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Persistence of Different‐sized Populations: An Empirical Assessment of Rapid Extinctions in Bighorn Sheep
Author(s) -
BERGER JOEL
Publication year - 1990
Publication title -
conservation biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.2
H-Index - 222
eISSN - 1523-1739
pISSN - 0888-8892
DOI - 10.1111/j.1523-1739.1990.tb00271.x
Subject(s) - ovis canadensis , interspecific competition , persistence (discontinuity) , extinction (optical mineralogy) , competition (biology) , biology , ecology , population , predation , economic shortage , ovis , geography , population size , small population size , demography , habitat , paleontology , linguistics , philosophy , geotechnical engineering , sociology , government (linguistics) , engineering
Theory and simulation models suggest that small populations are more susceptible to extinction than large populations, yet assessment of this idea has been hampered by lack of an empirical base. I address the problem by asking how long different‐sized populations persist and present demographic and weather data spanning up to 70 years for 122 bighorn sheep ( Ovis canadensis ) populations in southwestern North America Analyses reveal that: (1) 100 percent of the populations with fewer than 50 individuals went extinct within 50 years; (2) populations with greater than 100 individuals persisted for up to 70 years; and (3) the rapid loss of populations was not likely to be caused by food shortages, severe weather, predation, or interspecific competition These data suggest that population size is a marker of persistence trajectories and they indicate that local extinction cannot be overcome because 50 individuals, even in the short term, are not a minimum viable population size for bighorn sheep.