Beetle iridescence a deceptive form of warning coloration

Date:
May 3, 2022
Source:
University of Bristol
Summary:
A new study published today in Animal Behaviour shows for the first
time that brilliant iridescence and gloss found in some animals
can have a protective function by working as a form of deceptive
warning coloration, and that it is the key feature of iridescence,
its changing colors, that is important for this effect.



FULL STORY ==========================================================================
A new study published today in Animal Behaviour shows for the first time
that brilliant iridescence and gloss found in some animals can have a protective function by working as a form of deceptive warning colouration,
and that it is the key feature of iridescence, its changing colours,
that is important for this effect.


==========================================================================
This striking form of structural coloration in which the hue and intensity
of colours will vary depending on the angle of view, has also evolved independently in everything from birds such as magpies and starlings, to
many insects such as rose chafers, rosemary beetles and in the demoiselle.

By looking at its biological functions, a team of researchers at Bristol University's CamoLab investigated why this vivid metallic coloration
has evolved so may times in the animal kingdom, and what makes this
striking form of animal coloration such a successful anti-predator
strategy. The team had previously discovered that iridescence can act as
a highly efficient form of camouflage, but whether such striking forms of structural coloration could also protect prey post-detection, and if so,
what optical properties were important for this effect, remained unknown
until now.

Lead author Dr. Karin Kjernsmo of the University of Bristol's School
of Biological Sciences said: "One of the challenges when studying the
functions of such highly reflective structural colouration has been to
separate the effects of the changeability of colours, the hallmark of iridescence, from the effects of simply having multiple colours at the
same time, and also to separate the effects of gloss from the effects
of iridescence." They tested if and how iridescence could provide a
survival benefit to prey post-detection by presenting both iridescent
and non-iridescent, as well as glossy and matte versions of the two,
to birds that had no previous experience with such prey, and then looked
at the birds' willingness to attack the prey.

They found that iridescence significantly reduced the attack-willingness
of the birds, and that gloss also had 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 added.

The study was funded by the Biotechnology & Biological Sciences Research Council (BBSRC).


========================================================================== Story Source: Materials provided by University_of_Bristol. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Karin Kjernsmo, Anna M. Lim, Rox Middleton, Joanna R. Hall, Leah M.

Costello, Heather M. Whitney, Nicholas E. Scott-Samuel, Innes
C. Cuthill.

Beetle iridescence induces an avoidance response in nai"ve
avian predators. Animal Behaviour, 2022; 188: 45 DOI: 10.1016/
j.anbehav.2022.04.005 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/05/220503141337.htm

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