What can stomach a toxic frog?

STRI/DICYT Eating a Strawberry Dart Poison Frog is supposed to be a really bad idea. As a reminder to potential predators, the tiny amphibian advertises its toxicity with its loudly colored skin — bright red in mainland Central America and a rainbow of variations on the islands of Panama’s Bocas del Toro Archipelago. Until recently, it was thought the tiny Oophaga pumilio had no regular predators. That may not be the case.

As part of a team from Tulane University studying the frog on Bastimentos Island, postdoctoral researcher Matthew Dugas photographed a snake consuming an orange-and-black mottled O. pumilio. The images, published in Herpetology Notes, are some of the first photos showing snake predation. They contribute to the small body of evidence pointing to Strawberry Dart Poison Frog predation.

“Very little is known about natural predators of these frogs but clearly some predators can overcome the frog’s alkaloid defenses,” said Ralph Saporito, of John Carroll University, who photographed a Rufous Motmot feeding on O. pumilio in Costa Rica in 2011. His lab is currently setting up experiments with snakes and birds to learn if O. pumilio is a regular menu item for predators and to figure out how the predators tolerate frog toxins.

Saporito asks if the toxins are concentrated in some particular predator body part — muscle or liver, for example. He also wonders if predators are capable of sequestering toxins themselves and using them for defense.

On the same day Dugas photographed the predatory event, a colleague saw another snake of the same species (an Adorned Graceful Brown Snake, or Rhadinaea decorata) strike at a frog. The scientist did not see other predation events during seven subsequent visits to the same site over six weeks. “I’m not sure how common this is, but it is awfully important to figure it out when studying the evolution of toxins and warning coloration,” said Dugas, who was hosted by STRI’s Bocas del Toro Research Station.