Seasonal dynamics of American dog tick, Dermacentor variabilis (Say), populations in southwestern Nova Scotia

Abstract

Seasonal activity and host relationships of the American dog tick in three areas of southwestern Nova Scotia are described from 1973 to 1975. The majority of Dermacentor variabilis individuals undergo a 2-year life cycle in Nova Scotia. Unfed adults and larvae are the two main overwintering stages. Adult tick activity extends from April to mid-August, with one population peak during May and (or) June. Peak adult densities, based on mark–recapture methods, were estimated between 7887 and 20 909 ticks per hectare at two areas during 1974 and 1975. Larval activity extending from late April to September was usually bimodal. The main peak of overwintered larvae engorged during June, while a second peak of recently hatched larvae, depending on weather conditions, usually occurred during August. The main relative larval density during the dominant spring peak was 3.95 larvae per host. Nymphal populations occurred between May and August with the unimodal activity pattern averaging 3.85 nymphs per host at the peak during June. The voles Microtus pennsylvanicus and Clethrionomys gapperi sustained almost 80% of all larvae and over 85% of all nymphs collected from mammal hosts. The snowshoe hare, Lepus americanus, and the jumping mouse, Zapus hudsonius, also harbored substantial numbers of immature ticks. Dermacentor variabilis life cycles studied in Massachusetts, Virginia, and Nova Scotia are compared.