Exponential distribution of velocities and power distribution of quiescent periods in the spontaneous movement patterns of three hunting spiders

Here, we investigate the spontaneous locomotor patterns in three spiders with different hunting strategies. The locomotor activity of adult wolf spiders Pardosa amentata, with a sit-and-move hunting strategy, has previously been demonstrated to follow strictly mathematical rules, with most time spent at lower velocities and exponentially decreasing time spent at increasing velocities. Likewise, they have an abundance of short quiescent (resting) periods following a power decay function towards longer quiescent periods. In the present study, we explored whether similar distributions were expressed in juveniles of P. amentata and in two other spider species with different hunting strategies: the sit-and-wait spider Xysticus cristatus and the actively searching sac spider Clubiona phragmitis. We found that all three spider species followed the same two general rules of movement. However, there were differences among the three species. On a logarithmic scale of exponential velocities and a double-logarithmic scale of the rest power decay function, the slopes of the lines for the three species differed. We propose that these differences reflect the behavioural and locomotor differences of the three hunting strategies. Furthermore, we compare our results with similar movement distributions in single cells, fruit flies, mice and even humans.