Most of us don’t realize the damage done every year to fiber and to other wired networks by animals.
Squirrels. These cute rodents are the number one culprit for animal damage to aerial fiber. To a lesser degree, fiber owners report similar damage by rats and mice. Squirrels mainly chew on cables as a way to sharpen their teeth. Squirrel teeth grow up to 8 inches per year and if squirrels aren’t wearing their teeth down from their diet, they look for other things to chew. There has been speculation that squirrels prefer fiber to other cables due to some oil or compound used in the fiber manufacturing process that attracts them.
Before Level 3 was part of CenturyLink, they reported that 17% of their aerial fiber outages were caused by squirrels. A Google search turns up numerous network outages caused by squirrels.
Companies use a wide variety of techniques to try to protect from squirrel damage – but anybody that has ever put out a bird feeder knows how persistent squirrels can be. One deterrent is to use hardened cables that are a challenge for squirrels to chew through. However, there have been cases reported where squirrels partially chew through such cables and cause enough damage to allow in water and cause future damage.
A more common solution is some sort of add-on barriers to keep squirrels away from the cable. There are barrier devices that can be mounted on the pole to block squirrels from moving higher. There are also barriers that are mounted where cables meet a pole to keep the squirrels away from the fiber. There are companies that have tried more exotic solutions like deploying ultrasonic blasters to drive squirrels away from fiber. In other countries the fiber providers sometimes deploy poison or obnoxious chemicals to keep squirrels away from the fiber, but these techniques are frowned upon or illegal in the US.
Gophers. For buried fiber, the main animal culprit in parts of the US are pocket gophers. There are thirteen species of pocket gophers in the US that range from 5 to 13 inches in length. The two regions of the country with pocket gophers are the Midwest plains and the Southwest. Gophers live on plants and either eat roots or pull plants down through the soil.
Pocket gophers can cause considerable damage to buried fiber. These rodents will chew almost anything and there have been reported outages from gophers that chewed through gas, water, and buried electric lines. Gophers typically live between 6 and 12 inches below the surface and are a particular threat to buried drops.
There are several ways to protect against gophers. The best protection is to bury fiber deep enough to be out of gopher range, but that can add a lot of cost to buried drops. I have a few clients that bore drops rather than trench or vibrate them for this reason. Another protection is to enclose the fiber in a sheath that is over 3 inches in diameter. Anything that large and tubular is generally too big for a gopher to bite. Again, this is an expensive solution for buried drops. Another solution is to surround the buried fiber with 6 – 8 inches of gravel of at least 1-inch size – anything smaller gets pushed to the side by the gophers.
A recent blog by the fiber material vendor PPC highlights even more exotic animal damage to fiber. The most interesting example (and one that is easy to picture) is when farmers cut fiber while burying dead livestock. They typically bury dead animals where they find them, and if that’s in a right-of-way they can easily cut buried fiber.
PPC also reports that birds can do damage to aerial fiber. Large birds with sharp talons can create small cuts in the sheath and introduce water. Flocks of birds sitting on a fiber can cause sag and stretching of the fiber. I can remember when living in Florida seeing flocks of birds sitting shoulder-to-shoulder on cables and that has to add a lot of weight over a 200-foot span between poles.