A numerical response of wolves to bison abundance in Wood Buffalo National Park, Canada

Abstract

The numerical response of predators to changing prey density is an important component of predator-prey dynamics. We examined factors influencing two indices of wolf (Canis lupus) abundance in Wood Buffalo National Park, Canada: historical wolf pelt harvests from 1970 to 1988 and sightings of wolves by park staff on survey flights from 1973 to 1991. We tested the effect of pelt price (adjusted to 1986-equivalent Canadian dollars), number of trappers, and bison (Bison bison) population size on wolf pelt returns for an 18-year period using a multiple linear regression model. We then tested the relationship between wolf sightings on survey flights and bison population size for an overlapping 19-year period. Wolf pelt price was a significant determinant of wolf harvest, whereas numbers of bison or trappers were not significant predictors of wolf harvest. However, there was a significant relationship between wolf sightings and bison population size. This analysis suggests that wolf population size was correlated with bison numbers, similar to the numerical response seen in other wolf-prey systems.