Wildlife friendly fencing

Why conventional fences are a problem

Every year, thousands of animals become entangled in fences across Australia, leading to severe injuries or death. Over 75 wildlife species have been identified as regular victims of entanglement on barbed wire fences including bats, sugar gliders, owls, koalas and kangaroos. 

The increasing installation of pest animal exclusion fencing, hinge joint fencing and electric fences can alter the natural passage of fauna throughout the landscape. This can lead to the isolation and potential extinction of native populations. 

It is critical to understand the negative impact of conventional fencing on our wildlife. It is our responsibility to adopt wildlife-friendly fencing practices to mitigate these effects.

Fences that cause problems for wildlife often:

• have barbed wire
• are too high or low to navigate
• have loose wires (except the bottom wire)
• have wires spaced too closely together
• are difficult for animals or birds to see
• create an impenetrable barrier.

Where wildlife entanglement occurs

Higher entanglement rates usually occur:

• along forested wildlife corridors
• in refuges such as creeklines
• areas between paddock trees
• patches of native vegetation and wetlands. 

Fences near food sources, and den or nesting trees can also be harmful, when moving between them. 

Barbed wire in areas such as open paddocks or roadways are unlikely to cause the same level of risk for wildlife.

Species most at risk

Some species are highly vulnerable to fence entanglement, and for several, barbed wire poses a recognised threat. Wildlife that are at high risk include: 

• Yellow-bellied glider (Petaurus australis)
• Mahogany glider (Petaurus gracilis)
• Spectacled flying fox (Pteropus conspicillatus)
• Grey-headed flying fox (Pteropus poliocephalis).

What is wildlife friendly fencing?

Wildlife friendly fences allow animals to jump over or crawl under them in a safe way. This reduces the risk of animals getting caught in a wire twist. 

Installation of fence crossing structures can also offer climbing species, such as koalas, the opportunity to travel across their home ranges normally.  

It is strongly recommended that fences do not have any barbed wire. If barbed wire must be used, it is best not to place it on the top two strands of the fence, as that is where most injuries to wildlife occur. The bottom line of plain wire should be slightly looser to allow for the movement of animals underneath the fence.

Why native wildlife gets caught

Many of our native wildlife, such as gliders, tend to move around to feed using the shortest possible distance between trees. This places them at greater risk when crossing between trees at the corner of paddocks.

Gliders and bats also make extensive use of single paddock trees. Barbed wire on fences between single paddock trees and patches of native vegetation are more likely to be the ones that are the greatest risk to our local native wildlife.

Entanglement usually occurs more often in nocturnal species like:

• gliders
• bats and microbats
• frogmouth owls
• wallabies
• kangaroos
• large winged birds
• koalas. 

While nocturnal species can see well at night, the wire on fences may not be obvious as they blend into the night. Animals may not see new fences, especially those installed across familiar routes. Newly built fences can take wildlife by surprise, leading to increased incidents.

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Designing wildlife friendly fences

Retrofitting existing fences

As a solution for existing fences, increasing the visibility or concealing the top barbed wire can effectively reduce wildlife injury. You can achieve this by using:

• poly pipe to conceal top barbed wire
• metal tags or reflective tags to increase visibility
• replacing the barb wire with plain wire.

Where you must use barbed wire, try to avoid using it on at least the top 2 strands.

Polypipe

As a temporary measure in some areas, barbed wire can be concealed on short sections of fence. A special tool to split and install polypipe is shown above. Poly pipe is effective in the short term for small sections of fence. However, it may be cheaper to remove and replace barbed wire with plain wire.

Increase visibility

To make existing barb wire visible for nocturnal animals you can use tags, electric tape, flagging tape or poly-pipe. 

Metal tags along the top wire (or old electric fencing) can be installed at a minimum of 30 cm intervals to ensure maximum visibility.

Plain wire

A cheap option to retro-fit is to assess areas of fauna movement, and simply replace barb with plain wire (for livestock) or sighter wire (for horses), on at least the top 2 strands and bottom strand. 

New fencing

For new fencing, you can assess the area and then decide the design, type and placement that is right for the location and for you! 

Alternatives to barbed wire where fencing adjoins fauna corridors or forested areas. 

There are many alternatives to barbed wire for new fences. 

• Stock-proof fences can also be constructed from multi-strand high-tensile plain wire.
• Electrified fences are another alternative, but they must be designed to ensure that stock control is effective and wildlife protection is considered.
• Virtual fencing is another option, depending on your cashflow.
• Customised gates, such as one-way gates, can be installed to facilitate the movement of native animals.

When constructing a new fence, the design should include:

• multi-strand high tensile plain wire (5 or 6 lines)
• avoid placing barbed wire on the top two strands if it must be used
• a loose bottom wire 30 cm above the ground
• posts at 5 m intervals
• fence height around 90 cm.

Maintaining existing trees near the fence can also help to facilitate the movement of animals.

Koala fence crossings

A canopy bridge or koala bridge placed along a fence line can provide wildlife with easy access to essential habitats and enables them to move freely across the landscape.

Additionally, a timber post or log can be leaned against an existing fence near the koalas’ natural path to support their movement.

Building a koala fence crossing over existing fencing allows koala passage through the landscape where electric fences or pest animal exclusion fences may prevent normal migration patterns.

Building a koala fence crossing

Materials required:

• Pine CCA treated logs with 125-150mm diameter
• Long bolts, washers and nuts
• Pine lengths for baffles if required
• Cement

Steps:

1. Cut the poles to length so that they extend approximately 300mm above the height of the crossbar. This is to encourage koalas to climb up and above the crossbar before reaching out to the opposite pole.
2. Ensure the crossbar is at least 400mm above the electric wire to reduce the likelihood of the tails of other animals like possums from touching the electrified wires.
3. Attach baffles between the poles and the fence to encourage koalas to climb the outside of the pole away from the electrified wires.
4. Use baffle width to position the poles as close as possible to the fence. You want the koala moving along a fence line to ‘bump’ into it and if too far from the fence it may not encounter the pole. 

While cost and other logistics will most likely determine the number and position of crossings, one should be built within each koala home range (which spans an approximate 500 metre area).

Monitoring crossing locations

Consider installing a remote camera to monitor sites prior to installing crossing structures. This may help you work out the best location to install the crossings.

A remote camera set up on the crossings once they have been installed will also help you monitor their use, and any design improvements you think may be helpful.

What to do if you see an animal trapped in a fence

If you find an animal entangled, there is still a chance to rescue it. However longer they are on the wire, the worse chance they have. For all rescues you will need to act quickly.

1. Put on some gloves and use a towel or cloth to carefully hold the animal still and keep it calm.
2. Careful covering of the animal's eyes or head (with a cloth or towel) will help calm it down.
3. You may need to cut the whole barbed section of wire, and then remove the animal from the barb carefully once in a safe location that is easier to work in.
4. If you have successfully disentangled an animal, it may be dehydrated and in shock.
5. Place the animal in a box with a breathable cover in a quiet and cool place, leave a shallow dish with water in the box. Do not force-feed animals water as you can drown them.
6. Contact a local wildlife carer/ vet immediately.