Geotropic, hydrokinetic and random walking differ between sympatric tick species: the deer tick Ixodes scapularis and the lone star tick Ambylomma americanum

The black-legged tick –sometimes referred to as the deer tick— Ixodes scapularis and the lone star tick Ambylomma americanum are sympatric species whose distributions overlap both geographically and ecologically. Each species vectors a number of pathogens including the agents responsible for Lyme disease and ehrlichioses. We performed ethological observations of both species in five behavioral arenas focusing on geotropism and hydrokinesis. Adults of A. americanum showed positive geotropism by (a) walking down a precipice, (b) descending a wire, and (c) refusing to climb up a wall at the first encounter. In contrast, I. scapularis adults and most nymphs of both species showed negative geotropism in the same tests. Adults of both species and nymphs of A. americanum walked into the water while clinging to a cork, and even walked a distance beneath the surface of the water. On a servosphere, adults of A. americanum walked faster than I. scapularis adults, but I. scapularis spent more time walking. We discuss the importance of these attributes from behavioral ecology perspectives including previously reported notions of aggressiveness of tick species. The assessment of behavioral distinctness between these sympatric species will facilitate the design of experiments aimed at evaluations of attractants and repellents, and contribute to biorational control and surveillance strategies.