A species of non-poisonous frog in the lowland rain forest of Ecuador adopts the coloring of its poisonous neighbor to ward off predators. That’s standard mimicry as practiced by species around the world.
Graduate student Catherine Darst worked for parts of three years in Ecuador studying poison dart frogs.
Indeed, the frog’s only defenses are “speed and false advertising,” said Catherine Darst, a graduate student at The University of Texas at Austin who spent parts of three years studying the frogs and their protection patterns.
She found that where three frog species—more poisonous, less poisonous and harmless—overlap, the harmless frog adopts the coloring of the less poisonous frog.
The finding was not standard mimicry. Darst called it, “totally bizarre.”
But, it turns out, the harmless frog’s strategy is pretty smart, she said.
Predators who have had the unpleasant experience of tasting the more poisonous frog, avoid both the color patterns of both types of poisonous frogs.
So, by looking like the less poisonous frog, the harmless frog gets double protection.
Darst and Dr. Molly Cummings, an assistant professor of integrative biology, published the findings in the March 9 issue of Nature.
Top: the harmless mimic, Allobates zaparo. Middle: Epipedobates bilinguis, the toxic poison dart frog that A. zaparo mimics when all three frogs occur together. Bottom: E. parvalus, the more abundant, more toxic poison dart frog.
Images courtesy David Cannatella
“We’ve uncovered a new mechanism involved in mimicry process,” Cummings said. “A mimic species can actually become a different color pattern if it can enjoy the protection of the predator generalization brought on by more toxic species in the community.”
Darst said the predators are reacting the way someone who has had a bad case of food poisoning. If you get just a little sick after eating bad shellfish, you’ll avoid shellfish for a while, but still eat fish. But if the shellfish makes you really, really sick, you’ll probably steer clear of any seafood for a longer time.
The frogs are about as big as your thumb. They have red spots on their backs and the less poisonous frogs have splashes of yellow on their legs.
The frogs’ poisonous skin alkaloids are sequestered from their diet of tiny, leaf litter insects. Darst testifies to the strength of the poison.
“If you touch the frogs, it (the poison) kind of numbs your finger pretty well,” Darst said, adding. “I’ve tasted the frogs and they have a bitter taste.”
