US93 Bighorn Sheep Study: Distribution and Trans-Highway Movements of Desert Bighorn Sheep in Northwestern Arizona

摘要

Desert bighorn sheep were monitored via satellite telemetry, ground observations, and track beds between 2004 and 2006, primarily to determine distribution and movements relative to mileposts (MP) 3 to 17 of U.S. Highway 93 in the Black Mountains of northwestern Arizona. Bighorns were distributed and moved throughout the study area, but locations of trans-highway movements were not random. Construction of a highway bypass structure between MP 0 and 3 had no apparent effects on permeability of the right-of-way corridor to bighorns. Bighorns concentrated trans-highway movements in the area of proposed highway realignments between MP 3 and 17 at five locations. The research team identified five continuous, linear, elevated guideways (ridgelines) in this area where bighorns concentrated trans-highway movements. Specifically, these ridgelines were located near MP 3.3, 5.1, 7.7, 12.2, and 15.3. Eighty-two percent of highway crossings between MP 3 and 17 occurred near ridgelines at MP 3.3, 5.1, and 12.2, and the research team concluded highway crossing structures at these locations likely would promote highway permeability at a level ensuring genetic heterogeneity and vigor of the resident desert bighorn sheep population.