Climate or host availability: what determines the seasonal abundance of ticks?

Ticks can significantly affect the health and fitness of the host. Seasonal population dynamics of ticks play a vital role in disease transmission and the shaping of life-history traits of both tick and host. In this study, we examine the seasonal population dynamics of Ixodes hirsti in South Australia. For 2 years, we measured the prevalence and intensity of I. hirsti on passerines on Kangaroo Island. Ticks were present on birds from April to November and absent from December to March, with a peak in tick prevalence between June and September. The peak in tick abundance coincided with the host breeding season. Across the year, the most prominent fluctuations in tick abundance occurred in birds that were previously characterized as having high tick prevalence. Tick abundance on passerines fluctuated with host availability and climatic conditions: more ticks were present in months with high humidity and rainfall and low temperature. However, the relative influences of climate and host availability on tick presence were hard to separate.