Risky prey behavior evolves in risky habitats

Abstract

Longstanding theory in behavioral ecology predicts that prey should evolve decreased foraging rates under high predation threat. However, an alternative perspective suggests that growth into a size refuge from gape-limited predation and the future benefits of large size can outweigh the initial survival costs of intense foraging. Here, I evaluate the relative contributions of selection from a gape-limited predator (Ambystoma opacum) and spatial location to explanations of variation in foraging, growth, and survival in 10 populations of salamander larvae (Ambystoma maculatum). Salamander larvae from populations naturally exposed to intense A. opacum predation risk foraged more actively under common garden conditions. Higher foraging rates were associated with low survival in populations exposed to freeranging A. opacum larvae. Results demonstrate that risky foraging activity can evolve in high predation-risk habitats when the dominant predators are gape-limited. This finding invites the further exploration of diverse patterns of prey foraging behavior that depends on natural variation in predator size-selectivity. In particular, prey should adopt riskier behaviors under predation threat than expected under existing risk allocation models if foraging effort directly reduces the duration of risk by growth into a size refuge. Moreover, evidence from this study suggests that foraging has evolved over microgeographic scales despite substantial modification by regional gene flow. This interaction between local selection and spatial location suggests a joint role for adaptation and maladaptation in shaping species interactions across natural landscapes, which is a finding with implications for dynamics at the population, community, and metacommunity levels. contemporary evolution ͉ gene flow ͉ growth-foraging tradeoffs ͉ predator-prey interactions ͉ prey size refuge

Evolution mediates the effects of apex predation on aquatic food webs

“…Marbled salamanders impose strong selection on spotted salamander growth and foraging behaviours [25,26]. This selection is based in part on the marbled Table 1.…”

“…(*p , 0.05; **p , 0.10; ***p . salamander's strong gape-limitation that allows spotted salamander larvae to grow into a size refuge [26,29]. Other predators are not gape-limited on spotted salamanders, such as the diving beetle Dytiscus verticalis, and produce opposing selection on foraging traits [25].…”

“…Most other predator species select for reduced foraging in spotted salamanders because rapid foraging produces higher instantaneous predation risk for gape-unconstrained and visually oriented predators [30]. In response to this antagonistic selection, research suggests that spotted salamander populations that co-occur with marbled salamanders forage more intensely than those in ponds dominated by other predator species [26].…”

Evolutionary ecology of inducible morphological plasticity in predator–prey interaction: toward the practical links with population ecology

“…Such additive responses are frequently observed in the morphological and behavioral defenses of animal prey when confronted with predation risk (DeWitt et al 1999;Rundle and Brönmark 2001;Van Buskirk 2002; Laurila 2007 see also Urban 2007). For example, many species of amphibian larvae increase their tail depth to reduce their vulnerability to predators because an enlarged tail may enhance swimming performance (Dayton et al 2005) or attract the predator to a less vital part of their body such as the head (Van Buskirk et al 2003).…”

Increased juvenile predation is not associated with evolved differences in adult brain size in Trinidadian killifish (Rivulus hartii)

“…It is well known that the trajectory of evolution for many classes of traits depends upon the age and/or size classes that experience predator‐induced mortality (Brown, 2003; Charlesworth, 1980; Jonsson & Jonsson, 2014; Sih, Kats, & Maurer, 2003; Urban, 2007). For example, increased rates of juvenile predation are associated with the evolution of delayed maturation and decreased reproductive effort (Reznick & Endler, 1982; Sparkes, 1996a,b; Walsh & Reznick, 2009; Wellborn, 1994).…”