Date of Award:

2001

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Natural Resources

Department name when degree awarded

Fisheries and Wildlife

Advisor/Chair:

John A. Bissonette

Abstract

One-way escape gates and earthen escape ramps are structures used to enable deer to exit the highway right-of-way along fenced roads. I compared the use of one-way escape gates and earthen escape ramps by mule deer on two highways in Utah to determine if deer exhibited a preference for either structure. Results showed that earthen escape ramps were used by mule deer 8-11 times more frequently than one-way gates. Highway mortality data suggest that the installation of the escape ramps likely reduced mortality of mule deer in both study locations, because we could not attribute reductions in mortality to decreased population densities of mule deer in either location. Because they provide a topographic solution for exiting the right-of-way, escape ramps may reduce deer mortality along other game-fenced highways throughout the United States. Management recommendations that address the placement and spacing of escape ramps will help wildlife and highway personnel implement the use of these ramps in other locations.

A cost-benefit analysis was conducted to determine if the cost of ramp installation was offset within a reasonable time period by the monetary savings associated with reduced deer-vehicle collisions. The cost-effectiveness of installing the earthen escape ramps at both locations was determined by using the number of successful ramp crossings and potential deer mortality levels to generate projected monetary losses associated with varying mortality levels. The assumption was made that at least some of these deer that crossed successfully would have been involved in a deer-vehicle collision had the ramps not been in place. Six arbitrary levels of potential mortality (from 2% to 15%) were generated based on those assumptions. These percentages were multiplied by the number of successful deer crossings at each location to generate potential deer mortality numbers. The number of deer mortalities was then multiplied by the average economic loss of a deer-vehicle collision ($3,845) to obtain an estimate of the mitigated benefits of installing the ramps through 1999. These values were compared to the cost of installing ramps at each location to determine the amortization period.

Results showed that the cost of installation of earthen escape ramps is very rapidly offset by the benefits gained in deer survival and reduced automobile collisions. At the 2% mortality level, the cost of ramp installation in both locations was offset by the monetary savings associated with reduced deer-vehicle collisions by the second year. Heavy use of the escape ramps as well as reduction in mortality observed at both study sites indicate that the mitigation benefits may be much greater than those projected at the 2% mortality level. Installing earthen escape ramps on big-game fenced highways is a very cost-effective way to further reduce deer mortalities along roadways.

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