Scientists have discovered two species of Brazilian frogs that can inject venom directly into potential predators using tiny spines protruding from the front of their skulls. These two species have been known to researchers for decades. In fact, one was first described in as early as 1896. But scientists didn’t know about the venomous traits of these frogs until the less poisonous of the two jabbed a scientist.

These Brazilian Frogs Are More Poisonous Than Pit Vipers

What’s the difference between ‘poisonous’ and ‘venomous’?

Findings of the study were published in the journal Current Biology. Brazilian researcher Carlos Jared of the Instituto Butantan in São Paulo suffered intense pain for about five hours on his hands after handling Corythomantis greeningi, the less poisonous of the two. Later, he and his colleagues figured out that the little frog had released toxins from its skin into his hand.

Many tropical frogs have long been known to secrete poison out of their skin. They prove toxic to predators when eaten. Until now, no frog was known to have a well-developed “delivery mechanism” to inject its venom into the predator. Frogs that have poison, but no delivery mechanism are termed poisonous. But these two Brazilian frogs have well-developed delivery mechanisms, making them venomous like snakes and scorpions.

These frogs have no natural predators in the wild

Fortunately, Carlos Jared was bit by the less poisonous one. The second species Aparasphenodon brunoi is deadly. Just one gram of its venom is enough to kill 300,000 mice or at least 80 humans. However, A. brunoi doesn’t produce this much toxin, and the amount transferred by the spines into the target’s wounds could be even smaller. Edmund Brodie of Utah State University, a co-author of the study, said the skin secretions of A. brunoi are “more venomous than those of the deadly pit vipers.”

Scientists have described them as the world’s first venomous frog species. Surprisingly, neither species is known to have any natural predators, and now scientists know why. Edmund Brodie said findings of the study will help understand the biology of amphibians and their relationship with natural predators.