Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria

Final report

Dr Arn Tolsma & Dr James Shannon

January 2018

Client Report for Parks Victoria Photo credit Horse droppings and bare ground around very old Snowgums, approximately 2 km south of Mt Jim, Bogong High Plains, Victoria. Photo by James Shannon.

© The State of Victoria Department of Environment, Land, Water and Planning 2018 This work is licensed under a Creative Commons Attribution 4.0 International licence. You are free to re-use the work under that licence, on the condition that you credit the State of Victoria as author. The licence does not apply to any images, photographs or branding, including the Victorian Coat of Arms, the Victorian Government logo and the Department of Environment, Land, Water and Planning (DELWP) logo. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/

Disclaimer This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. Accessibility If you would like to receive this publication in an alternative format, please telephone the DELWP Customer Service Centre on 136186, email [email protected], or via the National Relay Service on 133 677 www.relayservice.com.au. This document is also available on the internet at www.delwp.vic.gov.au. Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria

Final report

Dr Arn Tolsma1 & Dr James Shannon2

1Arthur Rylah Institute for Environmental Research Department of Environment, Land, Water and Planning Heidelberg, Victoria 2Consultant

January 2018

Client report for Parks Victoria Acknowledgements This research was initiated by John Wright and Marie Keatley (Parks Victoria). Advice and assistance was provided by Monica Hersburgh, Brenda Skene, Mick Keenan (Parks Victoria), Zac Walker and Zac Atkins (La Trobe University), Nick Clemann (Arthur Rylah Institute).

Report produced by: Arthur Rylah Institute for Environmental Research Department of Environment, Land, Water and Planning PO Box 137 Heidelberg, Victoria 3084 Phone (03) 9450 8600 Website: www.delwp.vic.gov.au

Citation Tolsma, A and Shannon J (2018) Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria. Arthur Rylah Institute for Environmental Research. Unpublished client report for Parks Victoria, Department of Environment, Land, Water and Planning, Heidelberg, Victoria Contents

1. Project brief ...... 1

2. Introduction ...... 1

3. Methods ...... 2 3.1 Contemporary damage – site selection...... 2 3.2 Contemporary damage – field visits ...... 2 3.3 Temporal changes in activity ...... 2 3.3.1 ARI bog sites, 2006-08 to 2017 ...... 3 3.3.2 Parks Victoria riparian sites, 2012 to 2017 ...... 3 3.4 Data analysis and reporting ...... 5

4. Results ...... 6 4.1 Contemporary damage...... 6 4.1.1 Bogong High Plains - South ...... 8 4.1.2 Bogong High Plains - North ...... 16 4.2 Temporal changes in activity and extent ...... 21 4.2.1 ARI bog sites, 2006-08 to 2017 ...... 21 4.2.2 Parks Victoria riparian sites, 2012 to 2017 ...... 22

5. Discussion ...... 25

6. References ...... 26

Appendix A Condition trend data, all surveys ...... 27

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria i Final report

1. Project brief

Feral horses pose a threat to and damage the environmental values of the Victorian alps, including areas of the Bogong High Plains. To address this threat, Parks Victoria has for some time undertaken a trapping program to reduce the number of horses, and hence the damage they have on sensitive alpine flora and fauna. Damage to alpine ecosystems by feral horses has been well-demonstrated in the past. This project aimed to visit a range of locations across the Bogong High Plains to document the nature and extent of feral horse impacts, and as far as possible, how these impacts have changed over the last decade.

2. Introduction

The environmental impacts of horses around the globe are well documented, and include damage to riparian systems, erosion, pugging, soil compaction, weed invasion, reductions in plant biomass, decreases in plant species richness and abundance, and reductions in ground-dwelling fauna (Beever and Brussard 2000; Beever et al. 2008; Giuliano and Homyack 2004; Kauffman and Krueger 1984; Loydi and Zalba 2009; Rogers 1991; Summer 1986; Zalba and Cozzani 2004). Australia’s alpine ecosystems might be especially susceptible to these negative impacts, as they did not evolve with heavy, hard-hoofed animals (Ashton and Williams 1989; Carr and Turner 1959; Green et al. 2005). Activity by horses (and other large ungulates such as deer and cattle) represents a type and intensity of impact to which alpine plants and communities are unlikely to be adapted, a fact that was recognised by the listing, in 2011, of degradation by feral horses as a threatening process under the Flora and Fauna Guarantee Act 1988 (FFG). Feral horses have occurred in the Victorian high country since the late 1800s, particularly in the far east of the state, but also on the Bogong High Plains, Victoria’s largest area of alpine treeless vegetation and part of the Alpine National Park. Concerns about the negative impacts of these feral horses on the environmental values of the alpine region were raised many decades ago (Costin 1954), and continue today (Robertson et al. 2015).

In an attempt to protect sensitive environmental values, Parks Victoria has undertaken trapping programs to reduce horse numbers. However, whilst trapping may have reduced horse numbers, remaining horses continue to damage alpine ecosystems. These negative impacts have been documented in the past through a number of assessments, including those undertaken by Arthur Rylah Institute for Environmental Research (2006 to 2008), Parks Victoria (2012) and specialist contractors assessing the condition of alpine bogs across Victoria.

To inform on-going management of feral horses in the Bogong High Plains area, there was a need for a contemporary assessment to describe both the nature and extent of impacts of feral horses on environmental values, and as far as possible, determine how these have changed over time. This project aimed to use field-based assessment of multiple sites across the Bogong High Plains to determine if there was evidence of the presence of feral horses at each site, gather evidence of damage to environmental values by feral horses at each site and describe the nature of any impacts detected. It included sites that have been assessed in previous studies, enabling documentation of any changes that have occurred over time. The broad aims were to: 1. Gather visual (including photographic) and descriptive evidence that documented the nature and geographic extent of current negative impacts of feral horses on environmental values in the Bogong High Plains area. 2. Describe any changes in the nature and extent of negative impacts of feral horses on environmental values through repeat surveys of alpine bogs first assessed around a decade ago, and riparian sites assessed as part of a separate study in 2012.

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 1 Final report 3. Methods

3.1 Contemporary damage – site selection Current impacts were determined by field inspections of areas known, or suspected, to be utilised by feral horses within the study area. This necessarily covered a range of alternative vegetation types and altitudes, as feral horses do not occupy the high-altitude plains in winter. Our understanding of where horses over- winter, and the vegetation types preferentially occupied, was limited, although we knew that they preferred access to open, grassy areas and water/riparian zones (Dawson 2010; James et al. 1999), and did not generally frequent dense forest (Walter 2002). The identification of suitable areas for searching and inspection was therefore based on expert input from colleagues familiar with the activities of horses on the Bogong High Plains, including researchers, and DELWP and Parks Victoria regional staff.

Information from colleagues informed the locations for the field work, and considered:  Where signs of feral horse activity had been seen  Where horses might occur in particular parts of the landscape, in particular seasons  Where horse activity was thought to be greatest (broad area, vegetation type, specific locations)  Where horses might over-winter  Any evidence that the intensity or extent of damage was changing

3.2 Contemporary damage – field visits Following input from colleagues, a list of suitable broad areas was drawn up for field assessment. This list covered the range of areas known to be used or deemed to be suitable for feral horses, including lower altitude areas where horses may have over-wintered. Inspections were then undertaken in a manner that maximised the number of site assessments or areas able to be covered within the time allocated, and included as many as possible of sites assessed previously (see next section). Priority areas included McNamaras Hut and Mt Jim at the southern edge of the study area, where horses had been seen for some years, and Mt Nelse and Hollonds Knob in the north-eastern part of the study area, where horses were being putatively seen for the first time in around 50 years.

Visual and photographic evidence were gathered during field inspections, including the presence and intensity/extent of:  Dung piles  Trampling and pugging  Browsing/grazing damage  Stream bank damage  Tracks  Bare ground (from roll pits etc.)  Damage to assets (such as chewed wooden signs)

Care was taken to record only those impacts obviously attributable to feral horses, as some current activity may have been attributable to deer, and some persistent bare or weedy areas may still have been the result of a long history of cattle grazing on the plains. In any event, horse hoof prints are quite distinctive, so observers had little trouble in ascertaining the agent of contemporary disturbance. Waypoints for records of obvious damage were recorded using a GPS, to enable mapping of the extent of activity, and possible future monitoring.

3.3 Temporal changes in activity Feral horses are drawn to riparian habitats, and numbers may be concentrated around watering points, particularly in times of drought. Damage from feral horses are very noticeable in these wetter areas, especially alpine bogs, because hoof prints are created easily and persist, due to the plastic flow of soft organic soils around hard hooves and the displacement of vegetation. Existing data held by the Arthur Rylah Institute (2006 to 2008) and Parks Victoria (2012) provided the opportunity to compare the extent and

2 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report intensity of contemporary activity of horses in alpine bogs and riparian zones with that detected previously (Figure 1).

3.3.1 ARI bog sites, 2006-08 to 2017 Between 2006 and 2008, 99 representative alpine bogs across the Bogong High Plains had been assessed to quantify disturbance from a range of agents, including deer, cattle and horses (Figure 1). As many of these sites as possible (56 sites) were revisited and re-assessed for horse damage, providing robust, quantitative activity data to inform whether horse damage had changed in intensity or geographic extent over the last decade or so. Priority sites were those south and west of Pretty Valley (McNamaras Hut to Mt Jim), where horse activity was most common until recently, and north of Rocky Valley Storage (Hollonds Knob to Mt Nelse and Warby Corner), where horse activity had previously not been recorded.

Using maps and existing waypoints to find the bogs, each bog was assessed for obvious feral horse activity, and an estimate made of the total proportion of the bog impacted by trampling, pugging, dung, bare ground, vegetation pulling etc. This estimate was to the nearest 1% (for <5% of bog area affected) or the nearest 5% (for ≥5% affected). As mentioned previously, care was taken to only record the impact obviously attributable to feral horses, as some activity was due to deer, and some bare areas may still have been due to a long history of cattle grazing on the plains.

3.3.2 Parks Victoria riparian sites, 2012 to 2017 Sites surveyed in 2012 (Figure 1) were part of an Australian Alps-wide assessment of horse damage in treeless streamside (riparian) areas above 1100 m elevation (Robertson et al. 2015). Twenty two of the 186 sites assessed in that research were within the focus area of the current study and were therefore directly relevant, and of these 14 were re-assessed.

Ten parameters that characterised the intensity of horse activity were estimated along 50 m sections of stream bank (Table 1). Some of these sites contained alpine bog and wet heath vegetation, others were predominantly within wet tussock grassland. Horse presence had been evident at many of these sites in 2012, but those on the northern Bogong High Plains were obviously free of horses at the time and had been treated as ‘control’ sites. The current surveys were designed to detect changes in presence/absence, and the degree of activity, since the previous surveys.

Using maps and waypoints as before, and assisted by site photos, each riparian site was re-located, then delineated using a 50 m tape to form the transect. Ten parameters (nine of them categorical) were assessed within 20 m either side of the transect line, including the number of horse tracks, the level of impact of horse tracks, the degree of ‘pugging’ and trampling damage on stream banks, the intensity of horse grazing and the number of dung piles (Table 1). This allowed direct comparison with the original variables from the 2012 data. Photographs were taken at each site from approximately the same location as previous surveys.

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 3 Final report Figure 1: Provisional study area on Bogong High Plains, Victoria. Red dots are alpine bog sites assessed between 2006 and 2008. Green dots are riparian sites assessed in 2012.

4 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report Table 1: Parameters for Parks Victoria’s riparian assessments, 2012 (Robertson et al. 2015). All assessments are within 20 m either side of a 50 m transect that follows the stream line. Qualitative scores are synthesised into an overall condition score.

Identifier Parameter Description

T4 Number of horse tracks Number of horse tracks within 20 m of drainage system, and whether they crossed the stream. Four categories. T5 Impact of horse tracks Level of impact of horse tracks, including depth, visibility and soil exposure. Four categories. T6 Stream bank impacts Characterisation of stream bank impacts such as slumping, active erosion and pugging, with respect to the steepness of the drainage line walls. Five categories. T7 Longitudinal profile of The extent to which the drainage line was being straightened or drainage line broadened by horse activity, in combination with degree of sediment movement or increased drainage. Four categories. T8 Vulnerability to erosion Vulnerability of disturbed bank materials to erosion, with respect to the nature of displaced soil material and the level of cohesion provided by fringing vegetation. Three categories. T9 Pugging Density (pug marks per m2) and depth of horse pugging on bank or channel. Four categories. T10 Grazing disturbance Extent of grazing disturbance on the banks or channel, including grazing height and vegetation pulling. Four categories. T11 Vegetation cover Percent vegetation cover along stream banks. Five categories. T12 Origin of plant cover Proportion of native versus exotic plant cover. Five categories. Dung Quantity of dung Number of discrete piles of dung within 20 m either side of transect.

3.4 Data analysis and reporting The repeat surveys aimed to gather robust temporal data to determine if horse activity was consistently changing in geographic extent or severity across the Bogong High Plains. The nature of the project meant data were treated in a descriptive manner using summary statistics and activity maps.

Parameters included:  Geographic extent of current horse activity around the Bogong High Plains, using data from all sites assessed 2017  Change in the geographic extent of activity since 2006-08 (alpine bogs) and 2012 (riparian zones), using data from repeat assessments  For southern Bogong High Plains sites, change in the intensity of horse activity in alpine bogs since 2006-08, and in riparian zones since 2012, using data from repeat assessments  General observations and photographic evidence of horse impacts from the Bogong High Plains and adjacent areas

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 5 Final report 4. Results

4.1 Contemporary damage During November and December 2017, 106 sites (70 existing and 36 new) were assessed across the Bogong High Plains to determine the extent and intensity of horse activity (Figure 2, Appendix A). Horse activity was noted at 60 of these sites (57%), including 38 of 54 on the southern part of the plains, and 22 of 52 on the northern end of the plains (north of Rocky Valley Storage). The high proportion of sites with horse activity was expected, as new assessments had targeted areas where horses were known or suspected to be present. Thus, 35 of 36 new sites showed negative impacts (Appendix 1).

The assessments indicated that feral horses were impacting on environmental values across an extensive area of the Bogong High Plains, with stream bank damage, pugging, trampling of wet areas, dung deposition, creation or widening of tracks, roll pits, pulling of vegetation and general trampling. Activity was most noticeable in grasslands (especially in areas where some shelter against the elements was provided by snowgum woodland), and around watering points, but was also common in riparian zones and on the edges of alpine bogs that are listed under both the Environment Protection and Biodiversity Conservation Act 1999 (EPBC) and Flora and Fauna Guarantee Act 1988 (FFG).

6 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report Figure 2: Sites assessed for horse impacts across the Bogong High Plains, November to December 2017. Sites with evidence of horse activity are coloured red.

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 7 Final report 4.1.1 Bogong High Plains - South Feral horses have been observed on the southern end of the Bogong High Plains for some years now, particularly in the more remote region around McNamaras Hut, Youngs Top, and Mt Jim. As expected, feral horse damage was conspicuous in this region, with the worst impacts observed around Youngs Top. Stream banks were damaged at watering points and crossings (Figures 3 & 4), reflecting a known preference by feral horses for riparian habitats (Dawson 2010; James et al. 1999). Banks had been trampled with evidence of slumping, releasing soil material into the stream, and areas of short turf had been created.

Figure 3: Stream bank damage by feral horses near McNamaras Hut. Note the bank slumping and closely-cropped turf.

Figure 4: More stream bank damage near McNamaras Hut.

8 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report The preference shown by feral horses for wet areas was also seen in extensive damage from activity in EPBC- and FFG-listed alpine bogs, especially in the Youngs Top area. Damage was sometimes in the form of simple tracks leading into or through them (Figure 5), but also consisted of more extensive damage in and around the bogs (Figures 6 to 8). Such damage has the potential to create drainage lines that channel water away from the bog and incrementally lower the water table, posing a substantial threat to the long-term hydrological integrity of affected bogs. Tracks were also well-formed in grassland and open heathland areas regularly used (Figure 9).

Figure 5: Feral horse track through EPBC-listed alpine bog near Mt Jim.

Figure 6: Degraded alpine bog hummock area in site PV13, Youngs Top. This bog is trampled over 35% of its area.

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 9 Final report Figure 7: Another view of the degraded alpine bog hummock area in site PV13, Youngs Top.

Figure 8: Trampled area at edge of alpine bog, site PV57, Youngs Top.

10 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report Figure 9: Feral horse track adjacent to stream near McNamaras Hut. This area is remote from bushwalking tracks.

Roll pits were evident in sheltered grasslands and other areas favoured for grazing and camping (Figures 10 to 16). The roll pit in Figure 10, and a shallower one nearby, were not observed when an adjacent streamside transect was assessed in 2012, indicating that damage has continued to accumulate in areas where horses are present.

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 11 Final report Figure 10: Roll pit formed since 2012 by feral horses near McNamaras Hut. A second, shallower roll pit is close by. Note again the close-cropped turf.

Figure 11: Roll pit formed by feral horses near Mt Jim.

12 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report Figure 12: A second roll pit formed by feral horses near Mt Jim, within 50 m of that in Figure 8.

Figure 13: Roll pit formed by feral horses, 2 km south of Youngs Hut.

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 13 Final report Figure 14: Damage by feral horses, 500 m from Youngs Hut.

Figure 15: Roll pit formed by feral horses, site PV55, Youngs Top.

14 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report Figure 16: Roll pit formed by feral horses, site PV56, Youngs Top

Dung deposition was common and most visible in grasslands, where feral horses had also created areas of closely-cropped turf and contributed to local domination by exotic herbs and grasses (Figure 17). Riparian zones were also impacted by dung, with 18 discrete piles of dung counted along a single 50 m long transect near McNamaras Hut.

Figure 17: Typical dung deposit near gnarled old Snowgums, Mt Jim. Note the bare ground.

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 15 Final report 4.1.2 Bogong High Plains - North Extensive feral horse activity was observed across the northern Bogong High Plains, and anecdotal evidence from alpine researchers familiar with the region suggests that this is the first time in around 50 years that such activity has been documented. Altitude appeared to be no barrier to summer horse activity, with evidence of horses at elevations as high as 1840 m at Warby Corner (north of Mt Nelse North). Negative impacts from feral horses were similar to those observed on the southern Bogong High Plains, but have occurred across an extensive area within a surprisingly short time in the presence of only a small number of horses (11 adults and 2 foals were counted 2017 by several independent observers including researchers and DELWP staff). Pugging and general trampling were most evident in grasslands and herbfields, but also seen in more sensitive areas such as carpet heath (Figure 18) and alpine bogs (Figure 19). Carpet Heath (Pentachondra pumila) is a slow-growing, mat-forming shrub found only in high-elevation areas, and is often found in areas where harsh environmental conditions retard vegetation growth. Grazing, through the action of hard hooves on organic soils, can act to maintain or increase the amount of bare ground, leaving the soil susceptible to frost heave and erosion. EPBC-listed alpine bogs are also particularly susceptible to damage by large ungulates, and even slow, incremental damage (Figure 19, but also Figures 5 to 8) can lead to track incision, lowering of the water table and eventual bog contraction. Interestingly, two foal carcasses were found in the bogs (which form the headwaters of mountain streams) in the Wild Horse Creek valley, but it is not known whether they were predated or died of natural causes (Figure 20).

Figure 18: Horse print on Carpet Heath (Pentachondra pumila). This is a slow-growing mat-forming shrub found only at higher elevations.

16 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report Figure 19: Horse print on peat and Sphagnum within alpine bog, northern Bogong High Plains.

Figure 20: Remains of one of two dead foals within alpine bog at Wild Horse Creek.

Formation or widening of tracks and deposition of dung (Figures 21 to 23) have occurred across an extensive area of the northern Bogong High Plains within a very short period of time. Dung was especially noticeable within preferentially-used grassland and open heathland, but was also seen in and around many alpine bogs.

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 17 Final report Figure 21: Dung piles formed in grassland by feral horses near Mt Nelse

Figure 22: Horse track and dung piles in grassland and open heathland near Mt Nelse.

18 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report Figure 23: Feral horse dung in EPBC-listed alpine bog at head of Watchbed Creek. Hollonds Knob is in the background.

Roll pits were already developing in grassland and open heathland within a year or so of occupation by feral horses (Figure 24 & 25), highlighting the ease with which large ungulates can damage soft alpine soils.

Figure 24: Roll pit formed by feral horses in sheltered grassland near Mt Nelse.

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 19 Final report Figure 25: Roll pit forming by feral horses near Hollonds Knob.

General trampling was observed over a large area along with pulling of vegetation (Figures 26 & 27), including pulling of Poa in grasslands, and Empodisma and Astelia in EPBC-listed alpine bogs.

Figure 26: Pulling of Empodisma minus in EPBC-listed bog at the head of Watchbed Creek.

20 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report Figure 27: Pulling of Astelia alpina by feral horses, Watchbed Creek.

4.2 Temporal changes in activity and extent

4.2.1 ARI bog sites, 2006-08 to 2017 In 2006-08, damage due to feral horses had been observed in only 4 of 99 bogs assessed across the Bogong High Plains, and these occupied sites were all on the southern end of the plains (two bogs near McNamaras Hut and two on Youngs Top). No feral horse activity had been observed on the plains north of Rocky Valley Storage. In 2017, feral horse activity was observed for the first time in 9 bogs on the northern part of the plains, including around Marm Point, Hollonds Knob, Mt Nelse and Warby Corner (Figure 28). Horse activity at an additional site appeared to be from trail horses, and is not included in this number. Despite only around 13 horses being present on the northern Bogong High Plains (section 4.1.2), activity already spanned an area of some 40 km2. This indicated a substantial expansion within a very short time of the geographic range of feral horses across the Bogong High Plains. The data also suggested that there had been an increase in the extent of feral horse activity in existing ‘horse-present’ sites, with the number of bog sites affected on the southern end of the plains increasing from 4 bogs to 9 bogs (Figure 28, Appendix A). Two riparian sites showed a decrease in condition score on the northern Bogong High Plains despite horse presence not being recorded (Appendix A). These sites exhibited increased stream bank disturbance from ungulates, but hoof prints were indistinct. This increase in observable impact is consistent with literature on feral horse activity, which suggests that damage is cumulative, that is, with even a small number of animals, the rate of damage is greater than the rate of natural repair (Greenwood and McKenzie 2001). Overall, 7 of 23 bogs previously assessed on the southern end of the Bogong High Plains experienced an increase in the intensity of feral horse activity, that is, they were in a worse state based on the estimated percent of bog area impacted (Figure 29 and Appendix A). Fourteen bogs on the southern Bogong High Plains were deemed to be in the same state as before. o Over the period 2006 – 2008, less than 4% of bogs assessed on the Bogong High Plains showed evidence of feral horse impacts. By 2017, this has increased to approximately 32%.

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 21 Final report o Previously, feral horse activity had not been recorded in assessments north of the Rocky Valley Storage, but during the recent assessment, more than a quarter of the sites assessed in this area are now affected by horses. o Not only did the proportion of impacted sites increase, so too did the intensity of impacts, with approximately 30% of mossbeds and 35% of stream areas assessed showing greater signs of damage in 2017 than in previous assessments.

4.2.2 Parks Victoria riparian sites, 2012 to 2017 The re-assessment of 14 riparian sites (which included a mix of bogs and stream banks) supported, to a small extent, the range expansion indicated by the alpine bog data, with one site on the northern Bogong High Plains, deemed to be a horse-free ‘control’ site in 2012, now showing clear evidence of horse activity, with stream bank damage, tracks, pugging and dung (Figure 28 and Appendix A). Other existing riparian sites in this northern area have not yet been obviously damaged by horses, although horse negative impacts by horses were evident in adjacent grasslands and open heathlands. Two riparian sites showed a decrease in condition score on the northern Bogong High Plains despite no clear evidence of horse presence along the transects (Appendix A). In these instances, the disturbance to the stream banks was simply too difficult to ascribe to a specific agent, although, again, damage due to horses were evident in adjacent vegetation. An increase in the intensity of activity was also noted in riparian zones previously assessed on the southern Bogong High Plains, where horses have been present for many years. Seven riparian sites were re- assessed in that region, and a worsening in state, based on reductions in condition score, were found in four of them (Figure 29 and Appendix A). For example, dung increased from 3 piles to 18 piles along the transect in the McNamaras Hut site (PV08), and the extent of stream damage increased. Further, two roll pits observed 2017 in grassland adjacent to that site had not been there when it was assessed in 2012. The largest drops in condition score were seen in sites in the remote Youngs Top area. For example, site PV13 (see Figures 6 & 7) was now trampled over an estimated 35% of its area. Three riparian sites re-assessed on the southern Bogong High Plains were in the same state as before (Figure 29), but no sites in that region experienced an improvement in condition score. Despite a relatively small number of horses being present, soil and vegetation condition has measurably declined in many sites for which previous survey data were available, supporting the concept of cumulative damage. There is unlikely to be a minimum population size for feral horses that would not lead to incremental, on-going degradation.

22 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report Figure 28: Changes in the geographic extent of feral horses on the Bogong High Plains between 2006-08 (bogs, triangles) or 2012 (riparian sites, circles) and 2017, based on the presence of horse activity. Red symbols represent sites where horse activity had not been previously recorded.

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 23 Final report Figure 29: Change in condition state of sites re-assessed on the southern Bogong High Plains. Changes in bog sites (triangles) are based on the % area impacted. Changes in riparian sites (circles) are based on streambank condition score.

24 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report 5. Discussion

Feral horses are impacting on the environmental values of the Bogong High Plains, with stream bank damage, pugging, trampling of alpine bogs, dung deposition, widening or formation of tracks, creation of roll pits, creation of short-grazed turf, pulling of vegetation and general trampling. Activity is most visible in grasslands and open heathlands (especially in frequently-occupied areas or ‘camps’ where some shelter against the elements is provided by surrounding snowgum woodland), but is also common on the edges of EPBC- and FFG-listed alpine bogs and along riparian (streamside) zones. The greatest damage was seen around Youngs Top, a relatively remote area where feral horses have been active for some time.

The geographic range of feral horses on the Bogong High Plains has expanded substantially since surveys were previously undertaken in 2006-08 and 2012, and most of this expansion has occurred in the last year or so. Activity was recorded 2017 at many existing alpine bog and riparian sites on the northern Bogong High Plains (north of Rocky Valley Storage) that had previously been completely horse-free. Altitude was no barrier to summer use by feral horses in this region, with negative impacts observed on the highest-elevation areas of the plains around Mt Nelse North.

The effect of feral horses on the northern Bogong High Plains has been swift. Within 10 years, with only a small mob of around 13 horses present, tracks have developed or expanded, roll pits have been created, grasslands have become noticeably grazed and trampled, and dung has been scattered across an area some 40 km2. The amount of dung across the plains is expected to increase several-fold over the coming years if horse numbers remain at the current level, because dung takes around five years to decompose under alpine conditions (Meagher 2004). The severity and extent of damage has also increased on the southern Bogong High Plains where horses were previously present, with negative impacts observed at more sites, more stream bank damage and piles of dung observed along streamside transects, and higher proportions of bog area affected.

The findings of this research support the claims in the scientific literature that damage caused by heavy grazing animals is cumulative over time. For example, pastures that are lightly grazed will eventually reach the same compacted state as pastures that are heavily grazed (Greenwood and McKenzie 2001). There is unlikely to be an acceptable, minimum population size that would avoid incremental, on-going degradation. Adverse impacts on soil, vegetation, fauna habitat and catchment condition, with even a small number of feral horses, will continue to increase, compromising the environmental values of what is Victoria’s largest, and arguably most important, alpine treeless region.

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 25 Final report 6. References

Ashton D. H. & Williams R. J. (1989) Dynamics of the sub-alpine vegetation in the Victorian region. In: The Scientific Significance of the Australian Alps: The Proceedings of the First Fenner Conference on the Environment (ed R. Good) pp. 143-68. Australian Alps National Parks Liaison Committee. Beever E. A. & Brussard P. F. (2000) Examining ecological consequences of feral horse grazing using exclosures. Western North American Naturalist 60, 236-54. Beever E. A., Tausch R. J. & Thogmartin W. E. (2008) Multi-scale responses of vegetation to removal of horse grazing from Great Basin (USA) mountain ranges. Plant Ecology 196, 163-84. Carr S. G. M. & Turner J. S. (1959) The ecology of the Bogong High Plains I. The environmental factors and the grassland communities. Australian Journal of Botany 7, 12-33. Costin A. B. (1954) A Study of the Ecosystems of the Monaro Region of New South Wales. Soil Conservation Service, NSW, Sydney. Dawson M. (2010) Draft Literature Review of Feral Horse Impacts - Barmah Forest. Unpublished report to Parks Victoria. Giuliano W. M. & Homyack J. D. (2004) Short-term grazing exclusion effects on riparian small mammal communities. Journal of Range Management 57, 346-50. Green K., Good R. B., Johnston S. W. & Simpson L. A. (2005) Alpine grazing in the Snowy Mountains of Australia: degradation and stabilization of the ecosystem. In: Land Use Changes and Mountain Biodiversity (eds E. Spehn, M. Liberman and C. Korner). CRC Press LLC, Boca Raton, FL. Greenwood K. L. & McKenzie B. M. (2001) Grazing effects on soil physical properties and the consequences for pastures: a review. Australian Journal of Experimental Agriculture 41, 1231-50. James C. D., Landsberg J. & Morton S. R. (1999) Provision of watering points in the Australian arid zone: a review of effects on biota. Journal of Arid Environments 41, 87-121. Kauffman J. B. & Krueger W. C. (1984) Livestock impacts on riparian ecosystems and streamside management implications...a review. Journal of Range Management 37, 430-8. Loydi A. & Zalba S. M. (2009) Feral horses dung piles as potential invasion windows for alien plant species in natural grasslands. Plant Ecology 201, 471-80. Meagher D. (2004) A count of cattle droppings in Pretty Valley, Bogong High Plains. Unpublished report to the Alpine Grazing Taskforce. Robertson G., Wright J., Brown D., Yuen K. & Tongway D. (2015) An Assessment of Feral Horse Impacts on Treeless Drainage Lines in the Australian Alps. Australian Alps Liaison Committee. Rogers G. M. (1991) Kaimanawa feral horses and their environmental impacts. New Zealand Journal of Ecology 15, 49-64. Summer R. (1986) Geomorphic impacts of horse traffic on montane landforms. Journal of Soil and Water Conservation 41, 126-8. Walter M. (2002) The Population Ecology of Wild Horses in the Australian Alps. University of Canberra. Zalba S. M. & Cozzani N. C. (2004) The impact of feral horses on grassland bird communities in Argentina. Animal Conservation 7, 35-44.

26 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report Appendix A Condition trend data, all surveys

KEY TO COLOURS Site Southern Bogong High Plains, horses previously present Site Northern Bogong High Plains, horses previously absent

Worse Impacts over greater area (bog surveys) or condition score lower (riparian surveys) Same Impacts over same area (bog surveys) or condition score same (riparian surveys) Better Impacts over smaller area (bog surveys) or condition score higher (riparian surveys) n/a: New surveys with no previous data North or Site South New or Northin Date Horses Change ID BHP Survey type existing Easting g assessed active? in state AT05 North Bog Existing 529780 5924450 30.11.17 Yes Worse AT09 North Bog Existing 530830 5920640 29.11.17 Yes Worse AT13 North Bog Existing 529960 5921440 30.11.17 Yes Worse AT15 North Bog Existing 531110 5920800 29.11.17 Yes Worse AT18 North Bog Existing 529898 5924228 30.11.17 Yes Worse AT31 North Bog Existing 530520 5920340 29.11.17 Yes Worse AT34 North Bog Existing 534970 5918560 4.12.17 No? Worse AT35 North Bog Existing 535190 5919250 4.12.17 Yes Worse AT40 North Bog Existing 529990 5921080 30.11.17 Yes Worse AT56 North Bog Existing 530730 5920150 29.11.17 Yes Worse PV16 North Riparian/bog Existing 528151 5919844 29.11.17 No? Worse PV18 North Riparian/bog Existing 531278 5921100 29.11.17 Yes Worse PV19 North Riparian/bog Existing 533267 5921115 4.12.17 No? Worse AT37 South Bog Existing 521640 5909533 18.12.17 Yes Worse AT76 South Bog Existing 523100 5913340 6.12.17 Yes Worse AT78 South Bog Existing 527600 5906790 28.11.17 Yes Worse AT84 South Bog Existing 531100 5906330 28.11.17 Yes Worse AT87 South Bog Existing 528333 5906000 28.11.17 Yes Worse AT89 South Bog Existing 528000 5905880 28.11.17 Yes Worse AT98 South Bog Existing 522140 5911300 27.11.17 Yes Worse PV06 South Riparian/bog Existing 518925 5913468 5.12.17 Yes Worse PV08 South Riparian/bog Existing 528347 5905913 28.11.17 Yes Worse PV09 South Riparian/bog Existing 520017 5908115 19.12.17 Yes Worse PV13 South Riparian/bog Existing 523768 5908901 18.12.17 Yes Worse AT03 North Bog Existing 528270 5925110 30.11.17 No Same AT04 North Bog Existing 528300 5920810 7.12.17 No Same AT08 North Bog Existing 535814 5920080 4.12.17 No Same AT14 North Bog Existing 532350 5918450 4.12.17 Yes Same AT16 North Bog Existing 529580 5921620 7.12.17 No Same AT17 North Bog Existing 528550 5925190 30.11.17 No Same AT20 North Bog Existing 534090 5919920 4.12.17 No Same AT21 North Bog Existing 529600 5925410 30.11.17 No Same

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 27 Final report North or Site South New or Northin Date Horses Change ID BHP Survey type existing Easting g assessed active? in state AT22 North Bog Existing 530190 5925370 30.11.17 No Same AT23 North Bog Existing 529430 5925690 30.11.17 No Same AT25 North Bog Existing 527713 5923984 30.11.17 No Same AT27 North Bog Existing 528911 5925570 30.11.17 No Same AT28 North Bog Existing 528560 5920420 7.12.17 No Same AT30 North Bog Existing 528660 5919490 7.12.17 No Same AT33 North Bog Existing 526790 5925030 30.11.17 No Same AT36 North Bog Existing 533750 5919760 4.12.17 No Same AT39 North Bog Existing 529530 5922060 7.12.17 No Same AT44 North Bog Existing 532740 5920900 4.12.17 No Same AT47 North Bog Existing 529640 5924560 30.11.17 No Same AT48 North Bog Existing 528730 5925320 30.11.17 No Same AT49 North Bog Existing 529770 5921700 7.12.17 No Same AT53 North Bog Existing 527503 5924514 30.11.17 No Same AT59 North Bog Existing 528050 5920430 7.12.17 No Same PV14 North Riparian/bog Existing 527134 5925242 30.11.17 No Same PV15 North Riparian/bog Existing 529447 5922074 7.12.17 No Same PV17 North Riparian/bog Existing 535541 5919284 4.12.17 No Same AT57 South Bog Existing 520410 5916510 5.12.17 No Same AT66 South Bog Existing 523780 5912630 6.12.17 No Same AT72 South Bog Existing 523590 5912440 6.12.17 No Same AT74 South Bog Existing 523830 5912720 6.12.17 No Same AT77 South Bog Existing 525360 5912640 1.12.17 No Same AT79 South Bog Existing 525590 5912500 1.12.17 No Same AT80 South Bog Existing 521730 5911560 27.11.17 No Same AT81 South Bog Existing 526200 5912300 1.12.17 No Same AT85 South Bog Existing 531080 5906760 28.11.17 No Same AT90 South Bog Existing 528115 5906350 28.11.17 No Same AT91 South Bog Existing 526051 5912414 1.12.17 No Same AT94 South Bog Existing 530505 5907020 28.11.17 No Same AT95 South Bog Existing 527245 5912179 1.12.17 No Same AT97 South Bog Existing 528503 5905984 28.11.17 Yes Same PV01 South Riparian/bog Existing 524432 5916453 3.12.17 No Same PV02 South Riparian/bog Existing 529822 5911983 1.12.17 No Same PV10 South Riparian/bog Existing 520855 5912621 5.12.17 Yes Same PV22 North Riparian/bog Existing 534241 5918103 4.12.17 No Better AT96 South Bog Existing 522400 5911360 27.11.17 No Better AT99 South Bog Existing 528480 5905660 28.11.17 Yes Better PV25 North General New 527802 5924347 30.11.17 No n/a PV28 North General New 534432 5918651 4.12.17 Yes n/a PV29 North General New 535000 5919089 4.12.17 Yes n/a PV34 North General New 531700 5921050 29.11.17 Yes n/a PV35 North General New 529750 5924020 30.11.17 Yes n/a PV36 North General New 529700 5922550 30.11.17 Yes n/a

28 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria Final report North or Site South New or Northin Date Horses Change ID BHP Survey type existing Easting g assessed active? in state PV37 North General New 534850 5918850 4.12.17 Yes n/a PV38 North General New 535700 5920300 4.12.17 Yes n/a PV39 North General New 533600 5920400 4.12.17 Yes n/a PV40 North General New 532593 5920850 4.12.17 Yes n/a PV41 North General New 532409 5919973 4.12.17 Yes n/a PV42 North General New 532400 5918750 4.12.17 Yes n/a PV23 South General New 521350 5911400 27.11.17 Yes n/a PV24 South General New 521400 5911600 27.11.17 Yes n/a PV26 South General New 524080 5916617 3.12.17 Yes n/a PV27 South General New 525000 5915700 3.12.17 Yes n/a PV30 South General New 517998 5915784 5.12.17 Yes n/a PV31 South General New 518733 5914039 5.12.17 Yes n/a PV32 South General New 518990 5912196 5.12.17 Yes n/a PV33 South General New 518976 5911838 5.12.17 Yes n/a PV42 South General New 519450 5913700 18.12.17 Yes n/a PV43 South General New 519399 5910097 18.12.17 Yes n/a PV44 South General New 519870 5909748 18.12.17 Yes n/a PV45 South General New 519588 5909183 18.12.17 Yes n/a PV46 South General New 519748 5908884 18.12.17 Yes n/a PV47 South General New 520468 5909181 18.12.17 Yes n/a PV48 South General New 520968 5909688 18.12.17 Yes n/a PV49 South General New 522766 5908893 18.12.17 Yes n/a PV50 South General New 522032 5909166 19.12.17 Yes n/a PV51 South General New 523260 5908562 19.12.17 Yes n/a PV52 South General New 522525 5908241 19.12.17 Yes n/a PV53 South General New 521838 5908116 19.12.17 Yes n/a PV54 South General New 521280 5908331 19.12.17 Yes n/a PV55 South General New 521011 5908460 19.12.17 Yes n/a PV56 South General New 521017 5908268 19.12.17 Yes n/a PV57 South General New 520602 5908276 19.12.17 Yes n/a

Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria 29 Final report delwp.vic.gov.au

30 Assessing the Impacts of Feral Horses on the Bogong High Plains, Victoria report