Movements and Survival of Adult Mule Deer Bucks in a Wildlife Enterprise Trophy Ranching Context

Abstract

Ranch economics are increasingly dependent upon wildlife enterprises throughout the arid Southwestern USA and Mexico, and mule deer (Odocoileus hemionus) are perhaps the most economically important species in the region. Because significant investments by landowners are necessary for trophy management (i.e., high adult sex [buck:doe] ratio, high buck survival, and advanced [older] buck age structure), loss of bucks to adjacent properties and increased mortality on ranches (both a potential consequence of more intense competition among deer under trophy management) could represent significant disincentives to managers. Hence, we evaluated the movements and survival of adult bucks in a ranch context in northeastern New Mexico, USA, to evaluate these concerns. We found that both concerns were warranted, especially for small ranching enterprises. Despite small home ranges (16.0 km²) and core areas (4.4 km²) due to intensive management for quality deer habitat, deer spent ca. 40% of their time on adjacent properties regardless of season, and half of deer with >50% of their annual ranges on adjacent properties were harvested there. Similarly, low body condition postrut predisposed all age (year)-classes of bucks to nonharvest mortality, likely an unavoidable consequence of trophy management. The most important consideration with respect to off-ranch movements is ranch size; properties < 4× larger than adult buck home ranges in arid Southwestern environments should question if investment in trophy buck production is viable. For ranches lacking intensive deer habitat improvement programs, adult buck home ranges are likely > 20 km², suggesting a size of ≥ 80 km² for ranches to ensure that a significant proportion of adult bucks are full-time residents, and hence allow managers to realize returns from trophy management.