ABSTRACT
Animals foraging in patchy, non-renewing or slowly renewing environments must make decisions about how long to remain within a patch. Organisms can use heuristics (‘rules of thumb’) based on available information to decide when to leave the patch. Here, we investigated proximate patch-departure heuristics in two species of giant, brainless amoeba: the slime moulds Didymium bahiense and Physarum polycephalum. We explicitly tested the importance of information obtained through experience by eliminating chemosensory cues of patch quality. In P. polycephalum, patch departure was influenced by the consumption of high, and to a much lesser extent low, quality food items such that engulfing a food item increased patch-residency time. Physarum polycephalum also tended to forage for longer in darkened, ‘safe’ patches. In D. bahiense, engulfment of any food item increased patch residency irrespective of that food item's quality. Exposure to light had no effect on the patch-residency time of D. bahiense. Given that these organisms lack a brain, our results illustrate how the use of simple heuristics can give the impression that individuals make sophisticated foraging decisions.
Footnotes
Author contributions
T.L. conceived, designed and executed the experiments. T.L. and M.B. were both involved in interpreting the findings and drafting/revising the manuscript.
Funding
We would like to thank the Australian Research Council (DP110102998 to T.L. and DP0878924 and FT120100120 to M.B.), the Natural Sciences and Engineering Research Council of Canada (T.L.) and the Branco Weiss Society in Science Fellowship (T.L.) for financial support.
