Great Basin Naturalist


Eastern cottontail rabbits, Sylvilagus floridanus, introduced into Linn County, Oregon, in 1941, occupied 378.1 km2 in 1953, 637.7 km2 in 1970, and 1.501.9 km2 in 1980. Hiatuses within the range were related to absence of adequate coverts on conifer-dominated ridge tops and in intensively cultivated areas. Flooding of riparian zones seven times during the first 12 years after introduction and three times during the 17-year interval between the first and second surveys (especially the devastating floods of December 1964 and January 1965) was believed to have retarded dispersal or periodically reduced the area occupied. Flood-control dams constructed between 1941 and 1968 on drainage systems that affect the area limited floods to two winters since 1965 and were believed responsible for cottontails extending their range within the county nearly two and one-half fold since 1970. The absence of burrow-constructing associated species was believed relatively insignificant in retarding dispersal. Removal of brushy coverts, particularly by agricultural practices, tended to increase the size of unoccupied areas within the 1970 range of the species.