A new study carried out by researchers at the University of Bristol, tries to answer the question everyone has asked themselves at least once: 'Why do leopards have spots and tigers have stripes?' They studied 35 species of wild cats and analysed their fur markings, to understand what makes them have such different patterns on their fur.

The researchers photographed different details in the looks of the cats and integrated them into a mathematical model of pattern development.

The conclusion was that the animals that lived in the trees, in dense habitats and were active at low levels of light, have the most chances to be pattern. These very complex and irregular models on their fur have probably evolved to help the cats have a good camouflage.

This link between environment and fur patterns is quite strong but after looking at the evolutionary history, we can see that these patterns can evolve but also disappear quite fast. It also gives an explanation to why black leopards are common but black cheetahs are unknown - leopards live in several habitats and also behave differently. Several environments allow one species to develop original colours and patterns and to make them permanent in a population.

The explanation linking leopards' patterns with environment is plausible but it also highlighted some exceptions: some cheetahs have spots even though they live in open spaces, while the bay cat and the flat-headed cat, who prefer closed habitats have plain coats. Another intriguing thing is that out of the 35 species, only one cat has vertically elongated patterns, that had nothing to do with grasslands: the tiger. On the other hand, tigers seem to camouflage really well so why don't other animals have vertical stripes too?

There are still questions to be answered, but this method confirms Rudyard Kipling's explanation of leopard's spots and the environment "full of trees and bushes and stripy, speckly, patchy-blatchy shadows".

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