Microclimate and habitat in relation to Ixodes scapularis (Acari: Ixodidae) populations on Long Point, Ontario, Canada.

The impact of microclimate and density of hosts for adult ticks on the density of Ixodes scapularis Say was evaluated within 4 habitats on Long Point, Ontario, from 1989-1992. During the period from May to September, mean weekly vapor pressure deficits were greater within the oak savannah and cottonwood dune habitats than at the maple forest and white pine habitats, which were similar. Vapor pressure deficit was likely the major factor affecting the survivorship of eggs and immature tricks in these habitats. Based on drag sampling, I. scapularis adults demonstrated peak activity in April and October of each year. The mean number of I. scapularis adults collected by dragging during the fall or in the spring did not differ significantly within each habitat. The mean number of adults collected also did not differ among tick cohorts within each habitat; however, significantly more adults were collected within the maple forest than in the white pine habitat. The mean number of I. scapularis adults per white-tailed deer, Odocoileus virginianus (Zimmerman), increased from 1989 to 1991 and then decreased in 1992. Significantly more adult I. scapularis infested deer were observed in 1990 than in 1989. Removal of deer in 1989 and 1990 resulted in a calculated decrease of > 100,000 fed female ticks. Although seasonal variation in microclimate within habitats was closely linked with tick survival and partly explains the differences in abundance of I. scapularis among habitats on Long Point, habitat utilization by deer was also a primary factor governing the local abundance of I. scapularis populations.