Exploring the mechanisms of iridescence as camouflage

  • Dylan H N Thomas

Student thesis: Master's ThesisMaster of Science by Research (MScR)

Abstract

Iridescence is a taxonomically widespread form of structural colouration that produces striking rainbow-like hues. It has a wide range of hypothesised biological functions, including species recognition, mate choice, thermoregulation, and – rather counter-intuitively – camouflage. Empirical evidence for iridescence as camouflage is relatively recent and, as such, exactly how iridescence provides effective concealment has remained unknown. Here, the functional mechanisms of iridescence as camouflage are explored, with a particular focus on separating the relative contributions of target colour and target gloss. Using field experiments with natural avian predators, the survival of iridescent and non-iridescent beetle-like targets was investigated. Consistent with previous research, iridescent colouration was found to have strong protective benefits. Target colour was found to be the most important factor in enabling this camouflaging effect. Target gloss and the gloss of the leaves on which targets were placed were both found to significantly affect survival, but they were less important in providing effective concealment. The roles of each factor in iridescence as camouflage are discussed, and it is concluded that changeable iridescent colours likely provide camouflage by reducing the signal-to-noise ratio.
Date of Award2 Dec 2021
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorInnes C Cuthill (Supervisor) & Heather M Whitney (Supervisor)

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