Survival probabilities of adult Mongolian gazelles

Abstract

Mongolian gazelles are Central Asia's most abundant plains ungulate and an iconic symbol of large unfragmented grasslands. Despite a long history of commercial harvesting and subsistence hunting by herding households, adult gazelle demographic data is almost non-existent. We calculated cause-specific mortality rates for 49 adult gazelles collared with a global positioning system. Exponential models provided better fits to survival distributions from collared gazelles than did either Weibull or Gompertz models, and yielded an overall estimated annual mortality risk of 36%. The estimated daily hazard rate from human-caused mortality was 30% greater than the hazard rate due to natural mortality alone. Estimated median lifespan of adult gazelles was just 4 years, which concurred with age data taken from incisor cementum annuli obtained from harvested animals and from a natural mass mortality. For gazelles that have already reached adulthood, in the absence of hunting mortality, the estimated median lifespan of collared gazelles increased from 4 years to 8 years. Survivorship estimates from the complete telemetry dataset (including both natural and human-caused mortality sources) yielded lifespan estimates in line with greatly shortened lifespans evident during periods of heightened mortality, whether from a mass-mortality event or commercial hunting. When compared to earlier population models for the species, our results suggest current survival rates based on measures of natural and human-caused mortality will not support a stable population. © 2013 The Wildlife Society.