Effectiveness of Earthen Return Ramps in Reducing Big Game Highway Mortality in Utah

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USGS Utah Cooperative Fish and Wildlife Research Unit, Utah State University, Logan, Utah

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Conventional wisdom and highway practice across many states seemed to suggest that high (~2.4 m) ‘deer-proof’ fencing, coupled with underpasses are the mitigation of choice to prevent deer (and other ungulate) mortalities on U.S. highways. Our observations here in Utah and those elsewhere in the U.S. strongly suggested that few, if any, so called ‘deer-proof’ fences totally eliminated deer from accessing the Right-of Way (ROW) on fenced roads. In Sardine Canyon (US 91) in northern Utah, more than 50 deer were killed in one year on the road in a short section (MP 6.0- MP10) after the road was widened and fenced. This suggested to us that highway mitigation aimed at reducing deer-vehicle collisions needed to take into consideration measures that allowed deer to readily exit the highway ROW. We conducted a two-year study (October 1997- November 1999) to examine the effectiveness of earthen escape ramps in allowing deer to escape the highway ROW. We compared their performance with one-way steel escape gates

We identified two study sites in Utah with a history of high deer road kill and deer fencing, US 91 (MP 6 – MP 10) and US 40 (MP 4 – MP 13) as appropriate for study. During the period of the study (October 1997 – November 1999) we conducted regular spotlight counts to assess deer population trends at both sites. Concurrently, we recorded deer kills on both sites throughout the period. Earthen escape ramps were installed on US 91 in October 1997 (n = 9) and on US 40 between July and August 1998 (N = 7). We established track plots on each ramp in order to assess use by deer. Similarly, track plots were established at 10 one-way gates on US 91 and at 8 gates on US 40. At both sites, gates in the vicinity of the ramps were used. Ramps at the US 91 site were checked 61 times during the study and 188 successful crossings recorded. At the US 40 site, ramps were checked 42 times and 192 successful crossings recorded. Gates were checked 52 and 40 times during the study at the US 91 and US 40 sites, respectively. Fifteen of 45 (33.3%) deer at US 91 and 31 of 63 (49.2%) deer at US 40 passed through the gates successfully.

We compared the effectiveness of earthen escape ramps with one-way gates by standardizing their use into ‘ramp’ and ‘gate’ days. We then developed an index of use. At both sites, ramps were much more effective than gates in allowing deer to escape the ROW. Combined values from both sites suggest that earthen escape ramps were from approximately 8 to 11 times more effective than one-way gates. Our cost benefit analysis, using a deer valuation based on actual expenditures for deer hunting and adjusted for compensatory mortality, suggested that the cost of installing earthen escape ramps is rapidly offset by reduction in deer mortality. We recommend that earthen escape ramps be incorporated into mitigation when deer fencing is being considered for installation on Utah roads.

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