American Society of Naturalists

Barney Luttbeg, Maud C. O. Ferrari, Daniel T. Blumstein, and Douglas P. Chivers (Apr 2020)

Prey fitness increased by safety cues (precise information at low risk levels) over danger cues (precise at high risk)

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Prey fear of predators shaping ecological communities has become a widespread perspective for ecologists. The primary story has been that prey forage and do other kinds of risky behaviors until they receive a cue that indicates that a predator is currently nearby or about to attack. This view has emphasized how risk and fear shapes the behaviors of prey and ecological dynamics. But what if there are cues that are more effective at indicating low levels of predation risk? Would prey benefit more from these safety cues than from danger cues that are effective at indicating high levels of predation risk?

Scientists from Oklahoma State University, the University of Saskatchewan, and the University of California at Los Angeles answer these questions using computer models. They find that when prey pay more attention to safety cues than to the danger cues they are more successful at avoiding predators and finding food. This happens because safety cues provide prey with precise information about low predation risk levels where they should should be varying how intensely they forage. Danger cues, however, often provide precise information about high levels of predation risk where they should be hiding from predators. These results may begin a shift from only thinking about how fear shapes ecology to also thinking about how indications of safety shape prey behavior, physiology, and ecological dynamics.

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Abstract

The ability of prey to assess predation risk is fundamental to their success. It is routinely assumed predator cues do not vary in reliability across levels of predation risk. We propose that cues can differ in how precisely they indicate different levels of predation risk. What we call danger cues precisely indicate high risk levels, while safety cues precisely indicate low risk levels. Using optimality modeling, we find that prey fitness is increased when prey pay more attention to safety cues than danger cues. This fitness advantage is greater when prey need to protect assets, predators are more dangerous, or predation risk increases at an accelerating rate with prey foraging efforts. Each of these conditions lead to prey foraging less when estimated predation risk is higher. Danger cues have less value than safety cues because they give precise information about risk when it is high, but prey behavior varies little when risk is high. Safety cues give precise information about levels of risk where prey behavior varies. These results highlight how our fascination with predators may have biased the way we study predator-prey interactions and focused too exclusively on cues that clearly indicate the presence of predator rather than cues that clearly indicate their absence.