Control of feral horses and other Equidae
Ratification Date: 20 Jul 2023
- Feral horses have the capacity to negatively impact the environment, the welfare and sustainability of wildlife, the economy, and social amenity.
- Control programs to manage feral horses must be based on scientific assessment, and aim to minimise the welfare impact on target animals.
- Control programs must employ the most humane and effective methods applicable under Australian conditions that will achieve the objectives of the program.
- Management techniques that have higher levels of public acceptance, but poor animal welfare outcomes, should not be chosen over less popular but more humane techniques.
- Animal welfare should not be compromised by economic factors in the choice of control program
- The AVA supports adoption of strategic feral horse management plans by National and State Park authorities.
Impacts of feral horses
Feral horses were introduced to the Australian environment in the 19th Century; they are present in many parts of Australia with varying environmental, economic, social, amenity and cultural implications. They inhabit a range of land types including deserts, semi-desert plains, rocky ranges, tropical savannah grasslands, forests, scrubs, subalpine mountains, small offshore islands and even some wetlands.1 They live in small social units, either in harems, which consists of a dominant stallion, his mares and their offspring, or in bachelor groups comprised of, one to three males comprising mainly two- to four-year-olds.
A meta-analysis2 of the global impacts of feral horses on ecosystem structure, function and composition using data from 78 studies across five continents showed feral horse activity reduced environmental quality by 13% overall, with increased declines associated with increased feral horse activity. Feral horse activity had negative effects on soil, increasing erosion (by 31% on average) and reducing plant biomass and litter cover (by 25% and 31% on average respectively).
Feral horses have been found to damage waterways, cause soil degradation, negatively alter vegetation1 and impact negatively on native fauna.3
As an example, in Victoria, research suggests that feral horses are associated with vegetation types and characteristics that negatively influence the presence or abundance of Alpine Water Skink and Broad-toothed Rat4 and has shown that horse grazing and trampling reduce breeding-habitat quality for the critically endangered northern corroboree frog, Pseudophryne pengilleyi.5
Another example of negative impact is the Barmah Forest Ramsar Site. The vegetation of Barmah Forest is predominantly river red gum (Eucalyptus camaldulensis) forest and woodland (Red Gum wetland), and is part of the largest stand of river red gum in the world. The forest features a variety of permanent and temporary wetlands, including lakes, swamps, lagoons and flooded forest. The site also includes some of the most extensive stands of aquatic grasslands in the bioregion, dominated by Moira grass. The extent of Moira grass at Barmah Forest has been in constant decline since the Ramsar Site was listed in 1982. Grazing and trampling pressure by feral horses is a major contributor to this decline in Moira grass.6
Economic impacts of feral horses include competition with livestock for food and water, particularly during drought, damage to watering points and infrastructure, disruption to property management practices, and as potential vectors or reservoirs of parasites and disease (for example, cattle tick, equine influenza).1
Potential damage caused by trampling of Aboriginal archaeological sites, especially stone artefact scatters and bora grounds (earth rings) in Kosciusko National Park has been identified as an area of concern.7 In Carnarvon National Park, Queensland, feral horse damage has been done to Indigenous cultural heritage sites by horses raising dust and licking and eating the artwork. 1
Each year in Australia many thousands of collisions occur between motor vehicles and animals, (including feral horses) with around 5% of on-road human fatalities a result of hitting animals.8 Feral horses have been implicated in at least two fatalities in Queensland.9
Effective Control Techniques
Reduction or removal of a population of feral horses requires an assessment of population size and of any potential for migration from other adjacent areas. Fecundity, which is the number of females born per adult female per year across the population, provides an indication of how a population will expand. If food isn’t limited, fecundity is usually around 0.4 in most published studies3 (on average, each adult mare has 4 foals over 10 years). With adequate nutrition, a population of feral horses can be expected to double in size in approximately 11 years10 and conversely, to maintain stable numbers around 10% of the population needs to be removed annually. Theoretically, an annual reduction of approximately 50% of the population would need to be maintained for around 10 years to effectively remove a population.11
Experience gained from horse removal in Australia indicates that feral horses are slow to recolonise new areas if entire harems are removed because adjoining groups of horses seem to prefer to remain in familiar areas.10
Available control techniques include trapping and mustering followed by either shooting or removal, aerial shooting, ground shooting and exclusion fencing
Fertility control is not a currently practicable option as hormones to control fertility need to be given annually by injection; hence application is not currently feasible for most Australian conditions where feral horse numbers are high.12 Zabek (2015) cites five studies that confirm that fertility control is only feasible in small, contained and accessible populations, where every individual horse can be identified.10
Some Australians value feral horses for historical, emotive, or heritage reasons and actively resist any attempts at control. Management efforts across Australia vary significantly due to the relative abundance of feral horses, the differing pest status classifications across the states and territories, available resources, differing environments or topography, and varying existence of regional (cross-jurisdictional) management plans.
Community perceptions of control methodologies also vary and are often affected by cultural perceptions and experiences. A preference for trapping, training and rehoming horses is prevalent in some communities, however may result in poorer animal welfare outcomes than the less popular methods of ground or aerial shooting.
Feral horse control is necessary and supported, provided it is humane and justified. Every situation should be considered on its merits and should involve stakeholder consultation, expert assessment, and sound scientific understanding of the impacts of feral horses in the particular environment.
Lethal and non-lethal control programs should be well planned, resourced and coordinated, utilising personnel who are trained and accredited in the chosen control techniques.
A model for assessing the relative humaneness of pest animal control methods12 has been developed to enable the evaluation of methods in use, and to select the most humane methods based on scientific evidence.
The model examines both: the negative impacts of a control method on an animal’s welfare; and the duration of this impact (Part A); and, if a lethal method is employed, the intensity and duration of suffering of the killing technique. The information used to develop the matrix for feral horse control techniques is provided at:
According to this model, ground shooting is the most humane method of control, followed by aerial shooting, then mustering and trapping. The humaneness of mustering or trapping is highly dependent on how it is conducted; for example, retaining social groups while mustering increases welfare outcomes. The cumulative effect of all the subsequent stages (i.e. holding in the yards, drafting, shooting or transport) and how they are conducted will compound the welfare impact.
The Model code of practice for the humane control of feral horses12 has been developed to provide information and guidance to vertebrate pest managers about control programs to reduce the negative impacts of feral horses using the most humane, target specific, cost effective and efficacious techniques available. Standard operating procedures for each control method and worksheets to assess the merits of available options are available on the PestSmart website (https://pestsmart.org.au/).
Australian Animal Welfare Standards and Guidelines and Model Codes of Practice also provide guidance and the standards may be a legislative requirement in certain jurisdictions.
These include but are not limited to:
- Australian Animal Welfare Standards and Guidelines - Land Transport of Livestock: animalwelfarestandards.net.au/land-transport/ (2012)
- Model Code of Practice for the Welfare of Animals: Feral Livestock Animals (1992)
- Model Code of Practice for the Welfare of Animals: Livestock at Slaughtering Establishments. (2001)
This policy provides guidance to the government and the community about the humane management of feral horses.
Other relevant AVA policies and position statements
- Control of native and introduced animals causing damage to agriculture or habitat (2018)
- Considering welfare of target and non-target animals in planning vertebrate control programs (2019)
- Australian animal welfare standards and guidelines (2017)
- Csurhes, S, Paroz, G & Markula, A, 2016, Pest animal risk assessment, Feral horse, Equus caballus, Biosecurity Queensland, Brisbane
- David J. Eldridge, Jingyi Ding, Samantha K. Travers, Feral horse activity reduces environmental quality in ecosystems globally, Biological Conservation, Volume 241,2020,108367,ISSN 0006-3207,https://doi.org/10.1016/j.biocon.2019.108367. (https://www.sciencedirect.com/science/article/pii/S0006320719311978)
- Don A. Driscoll, Graeme L. Worboys, Hugh Allan, Sam C. Banks, Nicholas J. Beeton, Rebecca C. Cherubin, Tim S. Doherty, C. Max Finlayson, Ken Green, Renée Hartley, Geoffrey Hope et al. Impacts of feral horses in the Australian Alps and evidence-based solutions. 30 January 2019. https://doi.org/10.1111/emr.12357
- Cherubin, Rebecca C, Venn, Susanna E, Driscoll, Don A, Doherty, Timothy S and Ritchie, Euan G 2019, Feral horse impacts on threatened plants and animals in sub‐alpine and montane environments in Victoria, Australia, Ecological management and restoration, vol. 20, no. 1, Special issue: feral horses in the Australian Alps, pp. 47-56, doi: 10.1111/emr.12352.
- C. N. Foster A*and B. C. Scheele. Feral-horse impacts on corroboree frog habitat in the Australian Alps. Wildlife Research 46(2) 184-190 https://doi.org/10.1071/WR18093: 6 March 2019
- Protection of Floodplain Marshes. Barmah National Park and Barmah Forest Ramsar Site. Strategic Action Plan 2020-2023. Parks Victoria
- ‘Donaldson S & Feary S 2021 Aboriginal cultural values report: investigating Aboriginal people’s associations with wild horses in Kosciuszko National Park, NSW. Unpublished report to the NPWS’.
- Rowden, Peter J. and Steinhardt, Dale A. and Sheehan, Mary C. (2008) Road crashes involving animals in Australia. Accident Analysis and Prevention 40(6):pp. 1865-1871.
- Magdalena A. Zabek. Understanding population dynamics of feral horses in the Tuan and Toolara State Forest for successful long-term population management, 2015.
- Jim Hone,Richard P. Duncan,David M. Forsyth. Estimates of maximum annual population growth rates (rm) of mammals and their application in wildlife management, 2010: https://doi.org/10.1111/j.1365-2664.2010.01812.x
- Trudy Sharp and Glen Saunders, 2012. Model code of practice for the humane control feral horses. Standard Operating Procedure. PestSmart website. https://pestsmart.org.au/toolkit-resource/code-of-practice-feral-horsesaccessed 12-11-2022
Date of first ratification by AVA Board July 2013
Updated and re-ratified 20 July 2023