wild horses also compete with other nativemammals such as wombats (Vombatus ursinus). Wombats also feed primarily on grasses (such as Poa andother grass species and some shrubs) and like wild horses, dig below the snow to reach low vegetation duringwinter (Matthews 2010).Wild horse activity may constrain resources for many species and may increase the vulnerability of threatenedspecies (Nano et al. 2003). A reduction in the density of wild horses in Finke Gorge National Park andsurrounding area correlated with a striking increase in black-footed rock wallabies (Petrogale lateralis) andsmall fauna populations (Matthews et al. 2001). In 1990 no fresh black-footed rock wallaby dung wasrecorded, however after approximately 6000 wild horses were removed (and the population kept at lownumbers), the amount of fresh dung recorded steadily increased over the following ten years. It is suggestedthat the wild horse population may also have suppressed the endangered stick-nest rat (Zyzomyspedunculatus) in the West MacDonald ranges (Nano et al. 2003). Despite numerous surveys the species wasnot recorded between 1960 and 1996 and it was concluded the species was extinct. However in 1996 it wasrediscovered at numerous sites, a finding that corresponded with the removal of 30 000 wild horses (Nano etal. 2003). The major food plants identified in the diet of the stick-nest rat were also palatable to wild horsesand other introduced ungulates (ibid.).3.6.2 Habitat modificationWild horse grazing can result in a more open shrubland and increased area of bare ground, which in turncauses changes for associated wildlife (Zalba & Cozzani 2009). The removal of vegetation through grazing,trampling, wallowing and rubbing can result in a loss of shrub and ground vegetation connectivity. The habitatvalue of a site for animal species that require shrubs for shade, food or protection from predators and otherthreats may be reduced by the loss of this connectivity (Beever et al. 2008).Simplification of habitat by wild horses can lead to a reduction in foraging, nesting and roosting opportunitiesfor native animals, such as ground dwelling, foraging and roosting birds (O’Connor 2005). Zalba and Cozzani(2009) investigated the impact of wild horses on different bird communities in the Pampas grasslands in22

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Argentina. The presence of wild horses was associated with an increase in the rate of egg predation, whichvaried from 12.5% within exclosures to 70% in grazed areas. This was directly related to increased visibility ofthe nests and subsequent exposure to predators, nest trampling and reduced nesting sites. In Victoria’sBarmah Forest wild horses are listed as a threat to some ground nesting birds including the AustralasianBittern and Little Bittern (SAC 1997a; 1997b). Due to a lack of research it is unknown if wild horses pose athreat to any birds in the Victorian Alps.Wild horses may potentially cause the collapse of wildlife burrows (Theile & Prober 1999a). In the VictorianAlps many medium and small mammals, such as the bush rat (Rattus fuscipes), swamp rat (R. lutreolus) andbroad-tooothed rat (Mastacomys fuscus), use burrows that may be susceptible to trampling damage. Wombatburrows that, for example are dug in open ground with little protective cover over the burrow may besusceptible to damage by wild horses. In the USA, exclosure plots around springs exhibited more smallmammalburrow entrances than plots at horse-grazed springs (Beever & Brussard 2000).The affect that wild horses have on invertebrate eco-engineers such as ants in the Victorian Alps is currentlyunknown. Beever and Herrick (2006) found a greater abundance of ant mounds in sites where wild horses hadbeen removed over ten years ago. This may have a substantial influence on ecosystem health and the survivalof other species.Extensive damage to the structural complexity of ground-level vegetation and habitat caused by wild horsesthreatens the reptile and amphibian species of the Victorian Alps. Structural complexity of habitat is a criticalrequirement for many reptile species and communities (Clemann et al. 2001). Litter cover, ground cover andthe degree of soil compaction are all important elements for reptiles (e.g. Brown 2001; Jellinek et al. 2004).Similarly, most amphibian species in the Australian Alps rely on the structural complexity formed by vegetationalong the margins of streams and ponds, especially for male calling and female egg laying sites (Osborne 1990;Green & Osborne 1994). Grazing and trampling by ungulates such as wild horses in the alpine region affectshabitat complexity through: direct removal of vegetation; destruction of structural components in the groundlayer; and, soil compaction (Clemann et al. 2001). For example, the alpine water skink (Eulamprus kosciuskoi)(photo 10), alpine she-oak skink (Cyclodomorphus praealtus) and alpine bog skink (Pseudemoia cryodroma) arethreatened by wild horse impacts on peatlands, wet heath and riparian areas, which provide vital habitat forthese species (Clemann et al. 2001; Clemann 2001; Meredith et al. 2003; Steane et al. 2005).As discussed, peatland habitats are extremely vulnerable to wild horse activity. Horse damage to peatlands hasimmediate effects on habitat structure, and leads to hydrological consequences such as deteriorating waterquality and loss of landscape structure. Damage to habitat caused by wild horses is specifically identified as athreat to the federally endangered alpine she-oak skink, which occurs in close proximity to bogs, streams andwet heaths. Recommended actions to mitigate this threat include the development and implementation of amanagement plan for the control of wild horses (DEWHA 2009b).Historically, the threatened alpine tree frog (Litoria verreauxii alpine) was widespread and abundant acrossmost of the high country of mainland south-eastern Australia (Clemann & Gillespie 2004). The species hassince retracted from much of its previous habitat. Populations of the alpine tree frog are known to be subjectto a number of threatening processes, including the trampling of habitat by wild horses (Clemann & Gillespie2004). The threat of further population declines is likely and remains a cause for concern (Brown et al. 2007).Small mammal communities may be affected by grazing ungulates such as wild horses indirectly throughalteration in vegetation structure, water quality and other site characteristics (Giuliano & Homyack 2004).Removal of ungulates (mostly cattle) grazing from streams and associated riparian zones led to an increase inmammalian species richness and abundance within two years in a study in south west Pennsylvania (USA)(Giuliano & Homyack 2004). A similar result was shown in the central Kimberley across several habitats after23

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013the removal of cattle (Legge et al. 2007). In a study of horse impacts using exclosures in the USA, qualitativedifferences were observed in small mammal activity (Beever & Brussard 2000).There are a limited number of small mammal species in the Australian Alps, and complexity of vegetationstructure is associated with habitat quality for these species (Carron 1985). The habitat of small mammals inAlpine regions is extremely sensitive and threatened by climate change (Green et al. 2008). A species ofparticular concern is the broad-toothed rat Mastacomys fuscus (Green & Osborne 2003 and references within)whose habitat is shrinking and is likely to face a further declines with climate change (Green et al. 2008). Thebroad-toothed rat inhabits areas of moderate-to-dense grass and/or sedge cover (Green et al. 2008). Thisenvironment is favoured by wild horses for grazing and the habitat can be broken-up through wild horseactivity. O’Brien et al. (2008) found populations of broad-toothed rats that existed in isolated patches werelikely to suffer local extinction due to low levels of success emigrating through unsuitable habitat to reachsuitable habitat.3.6.3 Threatened fauna in the Victorian AlpsHerpetofauna (reptiles and frogs) are central components of the vertebrate fauna of the Victorian Alps andseveral threatened species are endemic to alpine areas (Clemann et al. 2001). A large proportion of this groupare officially listed as threatened at the federal and state level (Appendix 3). Herpetofauna in this region aregenerally dependent on bog, grass and wet heath habitats (Clemann et al. 2001). As previously mentioned,most alpine herpetofauna are intimately linked with habitat structure, particularly close to ground level(Clemann et al. 2001). Wild horses are believed to be one of the processes directly or indirectly threateningthese species (Clemann et al. 2001). For example, the alpine water skink (Eulamprus kosciuskoi) (photo 10) islisted as critically endangered in Victoria and is only found in the high altitude areas of south-eastern Australia(Steane et al. 2005). Steane et al. (2005) found the preferred habitat of alpine water skinks to be mossbeds ingood condition (i.e. high cover of live Sphagnum and low cover of bare-ground, rock and non-mossbedvegetation). Any threat to Sphagnum cover, such as that posed by wild horse grazing and trampling, severelythreatens the habitat of the alpine water skink (Steane et al. 2005). Horses have impacted much habitat thatwas previously occupied by the alpine water skink on Forlorn Hope Plain in the Buchan headwaters.Consequently, to protect threatened alpine water skink populations from trampling by wild horses, wild horseexclusion fences at Davies Plain around two sub-alpine bogs have been constructed (see section 3.3.3).Photo 10: The alpine water skink (Eulamprus kosciuskoi), an endangered species whose habitat is threatenedby wild horses (Source: Nick Clemann).24

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 20134. Wild horse biosecurity issuesWild horses are a prominent reservoir for exotic and endemic diseases and parasites that can affect nativewildlife, domestic horses, stock and humans (Bradshaw et al. 2007). The spread of pests and disease by feralanimals is considered by the federal government of Australia to be a major biosecurity risk (DAFF 2010).Wild horses in the Victorian Alps have the potential to be a biosecurity risk through harbouring andtransmitting disease. Diseases of concern are either those that have the potential to establish or exist alreadywithin Australia. Diseases are highly variable, for example they may be equine specific or they may affectseveral species, transmissibility varies, and symptoms range from minor ailments to mortality. The wild horsepopulation in the Australian Alps poses a potential risk to other species that may co-habit with them such asnative species, pigs, deer and cattle.Wild horses have the potential to transport the Amphibian Chytrid fungus (Batrachochytrium dendrobatidis)between waterbodies and between catchments. This pathogenic and highly transmissible fungus, results in thedisease chytridiomycosis, that has caused the decline or extinction of up to 200 species of frogs (Skerratt et al.2007). Skerratt et al. (2007, p.125) refer to the impact of this fungus as the, “most spectacular loss ofvertebrate biodiversity due to disease in recorded history”. As well as being a potential vector of this disease,horses may introduce novel strains of the fungus to new areas. Some fungus free frog populations remain inplaces such as Grey Mare in Kosciusko National Park and keeping them fungus free is a critical biodiversitypriority.Wild horses can play a potential role in a disease outbreak of a newly imported disease (Biosecurity Australia2009). There are many steps involved in the outbreak of a new disease. Wild horses must first be exposed tothe disease, once exposure occurs, a range of outbreak scenarios are possible from no spread to widespreadestablishment. Outbreak scenarios are dependent on the epidemiology of each disease agent. The role thatwild horses play in a potential disease outbreak scenario for a newly imported disease was considered in a riskassessment by Biosecurity Australia (2009). In general, wild horses were thought to have a limited ability toaffect domestic horse populations because of their remoteness. Equine Influenza received the highest riskassessment (moderate). There was an outbreak of Equine Influenza in 2007, which led to prohibitions on horsemovements in Victoria to control the spread of the disease, however, it was eliminated (Animal HealthAustralia 2009).There is little known about the incidence and prevalence of many existing diseases of domestic horses inAustralia, and much less is known about the frequency of disease in wild horses. There are a range of zoonoticdiseases (diseases that horses can share with humans and other livestock) which are present in Australia andmay be of concern including anthrax, Hendra virus disease, Murray Valley Encephalitis, leptospirosis,Australian bat lyssavirus, Salmonellosis, Tetanus and ringworm. It is not known how these diseases may affectnative species.Hendra virus is a relatively new and emerging disease, first reported in 1994 in Queensland (Equine SpeciesWorking Group n.d). Subsequently there is not a great deal known about the disease, however, horses arelikely to be dead-end hosts. It causes severe respiratory illness in horses and is frequently fatal. Humans cancontract the disease if they have direct contact with blood or saliva of an infected horse (Equine SpeciesWorking Group n.d).Murray Valley Encephalitis is a virus spread by mosquitoes that can infect many animals, including horses andhumans (DPI 2012). The virus causes swelling of the brain and is potentially fatal for humans (DPI 2012).Outbreaks in south eastern Australia are generally associated with wet conditions. In 2011 a widespreadoutbreak infected domestic horses in north and north western Victoria (DPI 2012).25

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Humans, domestic animals and wildlife are susceptible to the bacterial disease Leptospirosis and infectedanimals may become sick or show no symptoms at all (Equine Species Working Group n.d). Salmonellosis is abacterial disease that can infect horses and humans and is of concern because some strains exhibit resistanceto multiple antibiotics (Equine Species Working Group n.d). Salmonella may impact upon many species(including native wildlife) particularly if they are under stress. Australian bat lyssavirus is the only type of rabiesin Australia; however, there have been no reports of horses being affected by this disease. Tetanus can be afatal disease and its spores are widely distributed, usually in soil, dust and manure; horses and humans are themost susceptible of all of the animal species to tetanus (Equine Species Working Group n.d). Ringworm is afungal skin disease. Numerous species can transmit ringworm to humans (Equine Species Working Group n.d).5. Gaps in knowledgeThere has been a limited amount of research into wild horse biology, behaviour and ecological impacts in theAlpine region to-date. An important area for investigation that will aid in guiding effective management is therelationship between wild horse density and damage (Dawson et al. 2006). Quantification of the relationshipbetween density, impact and population control has been identified as a priority research area for themanagement of wild horses by the AALC. The AALC has initiated a project that aims to address this gap bydeveloping a protocol for determining horse density at the local scale and investigating the influence of horsedensity on impacts. Site-specific research using experimental trials to determine local levels of resistance toimpact would also provide important information (Venn et al. 2009).Previous aerial surveys of wild horse populations have not covered the whole area occupied by horses and arelikely to significantly under-estimate the total population size. There are large areas known to be occupied bywild horses that have been excluded from previous aerial surveys, including Byadbo and adjoining areas of theAlpine National Park and adjacent State Forests (Dawson 2009). There are plans to cover a larger portion ofthe area occupied by wild horse in future aerial population surveys in order to obtain a more accurate estimateof the total Victorian Alps wild horse population size. Wild horses do not currently occupy all suitable habitatwithin the Victorian Alps. Mapping potential horse habitat that could potentially be colonised by wild horses isrequired and work has commenced to address this gap (Dawson 2009).The effects of wild horse grazing on vegetation have been investigated at small spatial scales; however havenot been investigated at a broad spatial scale. The effects of chronic disturbance over broader areas issubsequently not well understood within the Victorian Alps, greater Alpine area, Australia or internationally(see Beever et al. 2003; Beever et al. 2008). To-date only studies at a small single spatial scale have beenconsidered. These studies are important; however they may not be representative of the Victorian Alps systemmore broadly and may not represent the conditions prevalent on a landscape scale (Nimmo & Miller 2007)Finally there is a need to further investigate how the environmental impact of wild horse’s changes throughtime as the environment varies (e.g. drought, fire, climate change etc). The environmental impact of wildhorses may be exacerbated in drought years, as they tend to concentrate around watering points (Dawson2010). Impacts are also likely to increase substantially after fire (such as those that occurred in Victoria in 2003and 2006/07) when Alpine environments such as peatlands are particularly susceptible. Climate change islikely to influence the magnitude of the impacts of wild horses in future years. Alpine species and communitiesare amongst the most vulnerable to the effects of climate change and therefore their resilience to climatechange requires that they be protected and maintained in as healthy a condition as possible (DSE 2010). Thispressure combined with the impact of wild horses requires further investigation.26

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Appendix 1: Officially listed plant ecological communities at risk ofsevere damage from wild horse activityFloristic Community orEcological Vegetation Class EPBC FFG Main consequencesAlpine Bog Community Endangered* Listed Disruption of plant regeneration, selective grazingleading to compositional changes, weed invasion,severe trampling, soil loss, and loss of hydrologicalfunction.Fen (Bog Pool) Community Endangered* Listed Disruption of plant regeneration, selective grazingleading to compositional changes, weed invasion,severe trampling, and loss of hydrological function.Alpine SnowpatchCommunityCaltha introloba HerblandCommunityMontane Swamp ComplexCommunityListedListedListed* Alpine Bog and Fen Pool communities are combined in the EPBC listingSevere trampling, soil loss, displacement ofvegetation, weed invasion, selective grazingleading to compositional changes.Soil loss, displacement of vegetation, weedinvasionSevere trampling, soil loss, displacement ofvegetation, weed invasion, smothering by dungpiles, selective grazing leading to compositionalchanges.36

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Mountain Aciphyll (Aciphyllasimplicifolia)r Selectively grazed in grasslands & bog margins. Highly palatable,most common in ungrazed areas.Native Wintercress (Barbareagrayi)v Trampling & loss of habitat - bogs & stream margins. Highlypalatable to stock.Grassy Moonwortv Trampling of grassy habitat. Intolerant of disturbance.(Botrychium lunaria)Baw Baw Daisy (Brachyscomer Trampling & loss of habitat - alpine wet heathlands & bogsobovata)Marsh Daisy (Brachyscomer Trampling & loss of habitat - alpine wet heathlands & bogs.radicans)Spreading Bitter-cress(Cardamine astoniae)v Trampling of habitat - wet grasslands and bog margins. Palatableto stock.Star Sedge (Carex echinata) v Trampling & loss of habitat - alpine wet heathlands & bogs.Palatable to stock.Raleigh Sedge (Carex raleighii) r Trampling & loss of habitat - alpine wet heathlands & bogs.Palatable to stock.Marsh Tree-moss (Climaciumv Physical damage to habitat - within streamsdendroides)Creeping Coprosmar Trampling & loss of habitat - alpine wet heathlands & bogs.(Coprosma perpusilla)White Billy-buttons(Craspedia alba)v Trampling & damage to habitat - Caltha herbfields & valleybottoms. Palatable to stock.Tufted Hair-grass(Deschampsia caespitosa)r Trampling & loss of habitat - Caltha introloba Herbland Community& fensSkirted Bent-grass (Deyeuxiav Trampling & loss of habitat - alpine wet heathlands & bogs.talariata)Tailed Eyebright (Euphrasiar Trampling & loss of habitat - Alpine Sphagnum bogscaudata)Slender Gingidia (Gingidiaharveyana)v Trampling & loss of habitat - stream margins. Highly palatable,hence selectively grazed.Alpine Holy-grass (Hierochloev Trampling & loss of habitat - alpine wet heathlands & bogs.submutica)Tussock Woodrush (Luzular Trampling & loss of habitat - grassy edges of wetlandsalpestris)Slender Woodrush (Luzulav Trampling & loss of habitat - damp grasslandsatrata)Spreading Clubmossr Trampling & loss of habitat - alpine wet heathlands & bogs.(Lycopodium scariosum)Hump Moss (Meesia muelleri) r Trampling & loss of habitat - boggy grasslandsBranched Caraway(Oreomyrrhis brevipes)v Selective grazing in rocky habitat. Palatable, and now extremelyrare in grazed areas.Wedge Oschatzia (Oschatziar Trampling & loss of habitat - alpine wet heathlands and bogs.cuneifolia)Matted Rice-flower (Pimeleabiflora)r Possible selective grazing in open heath & grassland. Rare ingrazed areas.Hard-head Bush-pear Trampling & loss of habitat - margins of alpine wet heathlands(Pultenaea capitellata)Southern Sheep-grass(Rytidosperma australe)e Trampling & loss of habitat - Caltha introloba Herbland Community38

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013Appendix 3: Officially listed or threatened fauna species potentially atrisk from feral horse activity in the eastern Victorian AlpsSpecies EPBC FFG DSE 2 Main consequencesAlpine Water Skink(Eulamprus kosciuskoi)Listed CriticallyEndangeredLoss and degradation of habitat - alpine bogand alpine fen (bog pool) communitiesAlpine Bog Skink(Pseudomoia cryodroma)Listed Endangered Loss and degradation of habitat - alpine bogand alpine fen (bog pool) communities,woodlands and heathlandsAlpine She-oak Skink(Cyclodomorphuspraealtus)Guthega Skink (Liopholisguthega)Mountain Skink (LiopholisMontana)Alpine Tree Frog (Litoriaverreauxii alpina)Endangered Listed Endangered Loss and degradation of habitat - alpinetussock grasslands, alpine low heathlandsUnderconsiderationListedCriticallyEndangeredData DeficientVulnerable Listed CriticallyEndangeredLoss and degradation of habitat - alpineheathlandsLoss and degradation of habitat - alpinewoodlandsLoss and degradation of habitat - alpine andsubalpine wetlands, riparian zones andephemeral pools.39