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Throughout Earth's history, creatures have evolved extraordinary defenses. A key distinction scientists make is between “poisonous” animals—those that become harmful when touched or eaten—and “venomous” species that actively inject toxins through specialized delivery systems. Understanding this difference is crucial, as it can determine whether an encounter is harmless or lethal.
In 2015, a groundbreaking study published in Current Biology identified two Brazilian frogs that actively weaponize their toxins, challenging long‑standing assumptions about amphibian venom.
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The research spotlighted Bruno’s casque‑headed frog (Aparasphenodon brunoi) and Greening’s frog (Corythomantis greeningi). Their toxins are more potent than those of the infamous pitviper genus Bothrops. What sets these species apart is their sophisticated delivery method: a head‑butt.
Each frog possesses bony spines along its skull—especially near the nose, jaw, and eyes. When threatened, they flex and extend their heads, thrusting the spines forward. As the spines pass through the frogs’ toxic skin glands, they pick up venom and transfer it to the target animal.
During the study, a researcher handling a specimen of Greening’s frog inadvertently received a sting on the hand, experiencing intense pain that radiated across the arm for five hours. Although this frog’s venom is the milder of the two, it is still roughly twice as powerful as that of Bothrops pitvipers.
The authors suggest that these species might be the tip of the iceberg, implying that other poisonous amphibians could also possess venomous capabilities. This discovery invites further research into the prevalence of venom among amphibians.
For more on rare species and conservation, explore our explainers on plant and animal extinction causes and how scientists plan to resurrect the Tasmanian tiger.
