Mule deer (Odocoileus hemionus) are an economically important species to wildlife enterprises throughout New Mexico and the western United States, but populations are declining, limiting recreational and revenue potential to private and public wildlife managers. We documented body condition, survival, production of fawns, and trends in population size of a declining mule deer population on the Corona Range and Livestock Research Center (CRLRC), a multiple-use research ranch in east-central New Mexico owned by New Mexico State University. Mule deer females were in poor condition, characterized by accrual of little body fat or lean tissue (muscle mass) reserves. Annual female survival was 0.42, 0.78, and 0.71 during 2006 to 2008 and was related to poor body condition and precipitation. Survival of females was positively related to precipitation from January to June and April to June, seasons that coincide with conception-parturition and late gestation in deer. Survival also was positively related to increasing lean tissue (muscle) reserves. Malnutrition was the most common cause of death for adult females (n = 13 of 22). Fawn survival to weaning was positively related to increasing size of females, but not to any measure of seasonal or annual precipitation. Low survival and low productivity resulted in the CRLRC deer population declining from 539 to 191 during 2005 to 2008. Poor condition of deer was the result of both seasonal drought and a lack of quality forage. While drought will always decrease productivity of mule deer populations, survival may be maintained by managing for more drought-tolerant forage, which limit population declines during droughts.

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