Brilliant iridescence can conceal as well as attract

Brilliant iridescence can conceal as well as attract - University of Bristol

A new study shows for the first time that the striking iridescent colours seen in some animals increase their chances of survival against predators by acting as a means of camouflage. Rather than reveal it seems these dynamically changing shades are used to conceal, according to the University of Bristol study published today [23 January] in Current Biology.

Until now, it was assumed that the iridescent colours seen in nature have two main purposes: they can help animals find mates, or act as a warning to predators that a prey item may be poisonous.

Researchers at Bristol’s Camo Lab wanted to find out why this vivid metallic coloration has evolved in so many different species of animals by investigating its biological function. They chose to test this theory on the vividly coloured jewel beetle (Sternocera aequisignata) because both sexes of this species are iridescent which makes sexual signalling somewhat less likely as a function of the colour.

They tested the idea of iridescence-as-camouflage by placing iridescent and non-iridescent beetle models on leaves in the forest and noted their survival against attacks by wild birds. They found that the models with biological iridescence, survived best against birds, providing evidence that iridescence can increase prey survival and that these bright metallic colours could have evolved in beetles to confuse birds – their primary predator.

Dr Karin Kjernsmo, the study’s lead author at the University of Bristol School of Biological Sciences, said: “Iridescent colours are most likely familiar to you from everyday objects such as soap bubbles and CDs, but this striking form of structural colour is also very common in nature. Iridescence has evolved independently in everything from jewel-like insects to shimmering birds and can even be spotted in your garden in insects such as Rose Chafers and Rosemary beetles.

Read: Iridescence as Camouflage by Karin Kjernsmo, Heather M. Whitney, Nicholas E. Scott-Samuel, Joanna R. Hall, Henry Knowles, Laszlo Talas and Innes C. Cuthill in Current Biology.