The Japanese giant salamander is a long-lived, nocturnal predator that breathes through its skin.

Nature · Published 3 October 2026 Swipe more like this →

In short: Hidden in the cold, fast-flowing mountain streams of Japan, this massive amphibian can reach five feet in length and live for nearly 80 years. Despite its size, it relies on a unique respiratory system and a specialized sensory network to hunt in the dark, earning it the nickname big pepper fish.

The Japanese giant salamander, or Andrias japonicus, is a member of the Cryptobranchid family and ranks among the largest amphibians on Earth. These creatures are primarily aquatic, preferring cool, oxygen-rich rivers in Japan's central highland mountainous regions. Because they lack gills as adults, they rely on their wrinkled skin to facilitate gas exchange, absorbing oxygen and releasing carbon dioxide directly from the water. While they do possess a single lung, it serves mainly as a buoyancy control device rather than a primary respiratory organ.

Hunting in near-total darkness, these salamanders compensate for their poor eyesight with a sophisticated lateral line system. Small sensory organs covering their head and body detect minute vibrations in the water, allowing them to track prey like fish, insects, crustaceans, and small mammals. When threatened, they secrete a sticky, pungent, white mucus that smells like Japanese peppers, a defense mechanism that inspired their local name. Their metabolism is remarkably slow, enabling them to survive for weeks without a meal.

Reproduction is a highly territorial affair. During the spawning season from August to October, males compete for dens—caverns or burrows along riverbanks—where they act as 'den masters.' A dominant male will defend his den, where multiple females may lay clutches of 400 to 600 eggs. Once fertilized, the male guards the nest for up to 60 days until the juveniles hatch and venture out on their own. This sedentary, solitary lifestyle is interrupted only by these breeding cycles, where both sexes congregate in specific underwater sites.

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