What color is your carnivore?

The splotches, rings, and stripes on a carnivore's face reveal the fingerprints of evolutionary forces in its past, argues Alessia Ortolani of the University of California, Davis. She is trying to crack me code.

Ortolani pieced together a huge family tree showing the evolutionary relationships of 200 terrestrial carnivores. Its twigs bristle with dogs, cats, hyenas, and weasels, as well as lesser-known species such as somewhat catlike African genets. Then, Ortolani focused on particular facial markings, looking for patterns in the histories of the animals that bear them.

In her analysis, white markings around the eyes, like the crescents under a tiger's eyes, often appear in lineages of nocturnal predators that prowled dense forests. The white marks could have aided communication among creatures sorting out friends and foes by their facial expressions in the gloom, Ortolani speculates.

In lineages of grassland species, like African wild dogs, that roam open spaces, Ortolani found many dark muzzles. In daylight, these features stand out, suggesting they might serve as a conspicuous signal for diurnal animals.