Habitat disturbance alters color contrast and the detectability of cryptic and aposematic frogs

• Published in: Behavioral ecology Vol. 32; no. 5; pp. 814 - 825
• Main Authors: Barnett, James B, Varela, Brandon J, Jennings, Ben J, Lesbarrères, David, Pruitt, Jonathan N, Green, David M
• Format: Journal Article
• Language: English
• Published: UK Oxford University Press 01-09-2021
• Subjects: human disturbance; aposematism; habitat change; camouflage
• ISSN: 1045-2249; 1465-7279
• DOI: 10.1093/beheco/arab032

Abstract
Animals use color both to conceal and signal their presence, with patterns that match the background, disrupt shape recognition, or highlight features important for communication. The forms that these color patterns take are responses to the visual systems that observe them and the environments within which they are viewed. Increasingly, however, these environments are being affected by human activity. We studied how pattern characteristics and habitat change may affect the detectability of three frog color patterns from the Bocas del Toro archipelago in Panama: Beige-Striped Brown Allobates talamancae and two spotted morphs of Oophaga pumilio, Black-Spotted Green and Black-Spotted Red. To assess detectability, we used visual modeling of conspecifics and potential predators, along with a computer-based detection experiment with human participants. Although we found no evidence for disruptive camouflage, we did find clear evidence that A. talamancae stripes are inherently more cryptic than O. pumilio spots regardless of color. We found no evidence that color pattern polytypism in O. pumilio is related to differences in the forest floor between natural sites. We did, however, find strong evidence that human disturbance affects the visual environment and modifies absolute and rank order frog detectability. Human-induced environmental change reduces the effectiveness of camouflage in A. talamancae, reduces detectability of Black-Spotted Green O. pumilio, and increases chromatic contrast, but not detectability, in Black-Spotted Red O. pumilio. Insofar as predators may learn about prey defenses and make foraging decisions based on relative prey availability and suitability, such changes may have wider implications for predator–prey dynamics.
Color patterns are used by animals to conceal, or signal, their presence, but the distinction between camouflage and conspicuousness is often dependent on the background. We found that the absolute, and rank-order, detectability of leaf litter frogs at a site of increased human activity differed from that at an adjacent undisturbed site. These changes to detectability may affect the efficacy of individual defensive strategies but may also influence how predators forage on multiple prey types.