Wildlife Friendly Fencing

Fences are useful. They demarcate your land, and keep the cattle in. And if the goal is to regenerate a piece of land, then a fence can keep stray cattle out in order to arrest grazing. But useful as they are, fences also generally end up cutting off the land (an ecosystem) to most animals. This can have far reaching consequences.

Fence ecology (the effect of fences on life forms) is a relatively new discipline. The adverse effects of impenetrable barbed wire fences on ecology and wildlife migration have become clearer to humans only recently, and continue to be a subject of study and research.

Traditional barbed wire fences tend to restrict wildlife movement. Many animals and birds get tangled in them while trying to cross over. Bats, owls, owlets and eagles are especially susceptible as they tend to dive down while hunting and notice the wires too late. Leopard and deer fatalities are also reported, and many cases go unreported every year.

But besides individual fatalities, large scale fencing also causes habitat fragmentation and isolates animal populations which, in turn, leads to loss of genetic diversity. This could lead to local species extinction in a region in the long term. For this reason, the design and location of your fence is very important, and we should strive to design wildlife friendly fences that have minimal ecological impact.

Remember, the ideal option for accommodating wildlife is open habitat with no fence. This is especially true if your land sits close to prime wildlife habitat. If a fence makes the land off limits to many of the larger wildlife species, it will fail to shape up as a healthy ecosystem. 

If achieving resilience is the goal, all species should be able to access the land to maintain ecological balance. Where a fence becomes necessary (for safety, restricting grazing etc), less of it is better.

To maintain a balance between our requirement for a fence and that of wildlife in mind, we can design an outer wildlife friendly fence that keeps the cattle in/out, while allowing other species to cross and traverse through the landscape. More impermeable fences can be erected around residences/food forests/nurseries/veggie gardens/own cattle shelters to keep them secure. These fences will lie inside the land and will seal off smaller patches of it, instead of the whole property.

Features of a wildlife friendly fence:

1. Location: The fence should not restrict wildlife access to corridors and important habitats (wetlands, riparian zones) as well as access to water.

2. The fence should be highly visible to running and flying fauna. 

3. The highest and the lowest wires should allow wildlife species to either jump over or crawl under them without injury.

In order to fulfill these criteria, the wildlife friendly fence should comprise two types of sections: The standard section and the occasional Wildlife underpass/overpass section.

The standard section shown below will take care of one of the requirements (visibility) while keeping the goats and cows from coming in/venturing out. The other two requirements will be met with the wildlife underpass/overpass section.

The distance between poles/posts is 16.5 feet. 

It is important to use smooth, barbless wires for the bottom most and the topmost strand. A line of bright white cloth flags should be hung from the topmost wire for visibility (though this may not work for bats and nocturnal birds). 4 flags for the topmost wire and 3 for one of the middle wire for every section (16.5 feet) is recommended.

A gap of 12 inches between the top two wires is also important to prevent foot entanglement if an animal hops over the fence.

The majority of fence sections will the standard ones. 

The wildlife underpass and overpass section is a critical part of the wildlife friendly fence that would allow larger species to traverse the land. The dimensions here have been worked out keeping in mind deer and the sloth bear. It will also work for big cats, and will be visible to birds. Dimensions and wire heights can vary depending on the species whose habitats your land occupies, and the slope of the land near the boundary.

The topmost wire will have a white flagline for visibility. And a depression will be created under the wires to allow a “trench” around 36 inches wide and 24 inches deep. Alternately, the lowermost wire can be lifted and bound to the wire above (using a simple binding wire) to provide more space on the sides. Which method is ultimately deployed depends on the situation on the ground. 

Location of this section: 

The locations of the underpass-overpass section depend on your observations and understanding of sectors and flows (human, cattle and wildlife entry/exit points and movement) across a site. These sections will be placed closer to observed animal trails, streams, wetlands and forest edges (remember, we should strive to leave water sources and animal trails fence free if we can help it).

In addition, on a regular stretch of fence comprising standard sections, a wildlife underpass/overpass section should be installed roughly every 400 feet. We’d also try to place these sections at perimeter corners/vertices, since certain animals are able to better find openings/exits at corners.

Note: 1. The diagrams that you see here are for a goat and cattle fence. (If no goats are present, and you only need to keep the cows in/out, the wire heights from the ground should be 16” (smooth), 22” (barbed), 28” (barbed), 40” (smooth).)

2. The heights would be different on hilly/slopey terrain. The effective height of a fence changes if it stands on a significant slope. If the animal is standing downslope of a 40” fence, it would effectively have to jump much higher than 40 inches to hop over. Appropriate heights /openings should be provided in such cases.

Drop Down Sections for Elephants:

If elephants are present in the area, “drop down” fence sections will be needed. Elephants cannot crawl under or jump over any fence, and unless given an opening, will create one by taking down the fence.

As the name suggests, these sections of the fence can be dropped or removed when needed. Carefully placed drop down fence sections allow us to create safe corridors for the elephants to pass through our property, while reducing the likelihood of their taking down the fence elsewhere in order to get in. After the animals have moved on from the area, the fence can be brought back up to close the openings.

The drop down section (dark) is secured to the fence (light) using wire loops near the top and the base of the staffs.

The Base loop is permanently secured around the standard fence pole (light). 

To erect the drop down section (dark), it is placed base first into the base loop, with both poles parallel. 

The top loop is then flung over the two poles and is used to secure them. 

To “drop” the section, the process is reversed. [1. Remove the top loop > 2. Pull out the drop down section > 3. Welcome the elephants in]

A drop down section. Wire types (barbed/smooth) and the gaps between them are the same as other sections. This section isn’t fixed to the ground. Two constraint staffs are provided to maintain wire gaps, which would otherwise be subject to distortion when the section is moved.

Acknowledgements: The Wildlife Friendly Fence manual by Montana Fish, Wildlife and Parks was an invaluable guide as we created our iteration of such a fence. We would also like to thank wildlife experts Dr. Arun A Sha, Dr. Prakash Mardaraj and Dr. Yoganand K for their valuable inputs for fence parameters.