Using Exclusion Fencing to Manage Feral Deer Impacts in Australia

Author

David M Forsyth

Centre for Invasive Species Solutions

Summary

Exclusion fencing is widely used in Australia to manage the undesirable impacts of medium-sized to large-sized mammals, including wild dogs, feral pigs and macropods. The method has high social acceptability. Fencing has been widely used to manage the impacts of deer overseas, and there is a demand from private and public land managers for information about how to use this method in Australia. This document summarises the key issues around using fencing to manage feral deer impacts in Australia.

Evidence-based fencing standards for deer have been developed as a result of the long history of farming deer in Australia and New Zealand. To exclude deer, fences should be a minimum of 1.9 m in height, have a mesh netting of 17/190/15, and posts spaced at a maximum of 10 m are recommended. Macropods, feral pigs, and wild dogs are also prevented from jumping over or pushing through fencing to these specifications. To prevent animals from pushing or digging under fencing and creating holes for deer to move through, a 30 cm netting apron is also desirable. If an apron is used, the pole spacing needs to be shorter (typically at 5 m intervals). An electric outrigger wire outside the fence (20–60 cm above the ground, depending on the mix of species to be excluded) can reduce the pressure on the fence and apron from deer, feral pigs, macropods and wild dogs.

The key issues around using deer-exclusion fences relate to whether they are being constructed in agricultural or conservation settings. In agricultural settings, it is usually desirable for the fence to also exclude macropods, feral pigs and wild dogs (if they are present), and fences are typically constructed along boundaries or around high-value paddocks; existing sheep/cattle fences can be modified to exclude deer, and new fence lines are usually cleared and levelled with heavy machinery. In conservation settings, fences typically enclose smaller areas and are more remote, and it is often not desirable or practical to clear and grade the fence lines with heavy machinery. Deer exclusion fences in conservation settings can be designed to facilitate the movement of native mammals by having a gap at the bottom of the fence, although this increases the risk of small deer getting through.

The key strategic design considerations when constructing a deer exclusion fence are whether the fence needs to keep all deer out, and how easy it will be to inspect, maintain and repair the fence. Well-constructed fences are expensive but should last more than 15 years with minimal maintenance. Regular inspection for holes and breaks is needed if there are trees within falling distance of the fence, and as soon as possible after floods.

The cost of constructing a deer exclusion fence depends on the design of the fence, the topography, and the difficulty of clearing the fence line (including any need to remove trees). An indicative total cost for using heavy machinery to clear and grade a fence line on an agricultural property, and constructing a fence that will exclude deer, macropods, feral pigs and wild dogs (i.e. including an apron) is $16,000 per kilometre. Constructing fences in remote forested or alpine areas costs much more than this per kilometre.

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