A young mule deer buck met an untimely demise in this barbed-wire fence in northern Nevada. Ever increasing numbers of fences can cause both hidden mortality in mule deer and not so hidden mortality as seen above. The metabolic costs associated with navigating fences in and around mule deer habitats can be a significant hidden killer especially when the fences intersect animal movement corridors.
This article is the third and final in a series on mule deer populations in Nevada. It describes the effects of today’s urbanization and development on mule deer populations.
Nevada ’s tremendous population growth has affected mule deer populations in a way that is unapparent to most of us. Not only has the amount of land inhabited by humans crept into mule deer habitat, but commerce and urban development have disrupted the mule deer’s “commute” between their winter and summer homes, or seasonal migratory pattern. The cumulative effects of challenges mule deer face in migration can be an unseen killer.
The last installment in this series explained how Nevada’s human population should be credited for creating most of Nevada’s mule deer habitats. Presently, human population growth is likely to produce a consistent negative influence on most mule deer habitats in Nevada. The negative influences are twofold: loss and fragmentation of habitat, and the creation of impediments to natural migratory paths.
As we develop homes and businesses in mule deer habitat we find more deer in our yards, on our streets, and around our homes. Mule deer often persist in these environments but seldom thrive. “Urban” deer often show signs of poor body condition as a result of a diet consisting largely of ineffectual, nonnative forage.
Our housing developments and businesses, together with railroads, fences, highways, guardrails, open pits, heap leach pads, waste rock dumps and canals can all present obstacles to mule deer as they migrate from winter to summer ranges, and back. Some mule deer migrations exceed 100 miles in length. Mule deer have shown little adaptability with respect to altering their migration routes to avoid impediments, so will doggedly try to overcome these barriers. That effort alone can be the demise of a mule deer.
Fences, for example, kill deer in direct and indirect ways. Although most highway right-of-way and public land fences are constructed to meet specifications intended to reduce fence-related mortalities, many private land fences, including rangeland fences, do not. Entanglement occurs and mule deer are killed or suffer injuries that result in fatality. But fences also kill deer in indirect ways.
Mule deer have energy “budgets.” The best deposits are high-quality native forage. Withdrawals include the energy they need to simply exist, plus expenditures for migrating, mating, and nurturing fawns.
During a 100-mile migration, deer can easily encounter 60 or more fences. When encountering a fence, they often walk up and down the fence contemplating the best place to cross. They may stop and backtrack. Exacerbating the complications of fencing is the slope of the ground upon which the fence is constructed. A four-foot fence can effectively become an eight-foot fence to a deer on the downhill side. In this case deer have no choice but to look for another place to cross. Fences and other impediments eat up their precious energy and time budgets resulting in poor body condition and eventual starvation.
Since we’re not finding dead deer piled up around fences, most of us are unaware of the cumulative impacts fences and other impediments have on mule deer. Cooperation between municipal planners, developers, and private landowners is an essential step towards protecting mule deer habitat and migratory paths.
This information is taken from “ Nevada’s Mule Deer – Population Dynamics: Issues & Influences,” by Tony Wasley, available at Nevada Department of Wildlife offices for $10.00.
The Nevada Department of Wildlife is the state agency responsible for the restoration, protection and management of fish and wildlife resources, and the promotion of boating safety on Nevada’s waters. Wildlife offices are located in Las Vegas, Henderson, Winnemucca, Fallon, Elko, and Reno. For more information, contact the agency web site at www.ndow.org.
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