Researchers break the animal kingdom's colour code

April 16, 2009

Charles Darwin was fascinated by the colours of animals - he once wrote to his colleague Alfred Russell Wallace asking why certain animals were "so
beautifully and artistically coloured".

It is a question that has intrigued biologists ever since. Now research spearheaded at the University of York (in collaboration with researchers from the University of Glasgow, and Carleton University in Canada) has used computer models to trace the evolution of this extravagant colouring.

Researchers in the York Centre for Complex Systems Analysis (YCCSA) sought to explain why most animals that have an anti-predatory defence, such as a
sting or poison, tend to be brightly coloured.

Mimicry is common in nature. Defenceless species frequently evolve to look like a nasty species, so that potential predators cannot distinguish between
the two -- a good meal or an unpleasant experience.

Such mimicry is good for the defenceless species which predators can mistake for a daunting adversary, but is bad for nasty species which might be
mistaken as a good meal.

The YCSSA research, published in Evolution, suggests that nasty prey may have evolved bright colours to avoid this kind of mimicry. Bright colours are harder for defenceless prey to mimic because they have a survival cost of increased detectability by predators. There are also many ways to look distinctive when brightly coloured, but limited scope for doing so when camouflaged, because camouflage needs to blend in with the background.

Lead researcher Dr Dan Franks, of YCCSA, said: "Our computer models show that this way of looking at the evolution of bright colours explains why in
nature we generally find that the nastier the prey species (e.g. the more poisonous) the brighter the animal.

"The nastier the animal, the more it can 'afford' a bright and distinctive livery to copyright its appearance. It's similar to the way that big
companies closely guard their appearance in an attempt to build clear brand recognition."

More information: D.W. Franks & G.D. Ruxton & T.N. Sherratt (2009) Warning signals evolve to disengage Batesian mimics, Evolution , 63(1): 256-267 http://www3.interscience.wiley.com/journal/117958524/home

Provided by University of York