Larval long‐toed salamanders incur nonconsumptive effects in the presence of nonnative trout

Erin K Kenison,Andrea R Litt,David S Pilliod,Thomas E Mcmahon

doi:10.1002/ecs2.1258

Abstract

AbstractPredators can influence prey directly through consumption or indirectly through nonconsumptive effects (NCEs) by altering prey behavior, morphology, and life history. We investigated whether predator‐avoidance behaviors by larval long‐toed salamanders (Ambystoma macrodactylum) in lakes with nonnative trout result in NCEs on morphology and development. Field studies in lakes with and without trout were corroborated by experimental enclosures, where prey were exposed only to visual and chemical cues of predators. We found that salamanders in lakes with trout were consistently smaller than in lakes without trout: 38% lower weight, 24% shorter body length, and 29% shorter tail length. Similarly, salamanders in protective enclosures grew 2.9 times slower when exposed to visual and olfactory trout cues than when no trout cues were present. Salamanders in trout‐free lakes and enclosures were 22.7 times and 1.48 times, respectively, more likely to metamorphose during the summer season than those exposed to trout in lakes and/or their cues. Observed changes in larval growth rate and development likely resulted from a facultative response to predator‐avoidance behavior and demonstrate NCEs occurred even when predation risk was only perceived. Reduced body size and growth, as well as delayed metamorphosis, could have ecological consequences for salamander populations existing with fish if those effects carry‐over into lower recruitment, survival, and fecundity.

Highlights

To avoid predation, prey use tactile, visual, or chemical cues to detect predators and respond with appropriate defense tactics (Kats et al 1988, Stauffer and Semlitsch 1993, Lima 1998)
Despite some differences in physical attributes of lakes, we considered them to be comparable given that densities of salamanders were similar on the basis of catch per unit effort in lakes with and without trout
Salamander larvae weighed 38% less, were 24% shorter in total length (6– 43%, t12 = −2.60, P = 0.02), and had 29% shorter tails (7–50%, t12 = −3.08, P = 0.01, Fig. 2A). These differences were present at the beginning of the summer, did not differ between years, and the magnitude of difference did not change over the summer seasons

Summary

Introduction

Prey use tactile, visual, or chemical cues to detect predators and respond with appropriate defense tactics (Kats et al 1988, Stauffer and Semlitsch 1993, Lima 1998). Other defenses are facultative and induced by the presence of predators, resulting in changes in behavior, morphology, and life history of prey (Lima 1998, Benard 2004). Such defensive strategies may reduce the probability of predation, they often come with a cost (Lima 1998). Individuals that reduce activity are less likely to be detected and captured by predators, but v www.esajournals.org

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