Overview

The tiger keelback (Rhabdophis tigrinus), also known in parts of its range as yamakagashi, is a small to medium‑sized colubrid snake notable for its banded coloration and unusual chemical defenses. It is rear‑fanged and produces venom, but it is best known for sequestering toxins from its prey and storing them in specialized skin glands.

Identification and characteristics

This species typically shows alternating dark and light banding that gives rise to the common name. Scales are keeled, producing a rough texture. Adults vary in length but are generally slender. Key distinguishing features include:

  • Bold transverse bands or stripes across the body;
  • Prominent keeled dorsal scales;
  • Rear‑positioned enlarged teeth (opisthoglyphous dentition);
  • Paired nuchal (neck) glands that can hold toxins.

Distribution and habitat

The tiger keelback occurs across parts of East Asia and Southeast Asia. It frequents wetlands, rice paddies, grasslands and edges of streams and ponds where amphibian prey is abundant. Populations and precise range limits vary by region and subspecies.

Behavior, diet and reproduction

Rhabdophis tigrinus is often active by day and may be semi‑aquatic in habits. Its diet consists mainly of amphibians, especially toads and frogs, but it will also take fish and small vertebrates opportunistically. Reproduction is oviparous, with females laying clutches of eggs in suitable cover during the breeding season.

Venom, chemical defense and human interactions

Unlike front‑fanged venomous snakes, the tiger keelback has rear fangs and a delivery mechanism that is typically less efficient for envenoming humans. Its notable defensive strategy involves sequestering bufadienolide toxins from consumed toads and storing them in nuchal glands. When threatened, the snake can exude these toxins as a chemical defense. Human bites are generally not life‑threatening but can cause local effects and, in rare cases, more serious reactions; pets that ingest toxic toads or the snakes themselves can be at risk.

Conservation and significance

Local populations are influenced by wetland drainage, agricultural change and persecution, though the species is not uniformly considered endangered. The tiger keelback attracts scientific interest because of its toxin sequestration and chemical ecology, offering insights into predator–prey interactions and the evolution of defensive strategies.