NEAR-EXTINCTION OF PORCUPINES BY MOUNTAIN LIONS AND CONSEQUENCES OF ECOSYSTEM CHANGE IN THE GREAT-BASIN DESERT

In North America's Great Basin Desert changes in plant communities tha t occurred after the introduction of domestic livestock in the late 18 00s resulted in the irruption of mule deer (Ocodoileus hemionus) and e xpansion of mountain lions (Felis concolor). We report on a situation in which mountain lion predation caused the near-extinction of another native species, porcupines (Erethizon dorsatum). We used demographic information collected over 8 years on an individually identified popul ation and long term climatic data in a stochastic population model to examine the hypothesis that predation and not weather-induced starvati on or random population fluctuations threatened the persistence of a n aturally small population of porcupines. Whether drought-related reduc tions in mule deer densities induced mountain lions to prey on porcupi nes is unclear, but our results suggest predation and not climatic con ditions caused the decline of a once robust population of over 80 to < 5 animals in only 3 years. These data represent an unusual case in whi ch predation by a native predator caused the near-extinction of a nati ve prey species, suggesting that one unforeseen consequence of ecosyst em change in western North America may be the impending loss of small, native vertebrate populations.