Edited by Clive Cookson
Published: October 30 2010 00:33 | Last updated: October 30 2010 00:33
|Living in a variety of environments, leopards can develop atypical spot colours and patterns|
Rudyard Kipling had more or less the right idea. In the “How the Leopard Got His Spots” story from the Just So collection, the Ethiopian endowed his feline friend with spots as camouflage for life in the trees. “You can lie out on a leafy branch and look like sunshine sifting through the leaves; and you can lie right across the centre of a path and look like nothing in particular,” the Ethiopian told the Leopard. “Think of that and purr!”
Scientists at Bristol University analysed the markings of 35 wild cat species to understand better what drives the evolution of so many beautiful and intriguing patterns. They captured detailed differences in the visual appearance of the cats by linking them to a mathematical model of pattern development.
Broadly they confirmed that coat markings help the animals to melt into their surroundings. All cats benefit from camouflage as predators, helping them to stalk their prey until they are close enough to catch it. And small cats also benefit from protection from predation by big carnivores.
Cats such as leopards – which live in dense habitats, among trees and are active at low light levels – are the most likely to be patterned, especially with irregular or complex shapes. Species that live in open grassland, such as lions, tend to have plainer coats.
The research also explains why black leopards are common but black cheetahs unknown. Unlike cheetahs, leopards live in a wide range of habitats and have varied behavioural patterns.
Having several environmental niches that different individuals of the species can exploit allows atypical colours and patterns to become stable within a population.
Although a clear link between environment and patterning was established, the study highlighted some anomalies that remain unexplained. For example, a number of cats, such as the bay cat and the flat-headed cat, have plain coats despite a preference for closed environments.
The research (published in Proceedings of the Royal Society B) also highlighted just how rare vertical stripes are.
Only tigers always have vertically elongated patterns. Since tigers seem to be well camouflaged, this raises the question of why vertical stripes are not more common in cats and other mammals.
The researchers ruled out any significant role for coat patterns either as sexual attractants or social signalling systems.
And analysis of the evolutionary history of coat patterns shows they can arise and disappear relatively quickly.
“The method we have developed offers insights into cat patterning at many levels of explanation and we are now applying it to other groups of animals,” says Will Allen, who led the research.