Fencing with Wildlife in Mind

Fencing with Wildlife in Mind

During the time of western explorer John C. Fremont, his diaries were full of descriptions of large herds of deer, elk, grizzlies, black bears, mountain lions and pronghorn throughout Colorado. Wildlife needs to travel through these areas to find food, water, and shelter. Fences, loss of habitat from human development and even extreme weather conditions have played a role in preventing this natural migration for food, water, and shelter and have caused unnecessary loss of animal lives. In addition to designating boundaries of ownership, protecting special areas, and keeping cattle in or out of property, fences have a big role in preventing or allowing Colorado’s wildlife an opportunity to do what they do best…to be a sustainable part of our great Colorado landscape. 

Fences that are a problem to wildlife are:  

• Too high to jump over, 
• Too low to crawl under, 
• Too loose that legs get tangled,  
• Woven wire that traps calves or fawns,  
• Closely spaced wires that also tangle legs of jumping deer and elk,  
• Wires that are hard for wildlife to see, any kind of fence that makes a complete barrier  

Elk and deer go over fences and jump with their back feet forward. This means that their legs can get caught jumping over a fence. The result is a desperate and painful death. Fawns or calves that are unable to jump a high fence and unable to crawl under, find themselves separated from their mother and then become victims of predators, vehicles, or starvation. 

A woven wire fence with strands of barbed wire on the top becomes one of the most deadly types of fences since animals are unable to go over and cannot go under. Researchers at Utah State University completed a study of wildlife mortality along more than 600 miles of fences in 2005 and 2006 and some of their key findings include:  

• Juveniles are eight times more likely to die in fences than adults.  
• Woven-wire fence topped with a single strand of barbed-wire was the most lethal fence type; ungulate’s legs are easily tangled and snared between the top barbed wire and the woven base.  
• Fences higher than 40” accounted for 70% of all mortalities.  
• Fawn carcasses made up 90% of those found. These young animals, unable to cross with their mothers became caught in the fence and died there. 

Ideal Wildlife Fence

• The friendliest fences for wildlife are ones which are highly visible and allow animals to easily jump over or go under the fences. Colorado Parks and Wildlife recommends the following:  
  • Fencing wire placed on the side of the fence posts where the livestock is located  
  • Smooth wire on the top and on the bottom
  • Top wire height of 42”  
  • At least 12” between top two wires  
  • At least 16” between the ground and the bottom wire 
  • For sheep and goats, a 12” smooth wire may be the best method to keep in your livestock

Consider high tensile wire

This is a very strong 12.5 gauge wire that starts elongating at 1,350 pounds of pressure and can spring back to it’s natural shape. It has a breaking point at 1650 pounds of pressure. High tensile wire is less expensive to install and easier to maintain than traditional barbed-wire fences. High tensile wire can be strung up to 100 feet between posts.  

Different types of fences for different wildlife species

Depending on where you are located in Colorado, wildlife species may be limited by the type of fencing you provide. Not all fences require the same amount of wire or materials. A 3 strand, high tensile wire is effective to keep livestock in and allow bighorn sheep to jump through or crawl under.  

Seasonal electric fence may be more appropriate to allow elk and other ungulates where permanent fencing is not desired or feasible. A 2-wire fence may be enough for this situations and can be laid down when the fence is not in use.  

Drop-down fences may be implemented to provide crossing on areas where there are signs of wildlife passage such as game trails, stream corridors or gullies. Where cattle or horses share pastures with pronghorn, a PVC underpass, also known as a “goat bar” can be created by gathering the two bottom wires inside a PVC pipe to allow more space for pronghorn to crawl under but still remain effective at keeping horses and cattle in.  

Getting a good assessment of what animals share your land is key to designing the best fence that is respectful to wildlife in Colorado. To learn more about different types of fences you can download the “Landowner’s Guide to Wildlife Friendly Fences” and consult with your local NRCS agents to determine what types of wildlife may be present in your area.