EXTINCTION OF MAMMAL POPULATIONS IN WESTERN NORTH-AMERICAN NATIONAL-PARKS

Patterns of local extinction of mammal populations in western North Am erican parks were examined in relation to current biogeographic and po pulation lifetime models. The analysis was based on species sighting r ecords as of 1989. While western North American pants are obviously no t true Isolates, patterns of mammal extinction in them are nonetheless consistent with two predictions of the land-bridge island hypothesis. First, the number of extinctions hers exceeded the number of coloniza tions since park establishment, and, second the rate of extinction is inversely related to park area. Factors influencing the lifetime of ma mmal populations were evaluated using a stepwise multivariate survival analysis procedure for censored data Survival time for mammal populat ions was positively related to estimated initial population size. Afte r accounting for population size, species within the order Lagomorpha were particularly prone to extinction. Finally, after controlling for population size and taxon variation survival time was positively relat ed to age of maturity, indicating that species with longer generation times-age of maturity and generation time are highly correlated in mam mals-persist longer in absolute time.