Behaviour 2019
Foraging with a Handicap
Abdel H. Halloway1, Joel S. Brown2,3, Robert D. Holt4, Burt P. Kotler5. 1University of Illinois, Urbana-Champaign, Urbana, Illinois, United States; 2Moffitt Cancer Center, Tampa, Florida, United States; 3University of Illinois at Chicago, Chicago, Illinois, United States; 4University of Florida, Gainsville, Florida, United States; 5Ben Gurion University of the Negev, Beersheba, , Israel

Handicaps like disease can reduce foraging benefits while increasing predation risk and alter the adaptive foraging strategies of handicapped individuals.  We use a three-trophic level predator-prey-resource model to analyse how a handicap changes foraging in the prey. Handicaps affect model parameters that determine optimal vigilance, giving-up densities (GUDs), and quitting harvest rates (QHRs). We compared our model results to experiments in which gerbils, foraging for seeds and attacked by barn owls, were infected with either ectoparasites (fleas) or endoparasites (bacteria).  These parasites have distinct effects.  Both show increased GUD and QHR with increased predation, consistent with theory. Bacteria-infected gerbils increased vigilance and time foraging, matching our theory. However, flea-infected gerbils changed time spent foraging without changing vigilance, inconsistent with our theory.  Overall, theory provided a good but not perfect match to our empirical results.  We suggest that the discrepancy may reflect a factor we did not have in our model – the time allocation of prey to attention.