Date of Award

Spring 2017

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Dr. Christopher Sheil

Abstract

Crypsis and aposematism are common antipredator strategies that have evolved as defensive mechanisms to prevent predation. Prey that employ these defensive strategies also exhibit antipredator behaviors meant to avoid or deter predation. These behaviors include: (1) escape or immobility in the presence of an immediate predator or (2) exhibiting bold behavior by accepting the risk of potential predation in a novel environment in exchange for the benefits of foraging and mating opportunities. In this study, the escape and bold behaviors of cryptic members of Craugastor and the aposematic dendrobatid Dendrobates auratus were tested to compare these alternative antipredator strategies. Craugastor behaved more cryptically and was less bold than D. auratus in response to simulated predators and when emerging from a cover object. Further, a human and bird model were used as simulated predators to compare the escape behaviors exhibited by Craugastor and D. auratus in response to each. The results of this study support previous findings that cryptic anurans commonly rely on immobility to maximize camouflage, whereas aposematic anurans exhibit movement that enhance their warning signals. Also, movements exhibited by D. auratus were distinctive based on the identity of the approaching predator, suggesting that predator type is important when studying the escape behavior of an aposematic species. Furthermore, although crypsis and aposematism are thought to be alternative strategies, a continuum ranging from cryptic to aposematic may exist within aposematic species. The color/pattern and alkaloid chemical defense of individual D. auratus were measured and compared to their antipredator behavior to establish a potential spectrum of antipredator strategies. Two populations of D. auratus were found to exhibit alternative antipredator strategies – the Atlantic population was more bold, conspicuous, and chemically defended than the Pacific population. The two populations of D. auratus support the possibility that crypsis and aposematism are not mutually exclusive. Instead, populations of D. auratus, in response to unique selective pressures, can utilize a combination of antipredator strategies including morphology and behavior.

Download

Included in

Biology Commons

Share

COinS