Searching strategy of the painted turtle Chrysemys picta across spatial scales

Abstract

The movement path made by an organism in search of a resource contributes strongly to the success of that search. But are similar search strategies used at very different spatial scales? Using painted turtles as our model organism, we ask (1) whether terrestrial search paths, both shape and rate, are similar at small (30 m) and large (>500 m) spatial scales, (2) whether those search paths are linear, and (3) what environmental conditions affect the shape of the search path? We found that movement paths at both small and large spatial scales were nearly straight and statistically indistinguishable from one another. The mean turning angles at small and large spatial scales were statistically similar and were best represented by an angle of 1.8°. Net displacement rates were, however, quite different between small- and large-scale paths. At small spatial scales, path shape and movement rate were most strongly affected by cloud cover and turtle size, respectively. Our results indicate that the shape of a search path is consistent over small and large spatial scales and gives support for extrapolating larger-scale path shape from small-scale observations. Net displacement rates, however, were scale dependent and thus caution must be taken in using behaviours detected at small scales to predict movement rates over larger areas. An unexpected result was that painted turtles did not follow drainages in search of aquatic habitat in this study system.