Why don't all poison dart frogs look the same?
(Image credit: Flickr user William Wan)
Nothing says "STAY AWAY!" to a predator like a tasty-looking creature that's a little too flashy. Bright colors and crazy patterns are nature's skull and crossbones, a warning to the carnivorous to look elsewhere for meals. Toxic animals usually have uniform markings: Each member of a species looks the same. Monarch butterflies bear the same patterns; puffer fish all puff up in the same way. But there's one animal that ignores this advice completely: the poison dart frog. These deadly amphibians have developed endless combinations of shades and markings, making it a challenge for hungry birds and snakes to keep track of their patterns. If the idea of being visibly toxic is to be as obvious as possible, why would a single species of frog maintain such an extensive wardrobe? That's the question that had Mathieu Chouteau sweating in the Peruvian Amazon as fastened 1,800 clay frogs to rainforest leaves.
(Image credit: Flickr user MoleSon²)
Back in 2009, Chouteau, a biologist from the University of Montreal, became obsessed with this evolutionary puzzle. "For the longest time, I've been fascinated by the phenomenon of local adaptation," he says. But because the varieties of poison dart frog patterns are so many and, more importantly, occur so geographically close to one another, they struck Chouteau as particularly odd. He wondered whether different types of local predators were somehow responsible for the variations.