Uniform predation risk in nature: common, inconspicuous, and a source of error to predation risk experiments

Abstract

Previous studies indicate that when predation risk is uniform across habitats, foragers concentrate their exploitation in fewer patches. Although uniform predation risk may seem rare in nature, some scenarios might cause it. Testing all scenarios in a single experiment is unfeasible; therefore, we developed a model that points whether concentration of exploitation in specific habitats due to uniform risk requires parameter values similar to what is found in literature. This model was based on Brown's (Behav Ecol Sociobiol 22:37-47, 1988) fitness function but rescaled to multiple habitats and predators, including uniform risk predators. Deriving function's maximum allowed comparisons with giving-up density studies. Results showed that uniform predation risk had a ushaped effect in habitat exploitation, causing a concentration of habitat exploitation at probabilities of survival from 0.2 to 0.8. However, the length of this interval and degree of concentration depended on the value of safety to forager fitness. Heterogeneous, nonuniform, predation risk decreases habitat exploitation where it was higher, therefore suppressing the effect of uniform risk on prey behavior. Time spent in the focal habitat and metabolic costs reduced the detectability of habitat concentration, while total time did not. We also found that uniform risk reduced accuracy of heterogeneous risk measurements. Future studies should aim to control all possible predators, as even the mild ones can induce complex behavior.

High moon brightness and low ambient temperatures affect sloth predation by harpy eagles

“…Leaf abscission presented no effects on predation of sloths. Although we predicted increased probability of arboreal prey detection under leafless conditions in the semi-deciduous forests of central Panama, forest areas dominated by leafless trees and/or woody lianas may be consistently avoided by prey species relying on concealed foraging activity (Menezes, Kotler & Mourão, 2014;Menezes, Mourão & Kotler, 2017). For a sloth, leafless tree crowns offer little if any protective cover and no food resources.…”

“…Conversely, the dry season often induces leaf abscission in trees and woody lianas (Souza, Gandolfi & Rodrigues, 2014), which may limit food availability and shelter to arboreal folivores. The combination of reduced cover and limited food resource availability can enhance predation risk (Menezes, Kotler & Mourão, 2014;Menezes, Mourão & Kotler, 2017). The seasonal variation may modify the range of thermal microhabitats available to a prey species.…”

Among-individual differences in foraging modulate resource exploitation under perceived predation risk

“…Kotler and Brown 1999 ; Dall et al 2000 ). Risk-uniform landscapes have received very little attention, albeit—from a forager’s perspective—they are not uncommon (but see Eccard and Liesenjohann 2008 ; Eccard et al 2008 ; Liesenjohann and Eccard 2008 ; Menezes et al 2014 ). The available studies revealed that under uniform risk foragers may exploit a few patches only, particularly under high risk (Eccard and Liesenjohann 2008 ).…”

Peer Review #2 of "High moon brightness and low ambient temperatures affect sloth predation by harpy eagles (v0.1)"

“…The combination of reduced cover and limited food resource availability can enhance predation risk (Menezes, Kotler & Mourão, 2014;Menezes, Mourão & Kotler, 2017). The seasonal variation may modify the range of thermal microhabitats available to a prey species.…”