Wildlife-friendly fencing for the win
Cow elk, Riding Mountain Aspen Parkland, Manitoba (Photo by NCC)
Wire fencing is a common feature across southern Manitoba’s rural landscape. Its functional in its role to contain livestock, delineate property boundaries, and in some cases, exclude wildlife. Unfortunately, these fences may also have unintended consequences.
A growing body of evidence has shown that fences can have negative impacts on wildlife, such as mortality from entanglement in wires and impact by birds during flight, and impediments to migration and movement through landscapes. Fortunately, as the Nature Conservancy of Canada's (NCC's) Manitoba Region has learned of these impacts, we have identified and implemented solutions.
On NCC lands, we always seeks first to remove unnecessary fencing. Where fences are required, we rely on using wildlife-friendly fencing approaches and incorporate new techniques and knowledge that become available. Below are some of the techniques used to improve the wildlife friendliness of necessary fences:
Remove all page (woven) fence wherever possible. This gives juveniles and adults of some species an opportunity to crawl under or through fences.
A bottom wire or rail at least 18” (46 cm) above the ground. The higher this bottom wire, the better for wildlife. Studies have shown that when a bottom wire is raised, the crossing behaviour of ungulates changes from jumping over to crawling under. When elk are present in large numbers, a minimum of 21” (53 cm) should be used. Instead of repositioning entire strands, a quick fix can be made in a section by clipping or wiring the bottom two sections together to enable easier passage under. This is ideal in areas where frequent crossings occur, such as at wildlife trails or near watering sources, and in sections where increased ground slope effectively raises top wires.
A top wire or rail preferably no more than 40” (1.02 m) and a maximum of 42” (1.07 m) above the ground. The lower the top feature, the better for wildlife. A lower top wire is easier to jump over and decreases instances of entanglement between the top two wires. This is also ideal in areas where frequent crossings occur, near water sources, and in sections located on increased ground slopes.
Increase visibility with a top rail, pvc pipe or visibility markers. This may increase successful jump crossing because ungulates are better able to judge the necessary height. Some studies have demonstrated that animals may be initially deterred by these features but become accustomed to, and sometimes drawn toward, marked sections that have other wildlife-friendly features in place. Increasing the visibility of the top wire (and other levels) significantly decreases collisions with fences by birds. Marking wires in open landscapes like agricultural, grasslands and wetlands is of greater importance because birds are unaccustomed to vertical features in those areas. For each section of fence, a minimum of two markers should be placed on the top wire. The most cost-effective, yet durable, marking technique uses 3” (7-8 cm) pieces cut from vinyl “undersill” or trim siding strips. The undersill siding has a lip that can be snapped onto barbed wire fence, with the barbs keeping the markers from sliding.
Gates, drop-down fence sections, or other passages where wildlife concentrate and cross. Landowners and managers will be familiar with the lands they manage to know where areas of frequent fence repairs, entanglement or crossing occur. In those areas, a solution includes leaving gates open when possible, or creating droppable sections when livestock are not present. If those features are not possible, several of the other wildlife-friendly features can be incorporated.
At least 12” (30 cm) between the top two wires. Though yet to be documented, it remains intuitive that having a larger gap between the top and second wires would decrease probability of entanglement when fences are jumped over.
Smooth wire or rail for the top, smooth wire on bottom. Animals that are scratched and have hair removed while passing over or under fences may have reduced survivorship.
Cap hollow posts or tubes. Evidence suggests that this could be a pervasive problem, especially given that birds and other animals investigate cavities as potential nesting sites and would not be able to escape the smooth-walled interiors. More expensive caps can be purchased; however, relatively cheap solutions like filling cavities with soil, rocks and sand is effective.
Place or make ramps within ends of cattle guards. Water can collect in cattle guards (Texas gates) and may attract animals to the pits. Ramps provide an option to exit the pits.
Perform routine maintenance and remove any existing loose wire strands or bales. Loose wires increase the probability of entanglement. Wildlife have been documented to become entangled in loose wires and wire bales.
With financial support from the Fish and Wildlife Enhancement Fund, we removed or installed wildlife-friendly features on nearly 37 kilometres of fencing within our properties in 2020. Though we add new properties annually, our overall holdings remain relatively small compared to the total public and private lands within Manitoba. For the greatest impact on the landscape, we encourage other landowners to consider some of these same techniques.