Quantitative analysis of spider locomotion employing computer-automated video tracking.

The locomotor activity of adult specimens of the wolf spider Pardosa amentata was measured in an open-field setup, using computer-automated colour object video tracking. The x,y coordinates of the animal in the digitized image of the test arena were recorded three times per second during four consecutive 12-h periods, alternating between white and red (lambda > 600 nm) illumination. Male spiders were significantly more locomotor active than female spiders under both lighting conditions. They walked, on average, twice the distance of females, employed higher velocities, and spent less time in quiescence. Both male and female P. amentata were significantly less active in red light (simulated dark environment) than in white light. The results also revealed that P. amentata administers its walking velocity and periods of quiescence according to consistent distributions, which can be approximated by simple mathematical expressions. It was found that this species spends exponentially decreasing time at increasing velocities. The number of quiescent periods, however, follow a power decay distribution at increasing quiescent period duration.