Reptiles
Keelback
Rhabdophis tigrinus · also called tiger keelback, Japanese keelback
Most predators avoid a toad’s toxic skin secretions entirely, but a keelback does something stranger: it eats the toad anyway, then quietly stores those same toxins in glands along its own neck, turning a meal’s chemical defenses into a permanent weapon of its own.
Overview
The keelback, Rhabdophis tigrinus, is a toad-eating snake native to wetland habitat across East Asia. Its ability to sequester dietary toxins from toad prey for its own defense represents a genuinely rare strategy among snakes.
Borrowed poison, real protection
Rather than evolving its own toxins from scratch, the keelback simply takes them from its prey, a defensive shortcut that ties the strength of its own protection directly to how many toxic toads happen to live in its particular corner of East Asia.
Status
Least Concern — widespread and stable across suitable wetland habitat throughout its East Asian range.
Keelback: common questions
How does a keelback get its defensive toxins?
A keelback sequesters defensive toxins called bufadienolides directly from the toads it eats, storing them in specialised glands along the back of its neck for its own protection, a genuinely unusual case of one animal deliberately repurposing a food source's chemical defenses as its own.
Why does a keelback present its neck instead of biting when threatened?
When threatened, a keelback often arches and presents the back of its toxin-loaded neck toward a predator rather than attempting to bite, a defensive display built specifically around the borrowed toad toxins stored in its neck glands, which can be genuinely harmful if a predator bites down on them.
Does the toxicity of a keelback depend on what it eats?
Yes, the toxicity of an individual keelback's neck glands can vary depending on how many toxic toads it has consumed in a given area, since populations with limited access to toxic toad prey accumulate noticeably less defensive toxin than populations feeding heavily on toads.
Is a keelback venomous on its own, aside from the toad toxins?
Yes, in addition to its borrowed toad toxins, a keelback also possesses its own mild venom delivered through rear fangs, though bites to humans are relatively uncommon, and its stolen toad toxins remain the more distinctive and well-studied part of its defense strategy.