What are the risks to wildlife associated with barrier and cluster fencing?

Exclusion fencing has been used in various contexts in Australia to prevent predation and environmental damage by pest animal species for over a century. Predation by wild dogs and dingoes has a devastating impact on sheep and cattle, particularly young animals who suffer significantly from being chased and mauled. Many animals are not killed outright having to endure a slow painful death. Management of wild dogs is necessary to prevent this and exclusion fencing is considered to be one effective method to prevent predation. There are benefits from exclusion fencing, including welfare gains through reduced maiming and killing from predation of animals within a fenced area. However, there are also animal welfare impacts on animals on the outside of the fence. These can include injury, distress and prolonged death through starvation, thirst, or exposure. Furthermore, exclusion fences can halt natural wildlife movement patterns and reduce genetic interchange between populations separated by the fence, affecting biodiversity and leading to other ecological impacts [1]. The impacts of exclusion fencing is a complex issue, requiring all stakeholders to work collaboratively to overcome the many challenges presented.

Types of exclusion fences

Barrier fences

The first major barrier fence was erected in the early 1890s stretching from southern Queensland, passing through New South Wales to end in South Australia to stop dingoes from attacking sheep flocks. In the early 1900s, a state barrier fence was erected to prevent rabbits from causing environmental damage in the southern agricultural area of Western Australia. After some changes, the current fence covers nearly 1200 km and has been upgraded to exclude emus, wild dogs and kangaroos.

Cluster or cell fences

An emerging agricultural trend involves collaborative efforts by private landholders and governments to erect exclusion fences around a number of properties primarily to prevent wild dog and dingo attacks on livestock, although some nature reserves may also be included. These are known as ‘cluster fences’. In remote areas, these fences can extend for up to 300 kilometres and enclose over a hundred thousand hectares. Recent proposals in Western Australia would comprise approximately 1400km of fencing enclosing more than 7.5 million hectares. In Queensland, where cluster fencing is quite popular, fences are generally up to 1.5m high, usually comprising 8 horizontal strands of plain wire which are crossed by vertical wires 30 cm apart, and may have 1-2 strands of barbed wire on top.

Exclusion fencing is one approach used as part of an integrated pest management program where other control methods such as shooting, trapping and baiting are carried out in buffer zones adjacent to the fence. Any dingo or dog within the fenced area will be killed with some landholders also targeting predators in a ‘buffer zone’ in close proximity to the fence.

Sanctuary fences

Exclusion fencing has also been used to reduce the impact of predation on endangered native species. Purpose-built fencing, which ranges from excluding a few hundred to several thousand hectares, has been effective in establishing mainland ‘island’ sanctuaries to exclude introduced species, such as foxes and feral cats. These fences can be designed to prevent entrapment and usually cover a much shorter linear distance than cluster fencing, thus allowing animals to circumnavigate the fence. However, injuries may occur if animals flee from threats and are unable to avoid the fence.

Animal welfare risks

Where exclusion fences extend for hundreds of kilometres significant welfare risks may arise, especially for some native species. While most animals encountering a fence will move along or away from it, some will attempt to go underneath, over the top or push through it. This may result in entrapment. Animals are more likely to injure themselves if they are being chased, are desperately seeking food and water or trying to escape a wildfire. Entrapped or severely injured animals may suffer predation or a prolonged death. Animals prone to entrapment include emus and kangaroos but smaller animals are also at risk including wallabies, echidnas and goannas. In Western Australia, there have been many incidents where thousands of emus have amassed along the barrier fence, only to be shot, poisoned or perish from starvation and thirst [1]. It is predicted that these major emu movements will occur every 15 years [2]. Suffering of animals entrapped by fences is rarely alleviated, due to remoteness and limited surveillance to enable rapid intervention. Barbed wire can also inflict painful wounds, further compromising animal welfare.

Where cluster fences are erected to prevent dingo and wild dog access, kangaroo numbers may increase on the ‘inside’ of the fence due to a lack of predator pressure. These kangaroos are no longer able to disperse and may be killed if they consume or damage crops and pasture.

In other situations where cluster fencing is used and access to water is restricted, trapped wildlife will die from thirst and dehydration, unless they are humanely killed.

Conclusion

The RSPCA recognises that wild dogs and dingoes cause significant welfare impacts on farm animals and steps need to be taken to mitigate this impact. However, there is a need for greater consideration of the risks and welfare impacts of exclusion fences, and for industry and government to implement strategies to avoid animal suffering caused by these fences. Appropriate action includes undertaking regular inspections of fences, installing remote monitoring systems at known ‘hotspots’ for wildlife incidents, selecting appropriate mesh size to allow small wildlife to pass/escape, avoiding use of barbed wire, ensuring water is available for entrapped animals and using other means of protecting livestock from predation. Further research is required to mitigate welfare risks associated with exclusion fencing or to develop alternative and more humane methods of controlling wild dogs to reduce reliance on exclusion fencing.