The Nature of Fences
By Eric R. Eaton:
There is nothing neutral about a fence. Like “No Trespassing” and “Beware of Dog” signs, they emphasize our disdain for strangers. They keep wildlife and suspicious people out; they keep pets and prisoners in, except when they don’t. Chain link, split rail, white picket, barbed wire, electrified, they all fail us. Nature sees fences as food, substrate, sometimes a tool, always as ephemeral. If there is one thing nature abhors more than a vacuum, it is a boundary. Looking at fences from nature’s perspective might lead us to choose what materials to use, or help us decide whether we want a fence at all.
Fences can be interpreted as symbols of colonialism, privilege, and exclusion. Visible borders attest to the breadth of one’s real estate and affluence. Closer to home, literally, fences may indicate fear, offering another layer of protection from “others.” We surround prized plants with fence-like barriers to discourage rabbits, rodents, and deer because we view our gardens as separate from nature. Fences proclaim ownership, but this is not a natural concept.
Territoriality is natural, but impermanent. The scent-marking feline will eventually have his territory usurped by a rival, or will otherwise abandon the area eventually. Society frowns upon humans pissing out boundaries, but we have no perfect alternative. Natural boundaries shift over time. Even rivers. We try to manage them with fences of another sort: dams and locks, to no avail. It may be futile to engineer an artificial divide in light of the transient aspects of nature.
Some fences are friendlier than others, but none are without impact. As a rule, the smaller the area you enclose, the better, allowing wildlife safe passage between natural habitats, and resources like water, forage, and cover. Avoid woven-wire fencing, as it can be a fatal entanglement hazard. Fencing material not easily seen is a collision hazard. Loose wires, wires spaced too closely together, wires too close to the ground, and fences over forty-two inches in height are wildlife-unfriendly scenarios at a larger landscape scale. Do not accidentally funnel wildlife towards busy roads. An opening at the corner of a fence affords trapped wildlife an easier escape than a gate somewhere in the middle.
Almost no fencing solution will keep out digging animals like skunks, or subterranean nuisances like gophers (there are no moles in Colorado, btw). Placing flagstone around the perimeter of sheds and along garden fence lines will help deter the diggers. Bending the bottom two feet of wire mesh fencing outward into an “apron” (sometimes burying it) is another strategy.
Solid wooden “privacy fences” can be attractive and rustic, but may throw shade on plants that require full sun (or on icy sidewalks) and block lines of sight for wildlife. Rot erodes them from below, termites eat them. (Yes, in Colorado.) Freezing and thawing warps unfinished planks, and algae, lichens, and mosses gain a foothold, eventually weakening them. Winds will flatten wooden fences.
That said, the rough texture of unpainted wood makes it easily climbable by wildlife, from insects to… fence lizards. Birds perch easily atop them. Wooden fences are an avenue for squirrels but a barrier to deer. Knotholes may be exploited by beneficial, solitary, cavity-nesting bees or wasps. Social yellowjackets and paper wasps, which kill many pest insects, scrape the surface of unfinished wood to manufacture “paper” for their nests. Lizards, snakes, and butterflies and other insects utilize wood fences for basking. Baby spiders climb to the peaks of fences and “balloon” to other places by releasing streams of silk into the wind.
People, especially those new to mountain and foothill communities, tend to put up fencing along their property lines. If the property contains important habitat and the fence excludes wildlife, the animals lose food, water, resting areas, and travel corridors. (Colorado Parks & Wildlifeˆ)
Wire fences are more permeable to smaller wildlife, if animals can see them. Topping the fence with thicker, colored wire, or a PVC cover, helps, as does flagging. Deer are discouraged by fences that are wider at the base. A leaning or staggered picket fence, or a fence in tandem with shrubbery, is a good deer deterrent.
Insects use wires and posts as perches, as do birds. Shrikes use barbed wire to impale prey, caching it there for later consumption. Vines climb most fences easily, but are especially adept at twining themselves around chain link. Winds may or may not affect wire fences negatively, but in places where Russian Thistle abounds, a good blow can festoon barbed wire with countless tumbleweeds. A sound alternative to barbed wire is high-tensile fencing that requires less maintenance and repair, fewer posts, and is resilient to impacts such as tree falls.
Wrought iron fences are decorative and sturdy, at least until weathering rusts them, but they can and do eviscerate wildlife attempting to jump them, and trap other wildlife (or dogs ) that try to squeeze through. Such fences also seem to invite vehicular collisions, and at any rate are costly to repair.
A “living fence” can be created by planting native shrubs or trees like willow and alder to form a hedgerow. Roses and brambles are living barbed wire. This strategy can invite desirable resident songbirds and pollinating insects, while functioning as a barrier to large mammals.
Colorado Parks and Wildlife has an excellent document about wildlife-friendly fencing at this link: https://cpw.state.co.us/Documents/LandWater/PrivateLandPrograms/FencingWithWildlifeInMind.pdf. Remember also that fencing is resource-intensive, so choose wisely, and select re-purposed material if and when possible. You might consider an alternative such as a hedge, a row of trees, or even a low rock wall or closely-spaced boulders. Please be mindful of the need and purpose when choosing a fence. Wildlife thanks you in advance.
Eric R. Eaton is principal author of the Kaufman Field Guide to Insects of North America and writes the blog “Bug Eric.”