Aposematic signals in North American black widows are more conspicuous to predators than to prey


Journal Article

© 2016 The Author. The iconic red hourglass of the black widow spiders (genus Latrodectus) is traditionally considered an aposematic signal, yet experimental evidence is lacking. Here, we present data that suggest that black widow coloration may have evolved to be an aposematic signal that is more conspicuous to their vertebrate predators than to their insect prey. In choice experiments with wild birds, we found that the red-and-black coloration deters potential predators: Wild birds were ~3 times less likely to attack a black widow model with an hourglass than one without. Using visual-system appropriate models, we also found that a black widow's red-and-black color combo is more apparent to a typical bird than a typical insect. Additionally, an ancestral reconstruction reveals that red dorsal coloration is ancestral in black widows and that at some point some North American widows lost their red dorsal coloration. Behaviorally, differences in red dorsal coloration between 2 North American species are accompanied by differences in microhabitat that affects how often a bird will view a black widow's dorsal region. All observations are consistent with a cost-benefit trade-off of being more conspicuous to predators than to prey. We suggest that limiting detection by prey may help explain why red and black aposematic signals occur frequently in nature.

Full Text

Duke Authors

Cited Authors

  • Brandley, N; Johnson, M; Johnsen, S

Published Date

  • January 1, 2016

Published In

Volume / Issue

  • 27 / 4

Start / End Page

  • 1104 - 1112

Electronic International Standard Serial Number (EISSN)

  • 1465-7279

International Standard Serial Number (ISSN)

  • 1045-2249

Digital Object Identifier (DOI)

  • 10.1093/beheco/arw014

Citation Source

  • Scopus