Experimental studies of iridescence as camouflage

Abstract

Iridescence is a form of structural colouration that describes how surfaces change colour dependent upon angle of view. It is taxonomically widespread and theorised to have numerous biological functions including mate choice, species recognition, aposematism, thermoregulation, and potentially camouflage. Recent experimental evidence has demonstrated that artificial iridescent beetle targets are less detectable than similarly-coloured, non-iridescent beetle targets in both avian and human detection studies in the field. However, the mechanisms are still unknown. This thesis therefore aims to explore the mechanisms by which iridescence can function as camouflage by exploring how detectable different colours of iridescence, beyond the natural colours of many beetle wings, are to avian subjects and humans, in both field and lab studies. The results show that when the salience of targets dropped at certain viewing angles, iridescence can result in crypsis through background matching. However, colour changeability, characteristic of iridescent surfaces, is itself not sufficient for camouflage. It is therefore concluded that camouflage is unlikely to be the primary function of iridescence in many animals, however the costs of this structural colouration can be reduced if background matching, at certain angles of view, is present.

Date of Award	23 Jan 2024
Original language	English
Awarding Institution	University of Bristol
Supervisor	Innes C Cuthill (Supervisor)