The problem of feral horses damaging grazing land, creeks, dams and waterholes as well as eating endangered native plants in wildlife habitats is being addressed by research into methods of repelling them. With culling by aerial shooting banned in Queensland and NSW, the feral horse problem is likely to get worse with the loss of feed due to the drought. Other than humans, brumbies have no natural predators as they are an invasive introduced species.
“¨”Management of feral horses is an increasing problem for property owners and protected area management alike,” University of Queensland PhD student, Sarah Joseph said. “¨Joseph, who has just submitted her PhD thesis on equine behaviour and feral horse management, has tested a range of potential repellents for small scale exclusion of feral horses from refuge habitats for native wildlife.
Using the UQ’s stable of horses, Joseph carried out four experiments on12 young, unbroken domesticated horses in open-field tests with a range of 23 possible non-violent repellants. She measured behavioural indicators of stress in an attempt to identify the most humane method of control.
“¨Changes in heart rate and behaviours such as vocalisation, defecation rate, and gait were used as benchmarks to measure the stress levels of horses in the field. Some of the stimuli were normal or non-threatening events to act as a control in the experiments.
While Joseph said time and funding restrictions meant most of her experiments were done using the UQ’s own horses rather than in the bush, she said the results were applicable to brumbies in the bush. “The literature shows that equine behavior has changed very little with the process of domestication, and my own experience with my own brumby supports that as well. I did observe a trapping and shooting operation, and I also used three brumby foals from that operation for a small experiment on brumbies versus domestics.”
An avid horseback rider since childhood, she came to Australia from California to study three years ago. “¨”I hadn’t planned on studying horses for my PhD, but this project allowed me to combine several of my passions, which was ideal.
PhD student Sarah Joseph and her brumby Mystery.
“The research aims to gain a better understanding of the underlying mechanisms of fear and repellency in horses,” she said. “¨”¨”It tests the theory that fear-provoking stimuli are more effective repellents, and I developed a novel screening method to compare repellents without undertaking costly field trials, simply using the heart rate monitors and behavioural cues.”
In deciding what stimuli to expose the horses to, “I used things that were predator-related that I was curious about, things that were recommended by other people, and things that were commercially available in herbivore repellents. With the predators, I wanted to have some from dogs/dingoes, which native wildlife have been exposed to, as well as some from big cats, which native wildlife hasn’t been exposed to.
The 23 stimuli were divided into the categories of sounds, sights and smell. Sounds included big cats, distressed horses, rabbit fear scream, ‘happy’ or contented horses, train noises, a stock whip cracking and wild dogs. Blood & bone, butyric acid, dingo faeces, dingo urine, stallion faeces and tiger faeces were included in the smells, as well as commercial herbivore repellents.
Among the visual stimuli were an aggressive stallion silhouette, lioness face (with eye spots). dingo silhouette, mare and foal silhouette and an umbrella opening.
Joseph found that sound stimuli consistently caused the strongest reaction, followed by visual stimuli, with smells being the least repellent. “This is especially interesting in light of the fact that most commercially available herbivore repellents are either smell or taste-based,” she said.
Scaring them off
The four most effective sounds were the whip cracking and the rabbit screaming horn followed by the wild dogs and distressed horse noises. In the second experiment using just these sounds, all four noises kept all the horses away for the 30 minute duration of the trial. “So it was hard to pick which was best in terms of repellency. However, the rabbit scream seemed to change the behavior of the horses (cause the most fear) overall.”
The brumby foals and the ones in the management operation were on a property in south-east Queensland, but Joseph said there would be few behavioural differences between different populations. “In my experience, a brumby is pretty much a brumby, though of course environmental conditions will vary.” She pointed out however, that, particularly during drought, “high motivation to enter an area or consume a food source may greatly reduce the effectiveness of repellents.”
Joseph hopes her research results will pave the way for future deterrence systems and techniques. “¨”¨”My general research goal is to improve wildlife conservation through a better understanding of animal behaviour,” she said.
How can land-owners put this information into practical use against feral horses? “The way I see the repellents being useful would be potentially protecting small patches of habitat from brumbies for short periods of time, (maybe a week or two on their own), but repellency could probably be achieved for much longer if they were used in combination with electric fences, and perhaps yards for trapping horses near water holes. Passive brumby trapping with feed, if it is done properly, causes very little stress to the horses.”
Brumbies being captured in Queensland