Spontaneous movement behaviour in spiders (Araneae) with different hunting strategies

摘要

The prey choices of predators are determined, in part, by their hunting strategies. The sit-and-wait and the actively searching strategies seem designed for active and stationary prey, respectively. A supposedly intermediate strategy, the saltatory or sit-and-move strategy, combines sitting still, scanning for prey with frequent moves to new scanning sites. We tested the hypothesis that the spontaneous movements of predators, i.e. activity performed in constant conditions in the laboratory, reflect their hunting strategy. We compared the crab spider Xysticus cristatus (sit-and-wait), the sac spider Clubiona phragmitis (active hunting) and the wolf spider Pardosa amentata (sit-and-move). We used automatic video tracking throughout 6 h during both light and dark conditions to quantify movement parameters: time in movement/rest; total distance moved, maximal velocity; mean velocity during movement; number of stops, longest rest period; and turn rate and turn bias. Xysticus and Clubiona confirmed predictions, but Pardosa showed a combination of movement parameters that was not intermediate between the other two. We suggest the existence of a sit-and-wait/sit-and-move continuum with varying proportions of sitting and moving, characterized by scanning for prey from a resting position, whereas the active searching strategy is distinct owing to detection of prey while the predator is moving.