The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

Background Paper 1 of 3

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps

Wild horse exclusion plot, Native Cat Flat 2004 (source: Parks Victoria).

Parks Victoria May 2013

This paper was written by: Joanna Axford 1, Michelle Dawson 2 and Daniel Brown 3 1 Formerly Parks Victoria, Bright 2 Eco Logical Australia 3 Parks Victoria, Bright

Acknowledgements : 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 Parks Victoria) reviewed this paper. Joanne Lenehan, PhD candidate (University of New England), provided unpublished results of her study into wild horse impacts in Guy Fawkes River National Park.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 of Melbourne) and H. Crabb (Principal Veterinary Officer-Intensive Farming Systems, DEPI Victoria) were consulted on various sections of this paper.

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

Acronym List ABA: Australian Brumby Alliance

ABMA: Alpine Brumby Management Association

AALC: Australian Alps Liaison Committee

AANPs: Australian Alps National Parks

ANP: Alpine National Park

BAW: Bureau of Animal Welfare

COP: Code of Practice

DEPI: Department of Environment and Primary Industries

EPBC: Environment Protection and Biodiversity Conservation Act 1999

FFG: Flora and Fauna Guarantee Act 1988

KNP: Kosciuszko National Park

RSPCA: Royal Society for the Prevention of Cruelty to Animals

SOP: Standard Operating Procedure

VBA: Victorian Brumby Association

The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

Table of Contents

Introduction to Wild Horse Background Papers ...... 1 1. Introduction ...... 2 2. Wild horse ecology in the Victorian Alps ...... 2 3.1 Wild horse distribution ...... 2 3.2 Wild horse population trends ...... 3 3.3 Wild horse demography ...... 6 3.4 Wild horse social organisation and movement ...... 6 3.5 Wild horse habitat and diet preferences ...... 7 3.6 Wild horse mortality factors ...... 8 3. Wild horse environmental impacts ...... 9 3.1 Environmental impacts of wild horses ...... 9 3.2 Impacts on soil and substrate ...... 11 3.3 Impacts on vegetation ...... 14 3.4 Impacts on peatlands ...... 18 3.5 Impacts on waterways (streams and stream-banks) ...... 20 3.6 Impacts on fauna ...... 22 4. Wild horse biosecurity issues ...... 25 5. Gaps in knowledge ...... 26 References ...... 27 Appendix 1: Officially listed plant ecological communities at risk of severe damage from wild horse activity ...... 36 Appendix 2: FFG-listed and EPBC-listed plant species potentially at risk from wild horse activity in the eastern Victorian Alps ...... 37 Appendix 3: Officially listed or threatened fauna species potentially at risk from feral horse activity in the eastern Victorian Alps ...... 39 The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

Introduction to Wild Horse Background Papers Horses (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, self sustaining, wild populations is by definition a feral animal. However, some people are uncomfortable with the term ‘feral’ being associated with horses and prefer the terms ‘wild horse’ or ‘brumby’. ‘Brumby’ is a colloquial term often used in Australian folklore; however some people believe the term elicits a romanticised view of horses and detracts from their environmental impacts. In this series of papers the term ‘wild horse’ will be used, 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 population of wild horses in the world, with more than 300 000 (Dobbie et al. 1993). Wild horses are a pest species in Australia, that is, an “animal that has, or has the potential to have, an adverse economic, environmental or social/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 natural values of the region (Coyne 2001). The “degradation and loss of habitat caused by feral horses” is listed as a potentially 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 management and 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 first section of this paper considers the ecological dimensions of wild horses in the Victorian Alps including their distribution, population trends, demography, habitat, diet and mortality factors. The environmental impacts of wild 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 paper provides the social context for wild horse management in the Victorian Alps. A brief history of wild horses in the region and the major stakeholder groups involved is outlined. The socio-economic and cultural heritage values of wild horses are then explored followed by a discussion on public perceptions about wild horses and their management in the Victorian Alps. Research from national and international investigations into perceptions 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 of wild horses in the Victorian Alps and considers control methods for managing wild horses. An overview of how wild horses have been managed in the Victorian Alps and the legislation and policy framework for wild horse management 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 with experts where possible. The papers provide a foundation for discussion concerning the future management of wild horses within the Victorian Alps.

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

1. Introduction In Victoria wild horses (Equus caballus ) occur in the Victorian Alps with a smaller population present in the Barmah Forest, on the Murray River (Menkhorst 1995; Wright et al. 2006). Wild horses are considered a significant environmental threat to the Victorian Alps (including the Alpine National Park (ANP) and adjacent State forests). The “degradation and loss of habitat caused by feral horses” is listed as a potentially threatening process under Victoria’s Flora and Fauna Guarantee Act (1988). This paper will explore the ecological dimensions of wild horses in the Victorian Alps and the extent to which they are affecting the natural values of the region.

Several studies and reviews have been conducted on the ecology and environmental impacts of wild horses in various 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 the Victorian Alps, information in this paper is also drawn from national and international literature as well as anecdotal information on wild horses in the Victorian Alps.

2. Wild horse ecology in the Victorian Alps 3.1 Wild horse distribution

Wild horses in the Australian Alps are relatively isolated from populations elsewhere in Australia. The largest populations in Australia occur in dry and tropical environments, mainly in the Northern Territory and Queensland, but also Western Australia and South Australia (Dobbie et al. 1993). In much of Australia, drought limits the distribution of wild horses (Dobbie et al. 1993). However, this is not evident in the Australian Alps which occupy wetter bioregions with more consistent rainfall (Hobbs & McIntyre 2005). The distribution of wild horses in Australia has also been strongly influenced by human intervention including farming infrastructure such as fencing (McKnight 1976).

Wild horses were initially introduced into the Australian Alps by European settlers in the 1830s. Graziers managed the distribution (and numbers) of wild horses to varying degrees from the mid-1800s up until cattle grazing ceased early this century (Walter 2002; Foster 2004). Non-human influences on wild horse distribution in the Alps include preferred habitat, geographical barriers and natural events such as severe snow storms, fire and drought (Walter 2002). Between 1990 (Dyring 1990) and 2002 (Walter 2002) wild horse distribution appeared to be relatively stable in the ANP, however, in the past ten years wild horse populations have expanded 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 Alps that is currently not occupied. Furthermore, it is predicted that with climate change, areas at higher elevation will 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 is connected to a population in Kosciuszko National Park, NSW to the north (Figures 1 and 2). It extends south to the Nunniong Plains, as far west as Mt Pinnibar and Buenba Creek, and to Deddick and Amboyne east of the Snowy River. The second, smaller population is on the southern Bogong High Plains, between Falls Creek and Mount Hotham, and in the headwaters of the Cobungra, Bundara and Victoria Rivers (Ethos NRM 2012). The Bogong High Plains/Cobungra population is isolated from the Eastern Alps population by around 30km and considered to have a lower density of horses than the east Alps population (Ethos NRM 2012) (figure 2). Both populations, while situated predominantly within the ANP, extend into adjacent State forests and reserves and, probably, private land.

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

Records of small groups of horses have occurred at other disjunct locations across the Victorian Alps from time to 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 Mt Wellington in the Alpine National Park and the adjacent Carey State Forest. This group of horses is suspected to have been illegally introduced, but was gradually trapped and removed by Parks Victoria and DEPI over the subsequent summer and autumn. In early winter 2010, another new group was discovered in State forest at Connors Plain, north-west of Licola. This group was also trapped and removed. Monitoring continues in both areas to ensure that all the horses have been captured.

Mount Buffalo National Park

Alpine National Park

Alpine National Park

Snowy River National Park Alpine National Park

Figure 1: Estimated wild horse distribution in the Victorian Alps, showing the two disjunct populations. This distribution map is based on a report by Ethos NRM (2012) that used previous horse records and interviews with a broad range of stakeholders (with knowledge and experience of wild horses in the Victorian Alps) to estimate the distribution of wild horses in the Victorian Alps. NB: This map is based on anecdotal qualitative information and provides only a broad guide to wild horse distribution.

3.2 Wild horse population trends

The most reliable estimates of wild horse population size have come from aerial surveys across the Australian Alps National Parks (AANPs) conducted in 2001, 2003 and 2009 (Walter & Hone 2003; Dawson 2009). These surveys were developed with the aim of providing a repeatable and robust method for monitoring wild horse population 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-west transects at two kilometre intervals and analysed using line-transect techniques (Walter & Hone 2003). This method was designed to minimise several potential sources of bias such as decreasing detectability of horses with distance from the aircraft (Walter & Hone 2003), and counting horses more than once (see Linklater & Cameron 2002).

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

Figure 2: Estimated distribution and relative density of wild horses in the Victorian Alps. This map is based on a report by Ethos NRM (2012) that used previous horse records and interviews with a broad range of stakeholders (with knowledge and experience of wild horses in the Victorian Alps) to estimate the distribution and density of wild horses in the Victorian Alps. NB: This map is based on anecdotal qualitative information and provides only a broad guide to wild horse distribution and density.

Wild horse populations can increase at a maximum rate of 21-37% per annum, depending on local environmental conditions (Eberhardt 1987; Garrott et al. 1991a; Linklater et al. 2004; Grange et al. 2009; Scorolli 2010). Populations do not sustain these levels of growth indefinitely. Population growth slows, stops or becomes negative when horses are removed from the population by people (e.g. Garrott & Taylor 1990); or when populations become limited by resources such as food or water (Dobbie et al. 1993; Grange et al. 2009; Scorolli & Lopez 2010). The wild horse populations in the Australian Alps were estimated to be increasing at 21% per annum between 2003 and 2009 after broad-scale, intense bushfires in the summer of 2002/3 reduced populations by approximately 54 percent (Dawson 2009). In a study of three small wild horse populations in the Australian Alps (one in Victoria and two in New South Wales) prior to the 2002/3 bushfires, Dawson and Hone (2012) observed that the populations were either stable or increasing at a rate of up to nine percent per annum. More stable rates were observed in long established unmanaged populations (including Cowombat Flat) and a higher rate of increase in an area where human intervention had recently been reduced (Dawson and Hone 2012).

Trends in the size of the wild horse population in parts of the ANP have been derived using aerial survey results since 2001 (Figure 3). The population appears to have fluctuated between 2001 and 2009, primarily as a result of the severe and extensive bushfires in 2002/3 (Dawson 2009). The estimates show a rapid growth phase between 2003 and 2009 (with an annual growth rate of 21%) consistent with recovery post-fire. This rapid population increase has occurred despite the removal of more than 700 horses by Parks Victoria during this period. The size of the population in the surveyed portion of the ANP has been in the order of 1000 to 3500 horses between 1990 and 2009, with the highest estimates in the most recent 2009 survey (3442 horses ± 874 SE). However, these estimates are based on aerial surveys that cover less than half the area known to be occupied by wild horses (ELA 2012) and there is no indication that the population has stopped growing since

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

2009. Thus, the true size of the wild horse population in the Victorian Alps is expected to be significantly higher.

Population modelling has been undertaken to estimate the wild horse population size for the entire Victorian Alps. This modelling involves using estimated wild horse density and distribution mapping to extrapolate the population estimates derived from aerial surveys across the entire area occupied by wild horses. Wild horse population growth is estimated using a logistic growth model that calculates population growth towards an estimated carrying capacity (derived from field studies), which varies in response to environmental variability (rainfall) (ELA 2012). This modelling suggests that the entire Victorian Alps wild horse population is now approximately 9718 horses (SE: 8151 – 10 896) (ELA 2012) (figure 3). This represents an average wild horse density of 3.4 per km 2 across their current distribution in the east Victorian Alps. The highest documented densities of wild horses in the Australian Alps is 6.4 km -2 at Cowombat Flat, Victoria, at a time when the population was stable (Dawson & Hone 2012).

12000 Estimated population size (aerial survey area only) Estimated population size (extrapolated for whole Victorian Alps) 10000 Horses removed

8000

6000 Number of Horses of Number 4000 Bushfires

2000

88 95 121 185 193 150 122 145

21594902 1011 2293 3442 7087 9718 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Year

Figure 3: Estimates of wild horse population size ± SE derived from aerial surveys of the surveyed portion of the ANP (Dawson 2009) (blue columns) and extrapolated for the whole area occupied by wild horses in the Victorian Alps (ELA 2012) (green columns). The 2012 estimate is derived from modeling wild horse population growth from 2009 towards estimated carrying capacity (ELA 2012). The number of horses removed from the Victorian Alps through Parks Victoria management programs since 2005 is also included (red columns).

The Bogong High Plains wild horse population remained relatively static at around 80 - 100 horses between 2005 and 2009 (Dawson and Miller 2008), despite the removal of 102 horses over the same period. However, aerial surveys indicate that the population has decreased in the equivalent survey area between 2009 and 2012, from around 90 to 50 horses (figure 4). Seventy six horses were removed during this same period.

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

140 Estimated Horse Population Horses Removed 120

100

80

60 55

37 38 40 31 Number of Horses of Number

20 10 11 6 7 92 95 88 51 0 2005 2006 2007 2008 2009 2010 2011 2012 Year

Figure 4: Estimates of wild horse population size ± SE for the Bogong High Plains population only. The number of horses removed from these areas by Parks Victoria since 2005 is also included (red columns). Population estimates are derived from aerial surveys (Dawson and Miller 2008).

3.3 Wild horse demography

Wild horses have an annual breeding season, producing one young at a time (Grange et al. 2009). The first young are usually produced when females are three years of age. When wild horse density is low and food is abundant they occasionally reproduce at two years of age (Berger 1986; Duncan 1992). During a three year study 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 foaling rates until the onset of senescence at 15-18 years of age (Garrott & Taylor 1990; Garrott et al. 1991b; Duncan 1992; Linklater et al. 2004; Grange et al. 2009). Foals are usually born in the summer months when food availability is at its highest (after an 11 month gestation) but can be born at any time of year (Dawson unpublished data). Foaling rates observed for wild horses in three separate populations in the Australian Alps between 1999 and 2002 were lower than those reported in other environments with 42-62% of adult females observed with foals (Dawson & Hone 2012).

Between 1999 and 2002 survival rates of adult wild horses in the Australian Alps were generally high (91% per annum) with little annual variation, while survival rates in the first three years of life are lower and more variable (63-75% per annum) (Dawson & Hone 2012). This is similar to wild horse populations from around the world (Garrott & Taylor 1990; Linklater et al. 2004; Grange et al. 2009; Scorolli & Lopez Cazorla 2010). There is no 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 movement

Wild 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 been

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

forced out of their harems; they generally occur alone or in groups of two or three (Dobbie et al. 1993). The average group size (harem and bachelor groups) from three sites across the Australian Alps was 5.65 (± 0.51 SE) (Walter & Hone 2003), while Drying (1990) found that harem group sizes in the Alpine region ranged from two to 11 individuals, with groups typically consisting of one stallion, two mares and one foal. Wild horses rarely have periods of social isolation during their lifetime except for bachelors in their pre-harem formation stage (van Dierendonck 2006). Harem groups tend to be stable breeding units and generally favour permanent locations around reliable water sources (Dobbie et al. 1993). Within harem groups , adult mares form a long- term stable nucleus, while the breeding stallion is regularly replaced (van Dierendonck 2006) . Bachelor groups are 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). The home 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 is information available from other environments. Home range sizes vary within a region and between regions. In Queensland and central Australia wild horses were estimated to have a home range of approximately 100km² and 70km² respectively (Dobbie et al. 1993). In contrast, wild horses at Kiamanawa in New Zealand, which has a similar climate to the Australian Alps, had home ranges 0.96 to 17.7 km 2 (Linklater 2000). Given the climatic similarities, 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 from the 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 an extensive view of their surrounds (Dobbie et al. 1993). With well developed hearing any movement is readily detected (Dobbie et al. 1993).

3.5 Wild horse habitat and diet preferences

Wild horses occupy a range of habitats across Australia and the world. While they are best adapted to open grassy plains they will also use rugged country (Norris & Low 2005). Wild horses are present from the highest to the lowest elevations in the Australian Alps (Walter 2002). Some groups may migrate to lower elevations in winter 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 six kilometres from the Victorian border) made extensive use of heaths and grasslands for feeding, whilst avoiding the forests at all times of the year; this preference for open areas was broad-based with no discrimination between feeding and other activities. The preference for grasslands over forest is universal for wild horses (Pratt et al. 1986; Keiper & Berger 1982; Berger 1986; Linklater et al. 2000). The only exception has been observed in the middle of the day in summer when wild horses seek refuge from the heat and horseflies ( 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 a strong preference for the greatest concentrations of high quality food (green plant matter); when green plant matter becomes sparse, the horses’ tactic is to search out areas with the greatest concentrations of perennial herbaceous 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 forward- cut front incisors they are able to graze close to the ground (Dobbie et al. 1993). Horses have a different digestive system to most ungulates (hoofed mammals), which enables them to consume large quantities of low quality food and survive on a lower quality diet than cattle (Janis 2007). Cattle require time to chew their cud 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 & Low 2005). If food is plentiful horses will graze near water sources (Dobbie et al. 1993).

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

3.6 Wild horse mortality factors

With few predators, unmanaged wild horse populations may increase in size and distribution until they approach carrying-capacity; at this point the population size stabilises as a result of a decrease in birth rates and survival rates caused by limited food availability (Grange et al. 2009; Scorolli & Lopez Cazorla 2010). For example, in the Camargue in France, Grange et al. (2009) found that a decrease in available food resources, as a result of increasing density, caused a loss of body condition and the survival of foals and adult females decreased with increasing density.

In sub-alpine and montane environments of the Australian Alps, there is evidence that between 1999 and 2002, the growth of three wild horse populations was limited by food availability (Dawson & Hone 2012). The density 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 poorest condition, recruitment (from birth to 3-years-old) was low, pasture biomass was low and population growth was zero. In general however, unlike the Camargue example above, wild horses in the Australian Alps are not contained and do not currently occupy their entire potential range (Dawson 2009). Therefore there is scope for 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. In stochastic 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, in particular drought, snow and fire, which have lead to dramatic declines in wild horse populations (thus preventing 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 1982-83 was reported to have led to a dramatic decline of most wild horses in this area (Walter 2002), similar patterns are observed in central Australia (Dobbie et al. 1993). Drought can affect horses through thirst, starvation and ingestion 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 snow cover in the alpine area (Walter 2002). In winter wild horses at higher elevations, such as those on the Bogong High Plains, have to dig through snow to access food for many weeks of the year which leads to a loss of body condition in the horses (Dawson unpublished data). In some cases severe snow events have resulted in mortality and in one historic event in the Brindabella’s (Australian Capital Territory (ACT)) an entire population was wiped out (Walter 2002).

The 2003 fires had a substantial impact on the wild horse population of the Australian Alps, with a sharp decrease in the wild horse population size following the fires (Figure 2). After the fires, Walter (2003) indicated that when wild horse numbers were low, that there was great potential for the population to increase dramatically due to the increased availability of high quality food and reduced population pressure. This was demonstrated by the results of the 2009 aerial survey which showed that the population had increased by 224% since 2003 (Dawson 2009a). In a slightly different context, Catling (1991) predicted that wild horses would 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 have been reports of wild dogs chasing foals in the Victorian Alps (Walter 2002). Parasitism and disease may also be causes of mortality and/or reduced health. However, neither of these factors has been formally investigated or quantified.

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

3. Wild horse environmental impacts 3.1 Environmental impacts of wild horses

Australia's ecosystems have evolved without the grazing pressure and the physical impact of heavy, hard- hoofed animals (Carr & Turner 1959a; 1959b Ashton & Williams 1989; Green et al. 2006). Wild horse activity in the Victorian Alps represents a type and intensity of impact to which native ecosystems and their components are not adapted. The environmental impacts of wild horses are recognised by Victoria’s environment legislation with “degradation and loss of habitat caused by feral horses” listed as a threatening process under the Flora and Fauna Guarantee Act (1988).

The social and behavioural habits of wild horses as well as their physical characteristics (i.e. hard hooves, large size, 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 of these actions are summarised in Table 1.

Table 1: Summary of wild horse environmental impacts Element Impacts Australian Alps research General research Soil & substrate • Exposed soil surface; Dyring 1990 Berman & 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 composition Turner 1987 especially on wet soils; & Loydi & Zalba 2009 • creation of nutrient hotspots (especially nitrogen). Peatlands (also • Drying out of bogs & potential Dyring 1990 Rogers 1991, 1994 known as bogs or draining of entire bog systems; Whinam & Chilcott 2002 mossbeds) • creation of bare pavements; Whinam et al. 2003 • incision & soil erosion; Tolsma 2008a, 2008b • silt deposition downstream; • dominance of unpalatable species; & • loss of habitat for threatened species. Waterways • Degradation of stream function; Prober & Thiele 2007 Beever & Brussard 2000 (streams & • incision & channelling; Dyring 1990 Rogers 1991, 1994 streambanks) • soil compaction leading to decreased Whinam & Comfort 1996 infiltration; Whinam & Chilcott 2002 • increased downslope sedimentation; Prober & Theile 2007 • increased nutrient loads; Wild & Poll 2012 • lateral erosion; • streambank disturbance & slumping; • fouling of waterholes; & • changes in water flow & drainage patterns. Vegetation (& • Removal of native vegetation cover; Dyring 1990 Beever & Brussard 2000 communities) • dispersal of weed seeds; Whinam & Chilcott 2002 Beever et al. 2003 • changes to the vegetation structure Whinam & Comfort 1996 Beever et al. 2008 & species composition of the ground Whinam et al. 1994 Rogers 1991, 1994 stratum; Prober & Theile 2007 Turner 1987 • native tree mortality; Walter 2002 Loydi & Zalba 2009 • increase vulnerability of threatened McKay 2001 De Stoppelaire et al. 2004 vegetation; & Leigh et al. 1991 Bridle & Kirkpatrick 1999 • increased nutrient loads. Thomas 2010 Cambell & Gibson 2001 Wild & Poll 2012 Schott 2002

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

Native fauna • Competition for resources; Clemann et al. 2001 Berman & Jarman 1998 • altered food availability; Clemann 2002 Lenehan 2010 • habitat modification & loss; Brown et al. 2007 Zalba & Cossani 2009 • increased vulnerability of threatened Beever & Herrick 2006 species; & Beever et al. 2008 • competitive exclusion. Nano et al 2003

The degree of wild horse related degradation in the Victorian Alps will depend on:

• wild horse density; • timing (i.e. seasonality of grazing); • scale of activity (extent); • the resilience of the vegetation community; • topography – including slope; • soil type (i.e. fineness and/or wetness); • elevation; • the frequency and intensity of use; • climate; • effects of other sympatric species; and • recent weather; • the longer-term disturbance history of the site (Whinam et • local drainage; al. 1994; Beever et al. 2003; Beever et al. 2008). • access to suitable areas;

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 few studies have been undertaken to quantify these impacts. Research includes:

• Dyring (1990) conducted research on the effects of wild horses on sub-alpine and montane environments in Australia. Wild horse impacts on soils, vegetation and streams were quantified in four small catchments in the southern Snowy Mountains. Seasonal habitat usage and the abundance of wild horses were also investigated. Wild horses were found to either initiate or perpetuate changes in sub-alpine and montane environments. Rates of environmental change could not however be investigated 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 the effects of wild horse activity on grasslands and stream margins (Prober & Thiele 2007; Wild and Poll 2012). Exclosure plots, that prevent horses from accessing a defined area but allow access for other animals, were established at Cowombat Flat and Native Cat Flat. Detailed vegetation monitoring of these exclosure plots, as well as monitoring of stream bank condition, disturbance and erosion was undertaken in 1999, 2005 and 2012 (Prober & Thiele 2007; Wild and Poll 2012). The results show that changes to stream structure and function as a result of wild horses are clear and substantial, with significantly more incision and damage in the wild horse occupied area (outside the wild horse exclosures). Exclosure from horses has led to clear increases in vegetation height and increased litter cover (Wild and Poll 2012). The effect of wild horses on vegetation structure and composition was less consistent; however there was a trend for the recovery of dense swards of sedges and grasses associated with the competitive exclusion of some lower stature species inside horse exclosures (Wild and 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 individual mossbeds (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 by the Arthur Rylah Institute since 2004. The aims included: to assess the current state of sub-alpine mossbed communities, estimate potential threats to mossbeds and determine restoration and other management 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 activity

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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 great concern in the east Alps of Victoria. In the East Alps Unit of the ANP, 97% (63 of 65) of peatland systems were found to be impacted (i.e. compacted, trampled or pugged) by wild horses (Tolsma 2008b). • In 2011 the AALC commenced a project that aims to quantify the impacts of wild horses on upland streams and wetlands in the Australian Alps. The results of this study will be available in autumn 2013 and 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 a negative 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 rationale

Region Wild horse strategy Rationale for the plan (ecological) AANPs Kosciuszko National Park Horse The National Parks & Wildlife Service has legislative responsibility to Management Plan . protect native habitats & wildlife within its reserves & a responsibility to minimise the impact of introduced species, including wild horses. The 2006 Plan of Management called for a wild horse management plan & the exclusion of wild horses from key areas. (NSW NPWS 2008). Namadgi National Park Feral horse The plan aims to minimise the negative impact of wild horses including Management Plan . grazing on sensitive vegetation, trampling of streambanks, trail formation & erosion. These can lead to draining of entire bog systems, loss of habitat for threatened species & silt deposition downstream. (ACT Government 2007). National Guy Fawkes River National Park: The National Parks & Wildlife Service has legislative responsibility to Horse Management Plan . protect native habitats & wildlife within its reserves & a responsibility to minimise the impact of introduced species, including wild horses (NSW NPWS 2006a). Wild horses are an introduced species that have adverse impacts on Australian ecosystems with particularly severe consequences for native fauna & flora (English 2001). Feral horse Management Plan for Wild horses have been identified as posing a threat to the conservation Oxley Wild Rivers National Park values of the park & water quality. (NSW NPWS 2006b). Protecting the natural & cultural Queensland Parks & Wildlife Service has a legal obligation to conserve values of Carnavon National Park: & protect the natural values of Canarvon NP & control threatening A plan to manage wild horses & processes caused by pest species including wild horses. Destructive other pest animals impacts by wild horses have led to: the deterioration of aquatic ecosystems & serious landscape dysfunction (losses in biomass, accelerated erosion, soil compaction, altered species composition & vegetation structure & altered fire ecology). (Weaver 2007). New Kaimanawa Wild Horses Plan. Horses have been shown to adversely affect nationally significant Zealand ecological values. There is a need to eliminate the impacts of horses on important conservation values. (DOC 2006).

In addition to these wild horse plans and strategies, a series of workshops on wild horse impact and management in the Australian Alps (see: Walters & Hallam 1993; O’Brien & Solomon 2004) and a national workshop (see: Dawson et al . 2006) have demonstrated widespread concern from scientists and practitioners about 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 of the Victorian Alps is considered below in greater detail.

3.2 Impacts on soil and substrate

It is generally accepted that alpine areas are more susceptible to damage by hard hooved animals such as wild horses than most other environments, due to their wet fragile soils and slow vegetation growth rates (Whinam et al. 1994). Wild horse trampling and grazing can lead to major changes to the soil, including: pugging, drying,

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

compaction 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 cause localised 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 produce extensive track networks in the Australian Alps. Continual trampling by wild horses can increase soil compaction and therefore reduce aeration and pore space of soils and subsequently decrease water infiltration 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 matter inputs, 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 penetration resistance (a measure of soil compaction) in the soil surfaces of sites without wild horses (compared to those with wild horses).

Photo 1 : Trampled area at Cowombat Flat (source: Arn Tolsma 2008).

Photo 2 : Wild horse camp, Davies Plain (Source: Arn Tolsma 2008)

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

Photo 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 (averaging between 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. Compaction was found to be most severe on dry soils, where 20-50 passes by wild horses resulted in significantly compacted soils. Compaction was found not to increase substantially with subsequent passes. Therefore an average group of four wild horses using a new track twice daily for less than a week will result in significant compaction. Wild horses were found to have similar usage of sub-alpine and montane areas, with no difference 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 has substantial immediate as well as delayed effects on the soils of shrubland, herbfield and bolster heath communities, however effects on dry grassland soils were less evident. Wild horse exclosure experiments in the eastern Victorian Alps have shown that continued grazing and trampling by wild horses has maintained low herbfield turfs, where the soil surface is more susceptible to trampling impacts than the grasslands found in the 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 damage than dry soils. This is supported by Rogers (1994) who demonstrated that dry areas are more resistant to fracturing than wet areas, which were more easily broken up by trampling. The loss of soil structural composition 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 downslope sedimentation, water ponding, and opportunities for the establishment of weeds (Rogers 1994). The gradient of the slope has been found in other studies to directly correspond to the level of erosion. The steeper the slope 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 increase the exposure of soils to the elements (such as wind, rain and needle ice), leads to the removal of vegetation and 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). Wild horses caused considerable erosion in a sandy environment in the USA: over a five to seven year period fenced plots (excluding horses) were on average 0.63 m higher than unfenced plots in sand dunes habitats (De Stoppelaire et al. 2004).

Pugging of soil (trampling of wet soils leaving a dense mat of deep footprints), in particular around wetlands and waterways, can change soil nutrient status, and increase water turbidity and sediment loads in adjacent waterways (O’Connor 2005). Dyring (1990) found that wild horses in the Australian Alps can create nutrient

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

hotspots due to the high levels of nutrients (especially nitrogen) in their dung and urine. Manure in dung piles increases the availability of soil nutrients, especially nitrogen and phosphorous, thus creating microhabitats suitable for weed invasion (Loydi & Zalba 2009). 3.3 Impacts on vegetation

The 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 vegetation is a reduction in vegetation cover and height, however they may also alter plant species composition, richness and diversity, and contribute to weed invasion (Turner 1987; Dyring 1990; Rogers 1991; Beever & Brussard 2000; De Stoppelaire et al. 2004; Loydi & Zalba 2008; Wild and Poll 2012). Trampling by wild horses also alters vegetation, 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 wallowing

Vertebrate 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 introduced herbivores 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) in their 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 of natives herbivores and rabbits alone (Bridle & Kirkpatrick 1999).

McKay (2001) conducted a survey of the impacts of horse-riding and walking on the alpine vegetation of Mount Bogong. Trampling was found to reduce the height, cover and abundance of both shrub and ground flora within track areas and to result in greater exposure of bare ground. Beever et al. (2008) argue that the loss 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 that horse trampling and grazing has resulted in the removal of vegetation and increased bare ground in horse occupied areas (Wild & Poll 2012). In contrast, fenced horse exclosure plots showed a trend for increasing vegetation cover and decreasing bare ground as they recovered from past horse disturbance over a thirteen year period (ibid ).

It is argued that grazing may have an impact on the reproductive success of some flora species by impacting on the dispersal opportunities of wind-dispersed species as well as their ability to attract pollinators; both of these functions are affected by flower height (Bridle & Kirkpatrick 1999). For example, on the Assateague Barrier Island (USA), a small herbaceous annual, Amaranthus pumilus was once abundant and is now limited to a 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. In Australia, clipping experiments on alpine herbs have shown that flowering success may be retarded if plants are 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 structure

Grazing by introduced herbivores can alter the appearance, productivity and composition of vegetation communities (Dyring 1990; Hobbs & Hyeneke 1992). This may be due to reduced regeneration/recruitment as a direct result of selective grazing or the physical impacts of trampling and erosion. Wild horses selectively graze palatable species and have the potential to change the composition of threatened vegetation

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

communities (Dyring 1990). Redistribution of nutrients through dung can also contribute to the changes in vegetation 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 the persistence of less vigorous species (Hobbs & Hyeneke 1992).

Dyring (1990) found trampled sites (and areas adjacent to track systems) had lower native plant diversity and a higher abundance of exotic species. Plants found on wild horse tracks were characteristically non-woody prostrate fast-growing annuals and grasses, with hemicryptophitic life-forms (species with renewal buds near the surface), which tolerated trampling better than upright plants (Dyring 1990). Similarly, horse occupied sites at Cowombat Flat and Native Cat Flat exhibited a predominance of hemicryptophitic species in contrast to horse exclosure plots, which were dominated by grasses and sedges (Wild & Poll 2012). Grasslands are more resilient to the impact of wild horses than other communities where ferns, mosses and shrubs are important components of the vegetation (Whinam et al. 1994; Venn et al. 2009). Whinam and Chilott (1999) found that shrubs and shrubland communities were more vulnerable to trampling than other life-forms or vegetation types in central Tasmanian alpine vegetation.

As well as affecting vegetation community composition, wild horse activity can affect the physical structure of vegetation communities. Exclosure experiments have shown that vegetation cover and height is far greater in horse 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, the following 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 exclusion of 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 of horses on vegetation height, plots inside horse exclosures were often characterised by dense swards of sedges and grasses associated with the competitive exclusion of some lower stature species (Wild & 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 ). Wild and Poll (2012) suggest that the resurgence of dense sedges and grasses and competitive exclusion of some lower stature species may indicate restoration 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 species richness as well as alter the species composition and structure of the vegetation (by increasing the predominance 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 series of monitoring and exclosure plots in the Kaimanawa Mountains, New Zealand, Rogers (1991; 1994), found that wild horses severely disrupted the composition of the native vegetation. In the grazed plots, species biomass and stature was low for all potentially taller, palatable grasses (Rogers 1991).

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

Photo 4: Cowombat Flat wild horse exclusion plots from the air (source: Geoff Robinson).

3.3.3 Threatened vegetation

In the Victorian Alps, wild horses are considered to be one of the major threats to alpine ecosystems (Tolsma 2008b). Wild horses are considered to be a serious threat to at least five plant communities listed in the Victorian 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 FFG Act. 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 listed alpine 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 by trampling, or their regeneration disrupted (McDougall 1982; McDougall & Walsh 2007). Similarly, the Alpine Snowpatch Community, situated on steep sheltered slopes, is subject to constant irrigation during the thaw which 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 in the 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 Biodiversity Conservation Act 1999 (EPBC) and/or the Victorian FFG Act 1988, and that are potentially at risk from wild horses, are presented in Appendix 2.

In order to mitigate the threat that wild horses pose to threatened flora species in the Victorian Alps, Parks Victoria has established three wild horse exclusion fences around particularly threatened and sensitive

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

communities. In 2002 two wild horse exclusion fences were established on Davies Plain around sub-alpine bogs known to contain several threatened plant species and the threatened Alpine Water Skink. In 2010 an exclusion 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 their habitat 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 encouragement

Wild horses can facilitate weed invasion through dispersal and the creation of a favourable environment for weeds 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). Therefore wild horses have the potential to disperse weeds both long and short distances and can subsequently contribute to the establishment of weed species across several spatial scales (Nimmo & Miller 2007). Weaver and Adams (1996) argue that within their home range, horses are a potentially significant vector in the dispersal of a range of weed species.

While wild horses are less likely than domestic horses (i.e. recreational riding horses or horses illegally released into the region) to introduce new weeds into the Victorian Alps, there is potential for this to occur, especially considering their increasing range and the potential for wild horses to occur across tenures (i.e. farms, state forests and national park). Many species of seed are transported in the dung of wild horses. Dung can be a source of viable seed taxa not otherwise found in a community (Campbell & Gibson 2001). Campbell and Gibson (2001) found that horses pass large numbers of seeds through their digestive tract generally within 48hours of consumption (but sometimes longer), and many of these seeds remain viable (Weaver & Adams 1996). 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 native vegetation along horse-riding tracks in three national parks in Victoria (including the ANP). Twenty-nine species of weeds were found to be dispersed via horse manure.

Wild horse disturbance (i.e. dung, soil disturbance and pugging) can provide favourable environmental conditions for the germination and colonisation of weed species (Dyring 1990; Rogers 1991; Loydi & Zalba 2009). Wild horse dung can result in significant changes in vegetation and can introduce and encourage some invasive weed species that could eventually colonise more pristine areas (Loydi & Zalba 2009). Nutrients in dung can favour weed establishment, with weeds establishing more vigorously in areas both trampled and subject to deposition of dung. In a study of the potential for horse dung to act as an invasion window in montane pampas grasslands, Loydi and Zalba (2009) found that the cover of introduced species was higher in dung piles than in control plots. Dyring (1990) speculated that the redistribution of nutrients through uneven

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

dung deposits and selective grazing would lead to exotic plants such as White Clover ( Trifolium repens) and Cats Ears ( Hypochoeris radicata ), which readily colonise dung and disturbed areas, becoming established in disturbed grassland and healthlands.

Wild horse disturbance was found to enhance the spread of smothering weeds in New Zealand’s Kaimanawa Mountains (Rogers 1991; 1994). In the Australian Alps, exotic species were found to colonise the disturbed area 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 Yorkshire fog grass (Holcus lanatus , an invasive grass species native to Europe) and red fescue grass ( Festuca rubra , an exotic 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 2010 unpublished report) Thomas (2010) made a series of assessments regarding wild horses and their relationship with 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 Track appeared to be associated with wild horses; • there was evidence of wild horses grazing on Brown top bent grass ( Agrostis capillaris ), which may be aiding the spread of this weed; and • wild horses appear to avoid Yorkshire fog grass ( Holcus Ianatus ), providing this species with a competitive advantage.

3.3.5 Native tree mortality

Wild horses have been found to affect native tree mortality in Australia. The chewing and stripping of bark by horses can reduce regeneration of seedlings and may result in the death of mature trees. A significant negative relationship was found between bark chewing damage and overall tree health in Guy Fawkes River National Park (Schott 2002). Impact assessments identified bark-chewing damage was most severe along drainage-lines and in close proximity with other water sources that are heavily used by wild horses. Schott (2002) found that wild 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 the south-east corner of the mainland (Tolsma 2008b). “Alpine Sphagnum bogs and associated fens” are listed as an endangered ecological community under federal legislation (Environmental Protection and Biodiversity Conservation Act 1999). Alpine bogs are also protected by Victorian legislation, where they are listed as a threatened community under the Flora and Fauna Guarantee Act (1988). These ecosystems are of national importance 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 regulation of 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 horses are known to have a detrimental impact on Sphagnum growth and integrity, with the resulting vegetation loss ultimately leading to degradation of this ecological community (Dyring 1990; TSSC 2009). Wild horses are therefore a major threat to Alpine Sphagnum peatland communities (Whinam & Chilcott 2002; Tolsma 2008b; TSSC 2009; DEWHA 2009a).

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

Bogs and peatlands are highly sensitive to damage by trampling and grazing. Preferential grazing of palatable herbs and grasses in Sphagnum bogs, combined with browsing of new growth of shrubs can lead to increased dominance by unpalatable species (Whinam & Chilcott 2002). Sphagnum is easily crushed and broken up by wild horses trampling the delicate vegetation, selectively grazing and wallowing in pools and waterways (TSSC 2009). Trampling may lead to the drying out of bogs, the loss of Sphagnum cover as well as changes to other vegetation, 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 trampling and grazing, irrespective of local variations in horse density and habitat abundance (Rogers 1991). The vulnerability of bogs in New Zealand was also found to increase with wetness (Rogers 1991). Whinam and Chilcott (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 the status of peatland systems in the Victorian Alps was investigated by Tolsma (2008a; 2008b). In the East Alps Unit of the ANP, 97% (n=63) of peatland systems were found to be impacted (i.e. compacted, trampled or pugged) by wild horses (Tolsma 2008b). Only two peatlands assessed by Tolsma (2008b) in this unit of the ANP did not show any signs of current wild horse activity: a fenced peatland at Davies Plain and an isolated system on the south-east edge of the Unit. Whinam and Chilcott (2002) argue that wild horses are one of the greatest threats to the survival of peatlands.

Channelling is a form of erosion and water diversion which can result from wild horse activity. Trampling and wallowing cause channels to form in the disturbed Sphagnum. Channelling leads to changes in water flow, as water exits the disturbed bog more rapidly. This action may completely alter the drainage pattern and result in drier conditions (Whinam & Chilcott 2002; TSSC 2009). The formation of channels is detrimental to the fens associated 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 (primarily in the 2003 fires) Tolsma (2008b) found that wild horse activity in burnt sub-alpine to alpine peatlands in the Victorian Alps varied from minor trampling at peatland margins to extensive pugging across almost the entire burnt peatland surface. On average, 25% of all peatland surface area assessed in the East Alps Unit of the ANP and 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, and may impact on some peatlands where restoration work is occurring (Tolsma 2008b). Tolsma (2008b) argues that in the Victorian Alps, many areas of burnt peatland, particularly in the East Alps Unit, are unlikely to completely 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 Alpine Sphagnum 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 wild horses.

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The Ecology of Wild Horses and their Environmental Impact in the Victorian Alps May 2013

Photo 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 and productivity (Dawson 2009b), but are typically fragile and susceptible to damage by wild horses (and other large 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; NPWS 2007; Prober & Thiele 2007; Dawson 2010). Streambanks are easily churned up and broken down by wild horse hooves sinking into wet soils (Dyring 1990). Grazing by large hard-hooved herbivores can affect streamside vegetation, stream channel morphology, shape and quality of the water column and the structure of 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 bank slumping and breakdown, vegetation disturbance and increased soil compaction (see Photos 7, 8 and 9). This can 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 stream function and structure as a result of wild horse exclosure fencing. The unfenced stream areas had more bare ground, were more entrenched and had distinct, open water channels, whereas areas within the exclosures had indistinct channels, a more or less complete vegetation cover across the channel and no or little visible open water (Prober & Thiele 2007, Wild & Poll 2012). There was a significant increase in stream depth over time in unfenced plots at Native Cat Flat while stream depth within the exclosures remained stable, suggesting accelerated erosion in horse occupied areas (Wild & Poll 2012). Stream condition was better and consistently improved over time in the horse exclosure plots which exhibited less pugging, stream slumping (collapse of the stream bank) and bare ground than unfenced areas (Wild & Poll 2012). The extra vegetation and lack of bare ground 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 to faster flows and accelerated erosion of the stream channel, particularly at native Cat Flat where steep banks with 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 on stream and catchment hydrology and water quality.

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In 2011 the AALC commenced a project that aims to quantify the impacts of wild horses on upland streams and wetlands in the Australian Alps. The results of this study will be available in autumn 2013 and will provide further 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).

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3.6 Impacts on fauna

Wild horse populations can alter the composition of bird, fish, crustacean, small mammal, reptile and ant communities (Nimmo & Miller 2007) and have been identified as a major threat to a range of native wildlife species in the Victorian Alps. The 2001 AALC Natural Heritage Working Group Workshop of field staff and scientists, 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 competition for resources (i.e. food, water, shelter and space) (Olsen & Low 2006; Nimmo & Miller 2007).

3.6.1 Competition and altered food availability

Wild horses compete for resources with native herbivores, especially macropods, including: grey kangaroos (Macropus giganteus ), red-necked wallabies ( M.rufogriseus ) and swamp wallabies ( Wallabia bicolour ). Various studies 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 by wild horses. A study of wild horse impacts in Guy Fawkes River National Park by Lenehan (2010) provides evidence of wild horses displacing kangaroos from prime feeding habitats. Dung transects conducted in the national park showed a strong negative relationship between wild horse dung and macropod dung. As wild horses were removed from the transect area (as part of NSW National Parks and Wildlife Service (NPWS) horse capture program, where 250 wild horses were removed) there was a significant progressive decline in horse dung and increase in macropod dung. Indicating that macropods were responding positively to decreases in horse abundance (Lenehan 2010).

Although it has not been investigated to date, it is possible that wild horses also compete with other native mammals such as wombats ( Vombatus ursinus ). Wombats also feed primarily on grasses (such as Poa and other grass species and some shrubs) and like wild horses, dig below the snow to reach low vegetation during winter (Matthews 2010).

Wild horse activity may constrain resources for many species and may increase the vulnerability of threatened species (Nano et al. 2003). A reduction in the density of wild horses in Finke Gorge National Park and surrounding area correlated with a striking increase in black-footed rock wallabies ( Petrogale lateralis ) and small fauna populations (Matthews et al. 2001). In 1990 no fresh black-footed rock wallaby dung was recorded, however after approximately 6000 wild horses were removed (and the population kept at low numbers), the amount of fresh dung recorded steadily increased over the following ten years. It is suggested that the wild horse population may also have suppressed the endangered stick-nest rat ( Zyzomys pedunculatus ) in the West MacDonald ranges (Nano et al. 2003). Despite numerous surveys the species was not recorded between 1960 and 1996 and it was concluded the species was extinct. However in 1996 it was rediscovered at numerous sites, a finding that corresponded with the removal of 30 000 wild horses (Nano et al. 2003). The major food plants identified in the diet of the stick-nest rat were also palatable to wild horses and other introduced ungulates ( ibid. ).

3.6.2 Habitat modification

Wild horse grazing can result in a more open shrubland and increased area of bare ground, which in turn causes 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 habitat value of a site for animal species that require shrubs for shade, food or protection from predators and other threats 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 opportunities for 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 in

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Argentina. The presence of wild horses was associated with an increase in the rate of egg predation, which varied from 12.5% within exclosures to 70% in grazed areas. This was directly related to increased visibility of the nests and subsequent exposure to predators, nest trampling and reduced nesting sites. In Victoria’s Barmah Forest wild horses are listed as a threat to some ground nesting birds including the Australasian Bittern and Little Bittern (SAC 1997a; 1997b). Due to a lack of research it is unknown if wild horses pose a threat to any birds in the Victorian Alps.

Wild horses may potentially cause the collapse of wildlife burrows (Theile & Prober 1999a). In the Victorian Alps many medium and small mammals, such as the bush rat ( Rattus fuscipes ), swamp rat ( R. lutreolus ) and broad-tooothed rat ( Mastacomys fuscus ), use burrows that may be susceptible to trampling damage. Wombat burrows that, for example are dug in open ground with little protective cover over the burrow may be susceptible to damage by wild horses. In the USA, exclosure plots around springs exhibited more small- mammal burrow 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 currently unknown. Beever and Herrick (2006) found a greater abundance of ant mounds in sites where wild horses had been removed over ten years ago. This may have a substantial influence on ecosystem health and the survival of other species.

Extensive damage to the structural complexity of ground-level vegetation and habitat caused by wild horses threatens the reptile and amphibian species of the Victorian Alps. Structural complexity of habitat is a critical requirement for many reptile species and communities (Clemann et al. 2001). Litter cover, ground cover and the 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 vegetation along 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 affects habitat complexity through: direct removal of vegetation; destruction of structural components in the ground layer; 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 ) are threatened by wild horse impacts on peatlands, wet heath and riparian areas, which provide vital habitat for these 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 has immediate effects on habitat structure, and leads to hydrological consequences such as deteriorating water quality and loss of landscape structure. Damage to habitat caused by wild horses is specifically identified as a threat to the federally endangered alpine she-oak skink, which occurs in close proximity to bogs, streams and wet heaths. Recommended actions to mitigate this threat include the development and implementation of a management plan for the control of wild horses (DEWHA 2009b).

Historically, the threatened alpine tree frog ( Litoria verreauxii alpine ) was widespread and abundant across most of the high country of mainland south-eastern Australia (Clemann & Gillespie 2004). The species has since retracted from much of its previous habitat. Populations of the alpine tree frog are known to be subject to a number of threatening processes, including the trampling of habitat by wild horses (Clemann & Gillespie 2004). 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 through alteration 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 in mammalian 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 after

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the removal of cattle (Legge et al. 2007). In a study of horse impacts using exclosures in the USA, qualitative differences 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 vegetation structure is associated with habitat quality for these species (Carron 1985). The habitat of small mammals in Alpine regions is extremely sensitive and threatened by climate change (Green et al. 2008). A species of particular 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). The broad-toothed rat inhabits areas of moderate-to-dense grass and/or sedge cover (Green et al. 2008). This environment is favoured by wild horses for grazing and the habitat can be broken-up through wild horse activity. O’Brien et al. (2008) found populations of broad-toothed rats that existed in isolated patches were likely to suffer local extinction due to low levels of success emigrating through unsuitable habitat to reach suitable habitat.

3.6.3 Threatened fauna in the Victorian Alps

Herpetofauna (reptiles and frogs) are central components of the vertebrate fauna of the Victorian Alps and several threatened species are endemic to alpine areas (Clemann et al. 2001). A large proportion of this group are officially listed as threatened at the federal and state level (Appendix 3). Herpetofauna in this region are generally 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 threatening these species (Clemann et al. 2001). For example, the alpine water skink (Eulamprus kosciuskoi ) (photo 10) is listed 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 in good condition (i.e. high cover of live Sphagnum and low cover of bare-ground, rock and non-mossbed vegetation). Any threat to Sphagnum cover, such as that posed by wild horse grazing and trampling, severely threatens the habitat of the alpine water skink (Steane et al. 2005). Horses have impacted much habitat that was 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 horse exclusion 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 threatened by wild horses (Source: Nick Clemann).

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4. Wild horse biosecurity issues Wild horses are a prominent reservoir for exotic and endemic diseases and parasites that can affect native wildlife, domestic horses, stock and humans (Bradshaw et al. 2007). The spread of pests and disease by feral animals 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 and transmitting disease. Diseases of concern are either those that have the potential to establish or exist already within Australia. Diseases are highly variable, for example they may be equine specific or they may affect several species, transmissibility varies, and symptoms range from minor ailments to mortality. The wild horse population in the Australian Alps poses a potential risk to other species that may co-habit with them such as native 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 the disease 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 of vertebrate 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 in places such as Grey Mare in Kosciusko National Park and keeping them fungus free is a critical biodiversity priority.

Wild horses can play a potential role in a disease outbreak of a newly imported disease (Biosecurity Australia 2009). There are many steps involved in the outbreak of a new disease. Wild horses must first be exposed to the disease, once exposure occurs, a range of outbreak scenarios are possible from no spread to widespread establishment. Outbreak scenarios are dependent on the epidemiology of each disease agent. The role that wild horses play in a potential disease outbreak scenario for a newly imported disease was considered in a risk assessment by Biosecurity Australia (2009). In general, wild horses were thought to have a limited ability to affect domestic horse populations because of their remoteness. Equine Influenza received the highest risk assessment (moderate). There was an outbreak of Equine Influenza in 2007, which led to prohibitions on horse movements in Victoria to control the spread of the disease, however, it was eliminated (Animal Health Australia 2009).

There is little known about the incidence and prevalence of many existing diseases of domestic horses in Australia, and much less is known about the frequency of disease in wild horses. There are a range of zoonotic diseases (diseases that horses can share with humans and other livestock) which are present in Australia and may 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 affect native species.

Hendra virus is a relatively new and emerging disease, first reported in 1994 in Queensland (Equine Species Working Group n.d). Subsequently there is not a great deal known about the disease, however, horses are likely to be dead-end hosts. It causes severe respiratory illness in horses and is frequently fatal. Humans can contract the disease if they have direct contact with blood or saliva of an infected horse (Equine Species Working Group n.d).

Murray Valley Encephalitis is a virus spread by mosquitoes that can infect many animals, including horses and humans (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 widespread outbreak infected domestic horses in north and north western Victoria (DPI 2012).

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Humans, domestic animals and wildlife are susceptible to the bacterial disease Leptospirosis and infected animals may become sick or show no symptoms at all (Equine Species Working Group n.d). Salmonellosis is a bacterial disease that can infect horses and humans and is of concern because some strains exhibit resistance to 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 rabies in Australia; however, there have been no reports of horses being affected by this disease. Tetanus can be a fatal disease and its spores are widely distributed, usually in soil, dust and manure; horses and humans are the most susceptible of all of the animal species to tetanus (Equine Species Working Group n.d). Ringworm is a fungal skin disease. Numerous species can transmit ringworm to humans (Equine Species Working Group n.d).

5. Gaps in knowledge There has been a limited amount of research into wild horse biology, behaviour and ecological impacts in the Alpine region to-date. An important area for investigation that will aid in guiding effective management is the relationship between wild horse density and damage (Dawson et al. 2006). Quantification of the relationship between density, impact and population control has been identified as a priority research area for the management of wild horses by the AALC. The AALC has initiated a project that aims to address this gap by developing a protocol for determining horse density at the local scale and investigating the influence of horse density on impacts. Site-specific research using experimental trials to determine local levels of resistance to impact 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 are likely to significantly under-estimate the total population size. There are large areas known to be occupied by wild horses that have been excluded from previous aerial surveys, including Byadbo and adjoining areas of the Alpine National Park and adjacent State Forests (Dawson 2009). There are plans to cover a larger portion of the area occupied by wild horse in future aerial population surveys in order to obtain a more accurate estimate of the total Victorian Alps wild horse population size. Wild horses do not currently occupy all suitable habitat within the Victorian Alps. Mapping potential horse habitat that could potentially be colonised by wild horses is required 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 have not been investigated at a broad spatial scale. The effects of chronic disturbance over broader areas is subsequently 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 been considered. These studies are important; however they may not be representative of the Victorian Alps system more 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 through time as the environment varies (e.g. drought, fire, climate change etc). The environmental impact of wild horses may be exacerbated in drought years, as they tend to concentrate around watering points (Dawson 2010). Impacts are also likely to increase substantially after fire (such as those that occurred in Victoria in 2003 and 2006/07) when Alpine environments such as peatlands are particularly susceptible. Climate change is likely to influence the magnitude of the impacts of wild horses in future years. Alpine species and communities are amongst the most vulnerable to the effects of climate change and therefore their resilience to climate change requires that they be protected and maintained in as healthy a condition as possible (DSE 2010). This pressure combined with the impact of wild horses requires further investigation.

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Appendix 1: Officially listed plant ecological communities at risk of severe damage from wild horse activity Floristic Community or Ecological Vegetation Class EPBC FFG Main consequences Alpine Bog Community Endangered* Listed Disruption of plant regeneration, selective grazing leading to compositional changes, weed invasion, severe trampling, soil loss, and loss of hydrological function. Fen (Bog Pool) Community Endangered* Listed Disruption of plant regeneration, selective grazing leading to compositional changes, weed invasion, severe trampling, and loss of hydrological function. Alpine Snowpatch Listed Severe trampling, soil loss, displacement of Community vegetation, weed invasion, selective grazing leading to compositional changes. Caltha introloba Herbland Listed Soil loss, displacement of vegetation, weed Community invasion Montane Swamp Complex Listed Severe trampling, soil loss, displacement of Community vegetation, weed invasion, smothering by dung piles, selective grazing leading to compositional changes. * Alpine Bog and Fen Pool communities are combined in the EPBC listing

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Appendix 2: FFG-listed and EPBC-listed plant species potentially at risk from wild horse activity in the eastern Victorian Alps AROT = Australian Rare or Threatened status, VROT = Victorian Rare or Threatened status. e = endangered (Victoria), r =- rare (Victoria), v = vulnerable (Victoria), V = Vulnerable (EPBC, Australia). AROT, Species Listed VROT Main consequences Bogong Eyebright ( Euphrasia FFG, V, v May be selectively grazed - more common in ungrazed open heath eichleri ) EPBC & grassland. Snow Pratia ( Lobelia gelida ) FFG, V, v Trampling & loss of habitat - ephemeral pools in wet alpine EPBC grasslands & creek margins Austral Toad-flax ( Thesium FFG, V, v Trampling of habitat - grasslands & grassy woodlands. Considered australe ) EPBC to be palatable to stock. Tasmanian Bladderwort FFG v Trampling & loss of habitat - Caltha introloba Herbland Community (Utricularia monanthos ) & stream edges Allied Bent-grass ( Deyeuxia FFG e Trampling & loss of habitat - Caltha introloba Herbland Community affinis ) Cushion Rush ( Juncus FFG v Trampling & loss of habitat - Caltha introloba Herbland antarcticus ) Community, Alpine Snowpatch Community & bog margins Rock Poa ( Poa saxicola ) FFG v Trampling & loss of habitat - Alpine Snowpatch Community, open heath & grassland. Palatable, & rare in grazed areas. Marsh Leek-orchid FFG e Trampling & loss of habitat - alpine wet heathlands & bogs. (Prasophyllum niphopedium ) Observed to be directly impacted. Mountain Daisy ( Brachyscome FFG v Trampling & loss of habitat - alpine wet grasslands & herbfields sp. 3 ) Slender Parrot-pea ( Almaleea FFG v Trampling of habitat - sub-alpine heathlands & stream fringes capitata ) Wire-head Sedge ( Carex FFG v Trampling & loss of habitat - alpine herbfields cephalotes ) Bogong Apple-moss FFG e Trampling & loss of habitat - wet grasslands & bog margins (Bartramia subsymmetrica ) Austral Moonwort FFG v Trampling & loss of habitat - subalpine grassland & margins of bogs (Botrychium australe ) & streams. Intolerant of disturbance. Rough Eyebright ( Euphrasia FFG e Trampling & loss of habitat - grassy edges of wetlands scabra ) Felted Buttercup ( Ranunculus v Trampling & loss of habitat - alpine herbfields, wet grasslands & muelleri ) bog margins. Observed to be directly impacted. Olive Mallee ( Eucalyptus v Trampling of habitat - sub-alpine woodlands. Observed to be elaeophloia ) directly impacted. Star Sedge ( Carex echinata ) v Trampling & loss of habitat - alpine wet heathlands & bogs Snow Wort ( Abrotenella v Trampling & loss of habitat - alpine wet heathlands, bogs & moist nivigena ) herbfields Alpine Marsh Marigold r Trampling & loss of habitat - Caltha introloba Herbland Community (Psychrophila introloba ) Carpet Sedge ( Carex jackiana ) r Trampling & loss of habitat - moist alpine herbfields Turquoise Coprosma r Trampling of habitat - alpine wet heathlands, bogs & grasslands (Coprosma moorei ) Dwarf Coprosma ( Coprosma e Trampling of habitat - alpine woodlands, heathlands & grasslands pumila ) Snow Pennywort ( Diplaspis r Trampling of habitat - alpine wet heathlands, bogs, grasslands & nivis ) herbfields Sky Lily ( Herpolirion novae- r Trampling & loss of habitat - alpine wet heathlands, bogs & zelandiae ) herbfields Tuft-rush ( Oreobolus r Trampling & loss of habitat - alpine wet heathlands & bogs oxycarpus subsp. oxycarpus ) Alpine Tuft-rush ( Oreobolus r Trampling & loss of habitat - alpine wet heathlands & bogs pumilo subsp. pumilio ) Parantennaria ( Parantennaria v Trampling & loss of habitat - Caltha introloba Herbland Community uniceps ) Snow Aciphyll ( Aciphylla r Selective grazing in open heath & grassland. Highly palatable & glacialis ) most common in ungrazed areas.

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Mountain Aciphyll ( Aciphylla r Selectively grazed in grasslands & bog margins. Highly palatable, simplicifolia ) most common in ungrazed areas. Native Wintercress ( Barbarea v Trampling & loss of habitat - bogs & stream margins. Highly grayi ) palatable to stock. Grassy Moonwort v Trampling of grassy habitat. Intolerant of disturbance. (Botrychium lunaria ) Baw Baw Daisy ( Brachyscome r Trampling & loss of habitat - alpine wet heathlands & bogs obovata ) Marsh Daisy ( Brachyscome r Trampling & loss of habitat - alpine wet heathlands & bogs. radicans ) Spreading Bitter-cress v Trampling of habitat - wet grasslands and bog margins. Palatable (Cardamine astoniae ) to 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 ( Climacium v Physical damage to habitat - within streams dendroides ) Creeping Coprosma r Trampling & loss of habitat - alpine wet heathlands & bogs. (Coprosma perpusilla ) White Billy-buttons v Trampling & damage to habitat - Caltha herbfields & valley (Craspedia alba ) bottoms. Palatable to stock. Tufted Hair-grass r Trampling & loss of habitat - Caltha introloba Herbland Community (Deschampsia caespitosa ) & fens Skirted Bent-grass ( Deyeuxia v Trampling & loss of habitat - alpine wet heathlands & bogs. talariata ) Tailed Eyebright ( Euphrasia r Trampling & loss of habitat - Alpine Sphagnum bogs caudata ) Slender Gingidia ( Gingidia v Trampling & loss of habitat - stream margins. Highly palatable, harveyana ) hence selectively grazed. Alpine Holy-grass ( Hierochloe v Trampling & loss of habitat - alpine wet heathlands & bogs. submutica ) Tussock Woodrush ( Luzula r Trampling & loss of habitat - grassy edges of wetlands alpestris ) Slender Woodrush ( Luzula v Trampling & loss of habitat - damp grasslands atrata ) Spreading Clubmoss r Trampling & loss of habitat - alpine wet heathlands & bogs. (Lycopodium scariosum ) Hump Moss ( Meesia muelleri ) r Trampling & loss of habitat - boggy grasslands Branched Caraway v Selective grazing in rocky habitat. Palatable, and now extremely (Oreomyrrhis brevipes ) rare in grazed areas. Wedge Oschatzia ( Oschatzia r Trampling & loss of habitat - alpine wet heathlands and bogs. cuneifolia ) Matted Rice-flower ( Pimelea r Possible selective grazing in open heath & grassland. Rare in biflora ) grazed areas. Hard-head Bush-pea r Trampling & loss of habitat - margins of alpine wet heathlands (Pultenaea capitellata ) Southern Sheep-grass e Trampling & loss of habitat - Caltha introloba Herbland Community (Rytidosperma australe )

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Appendix 3: Officially listed or threatened fauna species potentially at risk from feral horse activity in the eastern Victorian Alps Species EPBC FFG DSE 2 Main consequences Alpine Water Skink Listed Critically Loss and degradation of habitat - alpine bog (Eulamprus kosciuskoi ) Endangered and alpine fen (bog pool) communities Alpine Bog Skink Listed Endangered Loss and degradation of habitat - alpine bog (Pseudomoia cryodroma ) and alpine fen (bog pool) communities, woodlands and heathlands Alpine She-oak Skink Endangered Listed Endangered Loss and degradation of habitat - alpine (Cyclodomorphus tussock grasslands, alpine low heathlands praealtus ) Guthega Skink ( Liopholis Under Listed Critically Loss and degradation of habitat - alpine guthega ) consideration Endangered heathlands Mountain Skink ( Liopholis Data Deficient Loss and degradation of habitat - alpine Montana ) woodlands Alpine Tree Frog ( Litoria Vulnerable Listed Critically Loss and degradation of habitat - alpine and verreauxii alpina ) Endangered subalpine wetlands, riparian zones and ephemeral pools.

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