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By making field observations on the movement pattern of the agrobiont
wolf spider Pardosa agrestis at two spatiotemporal scales, we explored how
fine-scale foraging movements scale up to medium-scale habitat use by the
spiders. For fine-scale observations, we followed individuals for several
metres and for up to 1-2h. For medium-scale observations we used marking
and recapture in live-trapping pitfall grids, which allowed us to detect
movements up to 70m and for 4 weeks. The analysis of fine-scale movement
indicated that spiders followed a 'sit-and-move' foraging strategy, which
consisted of variable periods of waiting (mean 2.5min) and brief bouts of
movements between the waiting sites. Spiders spent over 90% of the total
observation time waiting. Prey capture (or capture attempts) was initiated
only from waiting sites. Movement between consecutive waiting sites was
more directional than predicted by the correlated random walk model. At
medium (2-day) timescales the mean displacement of marked spiders was 7.4m.
Simulations suggested that such a displacement could be achieved if
movement observed at the fine scale followed a random path for 2 days. We
concluded that movement became less directional with increasing scale. Such
a phenomenon might be related to avoidance of revisiting food patches
locally and an efficient sampling of the habitat at higher scales. High
movement activity in a species that is primarily adapted to ephemeral
habitats might increase its likelihood of colonizing new habitat patches.
Copyright 2003 The Association for the Study of Animal Behaviour. Published
by Elsevier Ltd. All rights reserved.
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