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Planning the Great Western Extension Around Pronghorn Movements


By this point we all know that wildlife and highways don’t mix well.  This is evident from the multitude of remains from wildlife-vehicle collisions, or road-kill, that litter our roadways.  While this is a significant aspect of the difficulties associated with our transportation corridors, the less visible impacts are potentially more problematic for wildlife populations.  Loss of habitat to roads and the development that follows with them is a serious threat facing many species today.  Considering the degree of habitat loss already experienced and potential loss to future development, the greatest concern in these wildlife-highway interactions is the fragmentation of the remaining habitat leaving areas too small to sustain wildlife populations.

Many once large, open blocks of wild-lands in Arizona are already degraded due to the isolation imposed by roads built in the last 100 years.  Even with Arizona’s slowed population growth (human) and reduced funds for expansion and improvement, all predictions are for increased traffic volume on wider and more numerous roads and highways.  This can seem quite daunting for Arizona’s wildlife from many perspectives.  But, if we choose to view these transportation infrastructure improvements as an opportunity rather than just a threat, we can take advantage and not only limit further fragmentation, but reduce existing impacts in many systems.

Since 2001, the AGFD Research Branch has been working with the Arizona Department of Transportation and the Federal Highways Administration to mitigate highway effects on various projects involving the improvement of existing Arizona highways. This study stands apart from those as one of the first collaborations for mitigating an impending roadway in an area where no road exists.  This collaboration is strengthened by the participation of the county and local municipalities.  As members of Central Yavapai’s Metropolitan Planning Organization (CYMPO), they have joined in the effort to reduce the impact of this new road on local pronghorn.



The Great Western Extension will connect Prescott Valley to Chino Valley providing an alternative route to SR 89 & SR89A.  The focal area of observation extends from Ernest A. Love Airfield, at the interchange of these two highways, about six miles to the north and six miles to the east.



The Department is using a two-step approach to develop recommendations on the construction of the Great Western Extension.


  1. Collect Movement Data:  In September 2009, the Department deployed 10 Global  Positioning System (GPS) collars on pronghorn within and around the proposed highway footprints.  The GPS collars collect point locations on individual animals every two hours during periods of pronghorn activity.  These collars will collect >33,000 GPS locations by late fall 2010.
  1. Assess Movements:  These specialized collars upload their data to a private website, allowing biologists to monitor pronghorn movements at something approaching real-time.  When sufficient data is obtained, the point locations will be connected and the resulting movements will be overlaid on the projected roadway footprint.  The projected path will be broken down into short segments and crossing potentials will be calculated according to the concentration of intersections with pronghorn movements.

This location and movement information will be the basis for recommendations likely to include the incorporation and placement of crossing structures along the pending roadway.  Based on behavioral characteristics of pronghorn and existing literature, the recommended design of such mitigating features will be open and unobtrusive.  This could translate to overpass structures, which would allow wildlife to pass over the highway; or elevated viaducts, which would allow wildlife to pass under expansive bridges, which bear the roadway.


This unique opportunity has substantial direct and indirect benefits.  While the primary objective of this project is a permeable roadway and intact habitat, we can use the information we are collecting as a baseline for assessing the effectiveness of mitigation measures that are eventually applied.  This will help to maintain the integrity of this grassland habitat for pronghorn and other wildlife and allow for improved alleviation of future highway impacts.


Related Links - Wildlife - Highway Projects in Arizona:

How Did the Pronghorn Cross the Road? (U.S. Highway 89)

Wildlife Interactions Along State Route 64

An Evaluation of Bighorn Sheep Movements Along US Highway 191 and Morenci Mine

Desert Bighorn Sheep Use of Crossing Structures Along State Route 68

Efforts to Maintain Desert Bighorn Sheep Movement Corridors Across U.S. Highway 93 Near Hoover Dam

Interstate 40 and Elk: When Vehicles and Animals Collide

Elk Along Interstate 17: A closer Look at Elk-Highway Relationships

State Route 260 “Elk Crosswalk”

Comprehensive Approach to Wildlife Protection on State Route 260


Video Links - Wildlife - Highway Projects in Arizona:

Arizona Highway 93 Bighorn Sheep Project

Elk Crossing Safe Passage Highway (Elk and Sheep)

Elk Collaring: Catch an Elk

Safe Passage part 1 of 2 (State Route 260)

Safe Passage part 2 of 2 (State Route 260)

For more information contact:

Scott Sprague, Arizona Game and Fish Department
5000 W. Carefree Highway, Phoenix, AZ 85023

Jeff Gagnon, Arizona Game and Fish Department
5000 W. Carefree Highway, Phoenix, AZ 85023

Trevor Buhr, Arizona Game and Fish Department
5000 W. Carefree Highway, Phoenix, AZ 85023

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