Iridescence and gloss are usually associated with display, but can they also defend? In new research, scientists at the University of Bristol have tested naïve birds’ willingness to attack glossy and iridescent prey.
Kjernsmo et al. show that brilliant iridescence and gloss found in some animals can have a protective function by working as a form of deceptive warning coloration. Image credit: Domianick.
Iridescence is a striking form of structural coloration in which hue and intensity vary with the angle of view or illumination.
It has recently been found that iridescence can act as a highly effective form of camouflage.
However, little is known about whether iridescence can confer a survival benefit to prey postdetection and, if so, which optical properties of iridescent prey are important for this putative protective function.
To investigate this, and to isolate the effects of gloss and iridescence, University of Bristol’s Dr. Karin Kjernsmo and colleagues measured the attack willingness of naïve chicks of the domestic fowl (Gallus gallus domesticus) presented with real and artificial jewel beetle, Sternocera aequisignata, wing cases, all of which were conspicuous on the background against which they were displayed.
“One of the challenges when studying the functions of such highly reflective structural coloration has been to separate the effects of the changeability of colors, the hallmark of iridescence, from the effects of simply having multiple colors at the same time, and also to separate the effects of gloss from the effects of iridescence,” Dr. Kjernsmo said.
The researchers found that iridescence provides initial protection against avian predation by significantly reducing the willingness to attack.
Importantly, they found that the main factor explaining this aversion is iridescence, not multiple colors per se, with surface gloss also having an independent effect.
“Here we have, for the first time, effectively managed to test for each of these two effects on their own, and shown that both iridescence and gloss can protect prey even post-detection, providing yet another adaptive explanation for the evolution and widespread existence of iridescence,” Dr. Kjernsmo said.
The results were published in the journal Animal Behaviour.
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Karin Kjernsmo et al. 2022. Beetle iridescence induces an avoidance response in naïve avian predators. Animal Behaviour 188: 45-50; doi: 10.1016/j.anbehav.2022.04.005
Source link: https://www.sci.news/biology/beetle-iridescence-10774.html
