The eyes of the spectacled bear sit in disks of black fur on a stark white face. The African civet sports a necklace of dark and light bands. And hundreds of other mammalian predators have their own unique facial and chest markings that scientists have struggled to explain. Now, a new study is helping unravel some of the mystery.
Prey animals develop spots and stripes on their bodies to blend in with their environments and avoid detection; think the zebra. Many predators do, too, but even those without body camouflage still sport patterns on their face and chest, suggesting the markings aren’t all about blending in.
To figure out the purpose of these patterns, Tim Caro, a biologist at the University of California, Davis, and colleagues collected photographs of 164 terrestrial predators from six families of predators—canids, felids, ursids (bears), mustelids (which include weasels, otters, and badgers), viverrids (which include civets, binturongs, and other catlike animals), and herpestids (mongooses and meerkats). They used several photos of each species to account for various lighting conditions, then analyzed how many colors and shades were present, as well as how those colors contrasted with one another. A face or chest pattern with several highly contrasted color shades—like the masked palm civet (Paguma larvata)—was given a high complexity score, whereas animals with fairly uniform faces and chests had lower scores.
The researchers then looked at how those scores matched up with those animals’ behavioral traits. In canids, they found that species that sport complex chest patterns—like the Ethiopian wolf (Canis simensis), with a striking white bow tie across its chest, contrasting a tawny coat—tend to be more social, hunting and spending more time in large groups. In these animals, the markings might allow individuals to recognize one another, the researchers report this month in Behavioral Ecology and Sociobiology.
In viverrids like the African civet (Civettictis civetta), highly striped and color-flecked faces belonged to species that were more likely to fight back against other predators, indicating the markings might serve as a warning. The patterns might also help camouflage them as they stalk their prey head on, Caro says, as the marks might prevent their prey from making out the predators’ facial features.
In bears, species whose range overlaps with other bears’ tend to have more complex faces. This may help them identify their own species and avoid outside mating. But with only eight species of bears, Caro says there aren’t enough data to know for sure.
In mustelids like the Indonesian stink badger (Mydaus javanensis) and the African skunk (Ictonyx striatus), animals with more complex facial shading were more likely to be able to spray a noxious fluid jet from their anal glands, warning predators to keep their distance. Here, facial shading likely evolved as a warning signal to predators: You may be able to eat me, but you’ll regret it.
And finally, in felids, the data were inconclusive: None of the facial and chest patterns matched up significantly with any of the life traits the researched looked at, though it’s possible they just haven’t identified the right variables yet.
“What this study shows is that there are different evolutionary drivers for coloration in this group,” Caro says.
The conclusion is convincing, says Geoffrey Hill, a biologist who studies animal coloration at Auburn University in Alabama. But he adds that future studies should take into account additional variables such as whether the animals are active at day or night and what the species’s habitat is like.
Caro agrees, noting that his work is building toward understanding coloration in mammals with evolutionary histories closer to our own. Many apes and monkeys also have complex coloration patterns across their faces and chests, and researchers aren’t sure why they evolved them. “The holy grail in coloration is primates,” he says. “We’re just beginning to lay the groundwork that will get us there.”
Read the original article in Science Magazine.