Ectoparasites typically exhibit aggregate distributions among their hosts; ticks feeding on mammalian hosts have been demonstrated to fit this pattern well. However, because ticks remain attached to their hosts as they feed, the number of ticks observed on an individual host at any given point in time include ticks that have been attached anywhere from zero to three days. To see if individual tick acquisition rates are correlated with tick burdens based on single observation counts, we estimated daily rates of larval Ixodes scapularis (black-legged tick) acquisition among five populations of Peromyscus leucopus, the white-footed mouse. For mice captured two days in a row, all ticks were counted and removed the first day, and new ticks acquired between release and capture the following day were counted. The number of ticks recorded the second day was regressed against the number of ticks recorded the first day.
Results/Conclusions
Throughout the summer and fall of 2008, we captured 260 P. leucopus on two consecutive nights, referred to as double captures. Of these, 169 were unique individuals; analysis was restricted to one randomly selected double capture per individual. The distributions of both single-observation counts and ticks acquired in a single day among these individuals fit a negative binomial distribution. The single-observation based number of ticks on an individual has a positive linear correlation with the daily rate of tick acquisition. This suggests that heterogeneity in tick distributions may be explained by variations in acquisition by host individual. Potential proximate mechanisms behind differences in tick acquisition among individuals are the spatial distributions of host-seeking ticks, combined with focal territory use by mice.