This Poisonous Frogs' Bright Colors Weirdly Help Camouflage It

A dyeing poison frog showing off its bright colors. Photo by Bernard DUPONT The conspicuous colors of poison frogs are presumed to be a warning. Indeed, vibrant patterns so often signal toxicity that biologists even have a special term for them: aposematic coloration. But, weird as it might sound, new research suggests that radiant skin patterns might help these frogs stay hidden, too. Poison frogs are armed with some of the planet's most potent toxins. The most deadly is the golden poison frog (Phyllobates terribilis)—one frog's worth of toxin is roughly enough to kill 10,000 mice or about 10 people, though estimates vary. It makes sense for it and other frogs to let potential predators know that eating them is a bad idea, and most do seem to advertise their toxic nature through bright, colorful patterns. The dyeing poison frog (Dendrobates tinctorius) is no exception: its legs are a brilliant blue with black spots, while its back has swirls of bright yellow. It seems counterintuitive at best that such vivid patterns could serve as camouflage, but that's exactly what researchers from the University of Bristol found in their study. First, they took pictures of the frogs in their natural habitat in French Guiana, and then tried to "spot" the frogs using computer models of different animal visual systems. In their models, the frogs were easy to spot close up. But as the simulated eyes moved further away, the patterns started to blend into the background. But computers aren't perfect, so they continued with two studies that tested real eyes. In the first, plastic frogs were placed in the wild on one of four backgrounds—leaf litter, a photo of leaf litter, natural soil, and a colored paper square. The fake frogs were either pattered yellow and black, all yellow, or a completely cryptic brown and black. Both the frog's natural coloration and the designed cryptic patterns lessened the rate at which the faux frogs were attacked by birds, but only when on the leafy backgrounds.