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

Abstract

Predators 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.

Evaluating adaptive, carry‐over, and plastic antipredator responses across a temporal gradient in Pacific chorus frogs

“…Predator‐induced phenotypes can induce fitness costs in later life stages (Kenison et al. ). In our study, embryonic conditioning to predation risk produced shorter, less developed tadpoles.…”

Few Impacts of Introduced Cutthroat Trout (Oncorhynchus clarki) on Aquatic Stages of Boreal Toads (Anaxyrus boreas boreas)

“…To date, most trout-amphibian interaction studies report a reduction in amphibian distribution and abundance (e.g., Bradford et al, 1998;Knapp, 2005;Welsh et al, 2006). Few studies have experimentally investigated the potential direct or indirect mechanisms by which trout impact different amphibian life stages (but see Tyler et al, 1998;Kiesecker et al, 2001;Vredenburg, 2004;Pearson and Goater, 2009;Kenison et al, 2016). Knowledge of the mechanisms by which trout negatively affect amphibian life stages may assist managers tasked with conserving declining populations.…”