Patch use under predation hazard: effects of the red imported fire ant on deer mice foraging behavior
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I compared patch use patterns of deer mice foraging in the presence and absence of a non-conventional predation hazard, red imported fire ants. Deer mice foraged for 60 min in an experimental arena containing two rich and two poor resource patches. All patches either had fire ants or did not have fire ants, and were filled with 5 or 16 whole sunflower seeds mixed in with 250 ml sand. Foraging strategy was identified by examining two aspects of patch use: density-dependence of resource harvest and over/underuse of rich patches relative to poor. Deer mice switched from a fixed search time strategy in the absence of fire ants to a Bayesian strategy in their presence. Resource harvest was density-independent in the absence of fire ants, meaning the mice harvested the same proportion of seeds from rich and poor patches. In the presence of fire ants, mice biased effort toward rich patches, resulting in positively density-dependent resource harvest. Mice also made significantly more patch visits, made more out-of-patch foraging bouts (taking seeds to protective cover), and spent more time foraging out of the resource patches in the presence of fire ants. Despite any increased costs or lost time due to taking seeds to protective cover, mice harvested the same number of seeds in the same total time at the same overall harvest rate in the presence and absence of fire ants. The increased costs associated with foraging in the presence of fire ants were compensated for by biasing effort toward rich patches. Mice harvested more seeds, spent more time, and had a disproportionately higher harvest rate in rich patches in the presence of fire ants; there were no differences between use of rich and poor patches in their absence.
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Holtcamp, Wendee Nicole (1995). Patch use under predation hazard: effects of the red imported fire ant on deer mice foraging behavior. Master's thesis, Texas A&M University. Available electronically from