Abundance of Ticks (Acari: Ixodidae) Infesting the Western Fence Lizard, Sceloporus Occidentalis, in Relation to Environmental Factors

We examined the impact of environmental characteristics, such as habitat type, topographic exposure and presence of leaf litter, on the abundance of Ixodes pacificus ticks infesting the western fence lizard (Sceloporus occidentalis) at the University of California Hopland Research and Extension Center (HREC), Mendocino County, California. A total of 383 adult lizards were slip-noosed and examined for tick infestation in April and May 1998. At least 94% of the lizards were infested by ticks and at least 20% of the females and 33% of the males carried > 15 ticks. This intensive utilization of western fence lizards (which do not serve as natural reservoirs for Lyme disease spirochetes) by subadult ticks, is probably the primary reason for the low prevalence of infection with Borrelia burgdorferi in I. pacificus nymphs and adults previously recorded at the HREC. Tick loads were higher on male than female lizards. Also, male lizards were generally more heavily infested in late April than in late May. The prevalence of tick infestation exceeded 88% in all habitat types but males collected in woodland and grass/woodland edges had higher tick loads than those collected in open grassland. Male lizards captured in open, exposed grassland tended to carry heavier tick loads in northern/eastern, as compared to southern/western, exposures, and when leaf litter was present.