Impacts of chronic wasting disease on a low density mule deer (Odocoileus hemionus) population in the San Andres Mountains, Chihuahuan Desert, New Mexico

Abstract

Chronic wasting disease (CWD), a contagious neurodegenerative disease of cervids, is becoming increasingly prevalent in the arid Southwest including the Chihuahuan Desert ecoregion. Population effects of CWD are uncertain, particularly in arid environments, as previous work has been on relatively high density deer populations in semi-arid or temperate environments. In 2002, CWD was detected in a low density mule deer (Odocoileus hemionus) population in the arid San Andres Mountains, a Chihuahuan Desert range in southern New Mexico. We determined prevalence and distribution of CWD, and mortality and movements of deer, to assess the potential impact on low density deer populations in arid environments. Repeated seasonal primarily ante-mortem sampling found stable prevalence of 0.000–0.091, 2003–2008. Annual CWD mortality rate was <0.02, including deer that were culled. Monitoring of adult radio-collared deer showed no dispersal movements away from home ranges, with maximum movements of ≤20 km; similarly, no juveniles dispersed from maternal ranges. Distribution of infected deer was strongly related to presence of other infected deer. Annual survival rates of mule deer and population rate-of-increase suggested little effect of CWD on population-level mortality given observed prevalence. Transmission and reservoirs of CWD in the SAM were likely limited by low deer densities, patchy distribution, and environmental characteristics (i.e., low clay content of soils) unfavorable to prion persistence, characteristics that are typical of most mule deer populations in the Chihuahuan Desert ecoregion.