An Invasive Shrub Causes Risk-Prone Behavior in a Larval Amphibian (American Toad Tadpoles) - via Herp Digest

• Behavioral Ecology/Volume 25, Issue 2/Pp. 300-30

1. Caleb R. Hickman^a,^b and
2. James I. Watling^c

- Author Affiliations

1. ^a Department of Zoology, University of Wisconsin, Madison, WI 53706, USA, 
2. ^b Eastern Band of Cherokee Indians, Fisheries and Wildlife Management, PO Box 1747, Cherokee, NC 28719, USA, and 
3. ^c University of Florida, Ft Lauderdale Research and Education Center, 3205 College Avenue, Ft Lauderdale, FL 33314, USA 
4. Address correspondence to C.R. Hickman. E-mail: calebhickman@gmail.com.

Abstract

Invasive plants influence the quality of habitats they invade by transforming the physical structure of forests and changing the chemical composition of aquatic environments. Prey may accept higher predation risk as they manage lower quality environments caused by invasive plants. Leachates from invasive Amur honeysuckle cause American toad tadpoles to swim to the surface, which may alter typical antipredator freezing behaviors and expose tadpoles to detection by predators. We use a factorial laboratory experiment to condition individual tadpoles to leaf leachates made from honeysuckle, native trees, or a water control followed by exposure to experimental arenas with one of 3 chemical cues (2 predator species or control water). Toad tadpoles increased their latency to move (freezing) and had a lower total movement to predator cues. In contrast, latency to move was faster in response to honeysuckle leachates, but leaf leachates had no influence on total movement activity. Tadpoles did not change surfacing frequency to predator cues but increased surfacing to honeysuckle leachate. The combined effect of predator cue and leachate treatment had no influence on behaviors. Although honeysuckle leachate is stressful to toad tadpoles, increased surfacing does not preclude the exhibition of typical antipredator behaviors (decreased movement). However, honeysuckle induced a risk-prone response of increased surfacing, even in the presence of predator cues. As tadpoles endure physiological costs from honeysuckle, they may suffer elevated exposure to detection by predators. Our work provides insight into how invasive plants may have indirect effects on native communities by altering animal behaviors.