The Congolese Giant Toad shares its rainforest habitat with one of the most fearsome snakes in Africa. But mimicry might be the key to its survival, even without the fangs.
In a feat of ingenious costuming, the wily toad has learned to impersonate the venomous Gaboon viper to fool predators. The findings, published in the Journal of Natural History, mark the first time researchers have recorded a frog emulating a venomous snake.
It’s a form of Batesian mimicry, when a harmless species mimics the appearance and behavior of a venomous one to confuse predators and protect themselves.
Mimicry has long benefited the animal kingdom. There’s a praying mantis species that disguises itself as an orchid to avoid predators and attract prey, and the burrowing owl has learned to copy a rattlesnake’s menacing hiss to scare off squirrels that invade its burrows.
But this is the first frog to learn the trick, and it seems the disguise has worked. Predators avoid the toad far more often than other species, researchers said, even though its size and caloric value make it an enticing meal.
A snake and a toad look alike from above
The Gaboon viper is the largest of its kind in all of Africa at more than 6 feet long and 45 pounds. It’s got the longest fangs of any snake in the world and a potentially fatal bite.
The Congolese giant toad doesn’t have any of those, but it can mimic the deadly viper’s beige-and-brown speckled head. The two share a common habitat in the Democratic Republic of the Congo’s rainforests.
The toad is tan in color, with two brown dots and a dark brown stripe that runs down its back. Its sides are dark brown from the snout to the hind limbs, which mimics the open mouth of a Gaboon viper, and it has slightly raised horn-like “brows” above the eyes, similar to that of a snake.
But the impersonation doesn’t stop there. The toad copies the hissing noise the Gaboon makes to fend off predators with a similar sound that resembles air being released from a balloon, researchers said.
It even lies flat when disturbed, cocking its head and drooping its eyes to appear like the limbless predator when it’s ready to strike.
The camouflage works
From the top, the toad makes a convincing viper. It’s not an exact recreation, but when the model is highly venomous and feared like the Gaboon vipers, predators usually can’t tell the difference, said Eli Greenbaum, study author and director of the University of Texas at El Paso’s Biodiversity Collections.
“It’s not a perfect match,” he told CNN. “But when something like a Gaboon viper is that dangerous, the most visually based predators are probably going to make the calculation– ‘Gosh, if it even looks close to a Gaboon viper, I’m not going to touch it.'”
What’s more, many species that share a habitat with the fearsome serpent are innately afraid of it and avoid it at all costs, particularly primates, so they might instinctively avoid the frog, too, though Greenbaum said the study cannot prove that yet.