Japanese Giant Salamander

Andrias japonicus

Japanese Giant Salamander (Andrias japonicus) — Wrinkly River Guardian

The Japanese Giant Salamander (Andrias japonicus) is a fully aquatic amphibian up to about 1.5 m long that lurks in cold mountain streams in western Japan, where big males guard nests of eggs for months.

Habitat

Cold, clear, fast-flowing rocky streams and rivers

Size

Up to about 1.5 m long and 25 kg

Diet

Freshwater crabs, fish, frogs, insects, worms

Range

Western Honshu, parts of Shikoku and northern Kyushu, Japan

Conservation

Vulnerable (IUCN 2022); Special Natural Monument in Japan

Lifespan

50+ years in captivity (52-year record)

Habitat & range

Picture Japan's cold, clear mountain streams running fast over rocky beds. That's home for the Japanese Giant Salamander, found in western Honshu (west of Gifu Prefecture), parts of Shikoku and northern Kyushu, at elevations of roughly 180 to 1,350 meters. It uses everything from rivers 20 to 50 meters wide down to small headwater streams, which seem to be important nurseries for larvae and juveniles. It never leaves the water: adults simply poke their heads up to gulp air, and spend the day tucked under rocks or in burrows in the bank. It is less fussy than you might think. Adults can do well in streams that run past rice paddies, which are full of frogs to eat. But those farm streams usually come with concrete banks and small dams, which leave few places to nest, so they produce few young.

Diet & hunting

These giants are sit-and-wait suction feeders. Adults eat mainly freshwater crabs and other crustaceans, plus fish, frogs, insects, worms and the occasional small mammal. Their tiny, lidless eyes see poorly, so they hunt mostly at night by feel and smell: sense organs in the bumps on their head and body work much like a fish's lateral line, picking up the faint water movements of passing prey. When something comes close, the huge mouth gapes open and sucks it in. A very slow metabolism lets them go weeks without eating. Their mottled brown, warty skin blends into the stream bed, so prey often wanders right up to what looks like a rock.

Behavior & adaptations

Japanese Giant Salamanders hide under rocks by day and come out after dark. Their wrinkled skin, with loose folds along the sides, adds surface area for taking oxygen straight from the cold, oxygen-rich water. When stressed they release a sticky white mucus with a pungent smell said to resemble Japanese pepper, which the Smithsonian's National Zoo says gives them a Japanese name that translates to "big pepper fish." Like many salamanders, giant salamanders can also regrow damaged skin and bone. The fathers do the childcare. In late August and September, big males called den masters claim nest burrows in the stream bank, clean them out and drive off rival males. Females lay strings of about 400 to 500 eggs inside. The den master stays on: he fans the eggs with his tail to bring in oxygen, shakes them with his head and body, and eats the whitish dead or mouldy ones, a behavior researchers named hygienic filial cannibalism. In one filmed nest, the father kept caring for the hatchlings until they dispersed the following spring, about seven months in all.

Conservation

The IUCN lists the Japanese Giant Salamander as Vulnerable (2022 assessment), and it is on CITES Appendix I. Japan has protected it as a Natural Monument since 1951 and as a Special Natural Monument since 1952. Dams and weirs cut rivers into isolated stretches, and concrete banks remove the earthen burrows the males need for nests. The newest threat looks almost identical to it. Chinese giant salamanders were legally imported into Japan until 1980, including about 800 animals brought in for food in 1972. Escaped or released animals have bred with the natives: in Kyoto's Kamo River, hybrids made up 60% of giant salamanders caught in 2008–09 and 92% by 2010–11, and hybrids have since been found in nine prefectures. In 2024 Japan declared Chinese giant salamanders and hybrids invasive alien species. The Wilder TCG card shows the native species; its Chinese cousin has its own Amphibia card.

Fun facts about Japanese Giant Salamander

• When stressed it oozes sticky white mucus that is said to smell like Japanese pepper.
• A den-master dad can care for his young for about seven months, from eggs in late summer until the larvae leave the next spring.
• Fathers eat their own dead or mouldy eggs, which likely stops water mould spreading to the healthy ones.
• One Japanese giant salamander lived for 52 years at Natura Artis Magistra, the zoo in Amsterdam.
• Its family, the Cryptobranchidae, has changed little in about 160 million years.

Japanese Giant Salamander vs Chinese Giant Salamander

The Chinese giant salamander has the edge: it grows bigger, and where it was released in Japan, it and its hybrids are winning.

This matchup is real. Chinese giant salamanders imported into Japan before 1980 escaped or were released into rivers such as Kyoto's Kamo River, right into Japanese giant salamander territory. Chinese giant salamanders are the bigger animals, with a reported record of about 1.8 m against roughly 1.5 m for the Japanese species. Both are den-guarding, suction-feeding river giants with the same courtship, so instead of simply fighting, they interbreed. Hybrids have wider mouths and well-developed biting muscles, and researchers think that helps them grab bigger prey and win fights over nest dens. In the Kamo River, hybrids went from 60% of the salamanders caught in 2008–09 to 92% by 2010–11. The native Japanese giant salamander is losing this one, which is why hybrids are now being removed from Japanese rivers.

Read more about Chinese Giant Salamander.

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