How do Allenby’s gerbils titrate risk and reward in response to different predators?

• Published in: Behavioral ecology and sociobiology 2020, Vol.74 (1), p.1-10, Article 6
• Main Authors: Makin, Douglas F., Kotler, Burt P.
• Format: Article
• Language: English
• Subjects: Animal behavior; Animal Ecology; Animal populations; Animals; Behavioral Sciences; Biomedical and Life Sciences; Experiments; Food; Food availability; Food safety; Forage; Foraging behavior; Habitats; Hunting; Life Sciences; Microhabitats; ORIGINAL ARTICLE; Predation; Predators; Prey; Reinforcement; Resource availability; Risk; Risk assessment; Safety; Skewed distributions; Small mammals; Titration; Tradeoffs; Zoology
• ISSN: 0340-5443; 1432-0762
• DOI: 10.1007/s00265-019-2785-6

In heterogenous environments, predation risk from multiple predators and the availability of resources fluctuate both spatially and temporally. The various predators may include both aerial and terrestrial species that can facilitate each other and present qualitatively different risks to prey. Animals therefore forage across a complex landscape of fear, with areas of risks and relative safety where resources are generally asymmetrically distributed. Therefore, a trade-off exists between remaining safe and locating food. Animals make foraging decisions regarding where, when and for how long to forage by titrating marginal costs and benefits of foraging within and the marginal value of foraging across depletable resource patches. We conducted a series of titration experiments to determine how Allenby’s gerbils (Gerbillus andersoni allenbyi) titrated food and safety when presented with predation risk from owls, vipers and the joint risk from both predators. We manipulated bush and open microhabitats by increasing food availability in the riskier patches. In response to the different levels of enrichment, gerbils titrated food and safety. Riskier open microhabitats needed to be four times as rich in food as bush patches to be of equal value when subjected to predation from owls and the joint risk from owls and vipers. In response to vipers alone, riskier bush patches needed to be 2–4 times as rich in food as safer open patches for the marginal value of foraging to equalize across microhabitats. Overall, predation risk from owls and the joint risk from owls and vipers resulted in the greatest foraging costs for gerbils in risky microhabitats. Thus, the combined overall risk from multiple predator species was equivalent to the risk presented by the gerbils’ most dangerous predator (owls alone).