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Background Numerical responses of ticks to changes in densities of their hosts can be complex and apparently unpredictable. Manipulations even of deterministic models can produce counterintuitive results, including tick populations that either rise or fall under increasing host densities, depending on initial conditions. Methods In this paper I use an established simulation model to demonstrate a wide range of numerical responses to different scenarios of host changes, and to examine the basic mechanisms that drive them. Results The rate and direction of change of host densities affects the extent to which questing tick numbers reflect those of their hosts. Numerical responses differ profoundly between dynamic tick-host systems and those allowed to reach equilibrium. Conclusions The key to understanding tick-host dynamics is to understand the difference between 'real' and 'visible' tick populations. An appreciation of the implications of this difference - and of the conditions that influence it - will benefit the effective interpretation of field data. [ABSTRACT FROM AUTHOR]

Background The risk posed by ticks as vectors of disease is typically assessed by blanket-drag sampling of host-seeking individuals. Comparisons of peak abundance between plots -- either in order to establish their relative risk or to identify environmental correlates -- are often carried out by sampling on one or two occasions during the period of assumed peak tick activity. Methods This paper simulates this practice by 're-sampling' from model datasets derived from an empirical field study. Re-sample dates for each plot are guided by either the previous year's peak at the plot, or the previous year's peak at a similar, nearby plot. Results from single, double and three-weekly sampling regimes are compared. Results Sampling on single dates within a two-month window of assumed peak activity has the potential to introduce profound errors; sampling on two dates (double sampling) offers greater precision, but three-weekly sampling is the least biased. Conclusions The common practice of sampling for the abundance of host-seeking ticks on single dates in each plot-year should be strenuously avoided; it is recommended that field acarologists employ regular sampling throughout the year at intervals no greater than three weeks, for a variety of epidemiological studies. [ABSTRACT FROM AUTHOR]