The Journal of Wildlife Management; DOI: 10.1002/jwmg.640 Research Article Survival Probabilities of Adult Mongolian Gazelles KIRK A. OLSON,1,2 Department of Environmental Conservation, University of Massachusetts, Amherst, MA 01003, USA; and Smithsonian Conservation Biology Institute, National Zoological Park, 1500 Remount Road, Front Royal, VA 22630, USA ELISE A. LARSEN, Department of Biology, University of Maryland, College Park, MD 20742, USA THOMAS MUELLER, Department of Biology, University of Maryland, College Park, MD 20742, USA; and Biodiversity and Climate Research Centre (BiK-F), Senckenberg Gesellschaft fu¨r Naturforschung, and Goethe Universita¨t Frankfurt, Senckenberganlage, 25, 60325 Frankfurt (Main), Germany PETER LEIMGRUBER, Smithsonian Conservation Biology Institute, National Zoological Park, 1500 Remount Road, Front Royal, VA 22630, USA TODD K. FULLER, Department of Environmental Conservation, University of Massachusetts, Amherst, MA 01003, USA GEORGE B. SCHALLER,3 Wildlife Conservation Society, 2300 S Boulevard, Bronx, NY 10460, USA WILLIAM F. FAGAN, Department of Biology, University of Maryland, College Park, MD 20742, USA 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. Ó 2013 The Wildlife Society. KEY WORDS cause-specific mortality, cementum annuli, Mongolia, poaching, Procapra gutturosa, survival, temperate grassland, ungulate mortality, Weibull probability models. Mongolian gazelles (Procapra gutturosa) symbolize the other hunting (Wingard and Zahler 2006, Olson 2008). endless and unspoiled Mongolian steppe and, because of Even though Mongolian gazelles provide substantial their large, nomadic aggregations, constitute one of the ecosystem services through commercial harvest, subsistence world’s most impressive wildlife spectacles (Schaller 1998a, hunting, and ecotourism, management programs for the Olson et al. 2009). A recently published estimate of species remain minimal (Clark et al. 2006). population size is just over 1 million individuals; however, Once found from Buryatia and Tuva in Russia to Inner standardized, long-term monitoring efforts are lacking Mongolia and Heilongjiang in China, the gazelles’ (Milner-Gulland and Lhagvasuren 1998, Clark et al. geographic range has declined greatly because of over- 2006, Olson et al. 2011). The species has been heavily harvesting, border fencing, habitat loss, and rangeland harvested for decades, first under state-controlled manage- degradation (Lhagvasuren and Milner-Gulland 1997). To- ment practices (Milner-Gulland and Lhagvasuren 1998, day, Mongolian gazelles are found mainly in the eastern Reading et al. 1998) and more recently by poaching and grasslands and south Gobi regions of Mongolia. Smaller numbers occur in the border regions of Inner Mongolia, Heilongjiang, and southern Siberia, and a small population Received: 21 December 2012; Accepted: 22 September 2013 remains in an isolated region in western Mongolia (Wang et al. 1997, Clark et al. 2006). Up to 4.5 million Mongolian 1E-mail: kirk.olson@fauna-flora.org 2 gazelles may have existed around 1900. By the mid-1960s, Present address: Fauna & Flora International, Jupiter House, 4th severe range shrinkage and population declines were floor, Station Road, Cambridge CB1 2JD, UK 3Present address: Panthera, 8 W 40th Street, 18th floor, New York, NY occurring and attributed to heavy harvesting during World 10018, USA War II and the blocking of seasonal movements by the Olson et al. Survival of Adult Mongolian Gazelle 1 fenced Trans Mongolian Railroad (Hibbert 1968, Milner- Mongolian gazelle ranged from 0.90 during winter and 0.95 Gulland and Lhagvasuren 1998). The global status of in summer under normal weather summers, whereas during Mongolian gazelles is Least Threatened by the International severe winters, called dzud, survival rates were estimated to Union for Conservation of Nature (IUCN); however, be 0.82, and during dry summers 0.90 (Milner-Gulland and sustainable management practices have yet to be designed Lhagvasuren 1998). and implemented, and a number of additional threats have Human and livestock densities are greater in the western developed or increased in magnitude (Clark et al. 2006, regions of the eastern steppe than in the east, and gazelle Wingard and Zahler 2006, Mallon 2008). movements in the western region are believed to be restricted Monitoring known individuals through time affords an by the presence of the fenced Trans-Mongolian railway (Ito opportunity to determine annual survivorship and classify et al. 2005, 2008). The central region of the eastern steppe mortality events (Heisey and Fuller 1985). Understanding has human and livestock densities equivalent as those how different sources of mortality contribute to annual towards the west, but lacks major anthropogenic barriers, survival rates can help direct conservation resources to with the exception of the surrounding Mongolia-China activities most likely to benefit the species (Schaub and border fence. The easternmost region harbors the greatest Pradel 2004). As part of a long-term study of Mongolian number of gazelles, is the least populated, and provides the gazelle ecology, adult gazelles (>27 months) were captured closest match to the original steppe ecosystem (Olson and fitted with global positioning system (GPS)-tracking et al. 2011). collars to study their movement patterns and habitat needs (Mueller et al. 2011). We report the contributions of cause- METHODS specific mortality events to overall annual survivorship of During 5 separate years between 2002 and 2009 (2002–2003 adult Mongolian gazelles. We compare modeled median and 2007–2009), we used vehicles and drive nets in survival estimates with median age derived estimates from September to capture and collar 49 adult Mongolian tooth samples obtained during 2 state-sponsored harvest gazelles. After erecting capture nets in suitable terrain, events and a natural die-off (Schaller and Lhagvasuren 1998, gazelles were encouraged towards the nets using vehicles. Zahler et al. 2003). We discuss the implications of our Once entangled, the capture team moved quickly to findings for management of the Mongolian gazelle popula- immobilize gazelles by binding their hind and front legs tion and consequences for conservation efforts. using cotton rope and covering their eyes with an elastic sports bandage. Protocols for capturing and marking gazelles STUDY AREA (#22-02-03, #25-02-08, #28-02-08) were approved by the The eastern Mongolian steppe is one of the world’s largest University of Massachusetts at Amherst Institutional intact grassland ecosystems and contains the largest Animal Care and Use Committee. We then took blood concentration of gazelles in the world (from approx. 448 samples, fitted each adult female gazelle with a GPS tracking to 488N and 1078 to 1188 E, approx. 400,000 km2; device (Telonics, Mesa, AZ), and released them (Mueller Schaller 1998a, Olson et al. 2011). The eastern Mongolian et al. 2011). steppe is characterized by rolling hills, broad flat plains, and We captured gazelles at 3 locations in Mongolia’s eastern sparsely scattered small alkaline ponds and springs (Olson steppe defined by Olson et al. (2011): the western region (468 0 0 0 0 et al. 2010). Grasses (Stipa spp. and Leymus spp.) and forbs 45 N 1088 8 E), the central region (468 40 N 1108 40 E), and 0 0 (Allium spp. and Astragulus spp.) dominate steppe vegetation; the eastern region (478 05 N 1148 47 E). We concentrated shrubs (Artemesia spp. and Caragana spp.) are common, but our capture efforts in the eastern region (41 individuals) trees are rare (Gunin et al. 2000, Olson et al. 2010). Semi- supplemented with additional captures in the western (5) and nomadic pastoralists live throughout the region at very low central (3) regions. We collared females with the exception of densities (0.7 persons/km2; Milner-Gulland and 3 males captured in 2009 to evaluate an expandable collar. Lhagvasuren 1998). Expandable collars are necessary because male Mongolian Mongolian gazelles undertake long-distance movements