Ticks are vectors for several zoonotic diseases, including Lyme disease, the main vector-borne disease in the United States. Ticks depend on vertebrate hosts for blood meals and movement, indicating that host use of the landscape would likely impact the distribution of ticks. In order to explore this process, I built a preliminary agent-based model using NetLogo. The main objective of the model is to determine if occupancy and percolation will affect deer-tick encounter rate and thus, tick density. Landscapes contained two types of patches, those containing good deer habitat and those with poor deer habitat were simulated in R using the secr package. Each landscape had a given percolation (aggregation, range: 0.15, 0.35, 0.55) of habitat patches and the proportion of good vs. poor habitat patches (occupancy, range: 0.1, 0.5, 0.9). Deer preferentially spent time in patches containing habitat. I ran 100 simulations for each type of landscape, in hourly time-steps for a duration of 60 days. I compared the final tick densities in habitat patches of each landscape using non-parametric Kruskal Wallis tests.
Results/Conclusions
Landscapes with low habitat occupancy exhibited the highest final tick densities in their good habitat-containing patches (p < 0.001). Percolation of good habitat patches did not have a significant impact on their final tick densities (p = 0.25). These results could be explained by the fact that when fewer habitat patches are available for deer, the same patch will be used more heavily than if there were many other patches available for use, contributing to aggregation of ticks in those patches. However, because deer in my model have a low chance of leaving a suitable patch once they reach it, deer movement won’t be impacted by the quality of habitat in the surrounding patches. In reality, deer movement may be influenced by surrounding patch quality. Additionally, deer may repeatedly exploit the same patches that they have previously visited, and know contain resources. Despite these caveats, my model is a useful tool for examining how landscape features impact tick densities via influence on host movement.