Because of patch depletion, there comes a time after entering a patch when the forager should abandon the patch in favor of finding another. I am interested in what information influences the decision to leave a patch and how the information is used. In the past, I and my associates have studied patch departure decisions of blue jays using open economy, operant simulations of foraging. During a typical experiment, food-deprived jays would forage for one or two sessions per day, could exploit a depleting and a nondepleting patch, and would receive supplemental food later in the day to keep body weights consistent over days. A jay foraging in the wild, however, is not artificially deprived, forages for many bouts per day, chooses from multiple depleting patches, and must earn all of its food through foraging so that its weight varies with foraging success. I devised a combination of apparatus and procedure that used a closed economy system as its basis in order to test patch departure decisions under more realistic conditions. A jay foraged in a large operant chamber for multiple sessions per day, choosing from many depleting patches, and earning all of its food through its work (the defining characteristic of a closed economy). The initial experiment showed that the general approach was not only viable but healthier for the jays than open economy procedures. During the second experiment, the patches held differing numbers of prey but had equal prey densities. The jays relied on a combination of the number of prey found and run of bad luck (ROBL) durations to decide when to leave patches. These results were consistent with earlier findings. During the third experiment, the patches held equal numbers of prey but differed in prey densities. The jays used a combined departure rule (prey number and ROBLs) only at medium density, relying only on ROBL durations at high densities. The results showed that the jays' departure rules were largely density dependent and were sensitive enough to information within patches to achieve efficient foraging yet flexible enough to adapt to changing environments.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-2661 |
| Date | 01 January 1992 |
| Creators | Clements, Kevin Charles |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
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