PARASITIZATION OF MEADOW VOLES, MICROTUS PENNSYLVANICUS (ORD), BY AMERICAN DOG TICKS, DERMACENTOR VARIABILIS (SAY), AND ADULT TICK MOVEMENT DURING HIGH HOST DENSITY¹

The numbers of host-seeking adult American dog ticks, Dermacentor variabilis (Say), in a sweet gum field in Maryland reflected changes in the population density of a host species, the meadow vole, Microtus pennsylvanicus (Ord), which within 1.5 yr fell from an estimated 157 to 8 voles on a 0.8 ha grid. During high vole density, there was no significant difference (P > 0.05) in tick burdens between sexes on an annual basis. Juvenile and subadult voles (< 33 g) harbored significantly fewer D. variabilis larvae and nymphs than did mature voles (> 33 g) on an annual basis. However, during periods of both peak host-seeking activity by D. variabilis larvae and nymphs and high host density nearly all the voles examined were infested. There was no evidence of a relationship between weight of adult voles and likelihood of parasitization by D. variabilis during months of moderate tick host-seeking activity. Of 163 adult D. variabilis recaptured ≥ one week after marking, 86 (52.7%) had moved > 3.8 m, 59 (36.2%) > 5.3 m.