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JAPANESE GIANT SALAMANDER

Japanese giant salamander

The Japanese giant salamander (Andrias japonicus) Is the third-largest salamander and amphibian in the world after the similar and closely related Chinese giant salamander and the South China giant salamander. It can reach lengths of over 1.5 meters (4.9 feet) and live almost 100 years. It almost as big as the Chinese giant salamander, the world’s largest amphibian. Japanese giant salamanders live mainly in rivers in central and western parts of Honshu as well as Shikoku and Kyushu. They used be hunted for food and traditional Asian medicines but now are protected by law, having been designated a special natural monument in 1952.

In August 2010, Japan’s oldest giant salamander, thought to be more than 100 years old, died of old age in the hot spring resort of Yubara in Okayama Prefecture, where it has been on display since 1971. As it had never been properly measured or weighed claims that it weighed 28 kilograms were not taken seriously. A few days earlier a giant salamander that was at least 55 died Kushiro in Hokkaido. It had been on display for 45 years and weighed 19 kilograms. The first living specimen of Japanese giant salamanders that was captured and brought to a Western nation was found by von Siebold in 1829. Von Siebold is credited with the discovery of this species. This giant salamanders he brought back lived at least 52 years in captivity.

Japanese giant salamanders are generally found in streams with clear, cool water. Because of their large size and lack of gills, they need flowing water rich in oxygen. Their largest populations are in Okayama, Hyogo, Shimane, Tottori, Yamaguchi, Mie, Ehime, Gifu, and Ōita Prefectures. at elevations between 180 and 1,350 meters (590 to 4,430 feet). They often reside in cold, swift, mountain streams that provides enough oxygen to diffuse through their epidermis (skin). As is the case other cryptobranchid salamanders, Japanese giant salamanders tend to stay in the water and thus are vulnerable to low water levels. [Source: Wikipedia, Laura Winkler, Animal Diversity Web (ADW) /=]

Japanese giant salamanders are not endangered but they are not that far away from that status. On the International Union for Conservation of Nature (IUCN) Red List they are listed as Near Threatened. In CITES (Convention on International Trade in Endangered Species of Wild) they have no special status. The primary threats they face are loss of habitat, water pollutions from agricultural chemical runoff and other forms of degradation of their water environment. Local fishermen complain that Japanese giant salamanders consumes small sweetfish that inhabit the same mountain streams that they do.

Giant Japanese Salamander Characteristics

Japanese giant salamander range

Giant Japanese salamanders weigh up to 25 kilograms (55 pounds) and reach 1.5 meters (4.9 feet) length. The largest wild specimen on record weighed 26.3 kilograms (58 pounds) and was 1.36 centimeters (4.46 feet) long.They are cold blooded (ectothermic, use heat from the environment and adapt their behavior to regulate body temperature) and heterothermic (having a body temperature that fluctuates with the surrounding environment). Sexual Dimorphism (differences between males and females) is present: The body shape of males is a little different than that of females. Adult males develop enlarged cloacal glands during the breeding season. They also have a larger and wider head in proportion to their body than female. But generally it is difficult to distinguish males and females outside of the breeding season.[Source: Laura Winkler, Animal Diversity Web (ADW) /=\, Wikipedia]

The long and squat body of Japanese giant salamanders is covered with a wrinkled grey, black, and green skin that provides good camouflage at the bottom of streams where they spend most of their time. The body surface is covered with numerous small warts, with distinctive warts concentrating on its head. The mouth extends across the width of its head, and can open to the width of its body. A. japonicus possesses large skin folds on its neck that effectively increase its overall body surface area

Their tail is long and wide, and their legs are relatively short. The eyes of the Japanese giant salamanders are small and lidless eyes. They sit on the top of the wide, flat head and do not do so much as these salamanders have poor vision. Gas exchange occurs through the epidermis. The wrinkles of the warty skin provide increased surface area, facilitating the exchange of carbon dioxide and oxygen with the water. Capillaries run close to the surfaces of the skin, allowing for the easy diffusion of gases. They differ from other closely related species in that they lack gill openings and also have unique modifications with their branchial structures. /=\

Japanese giant salamanders can be distinguished from the Chinese giant salamanders by the arrangement of tubercles on the head and throat. The tubercles are larger and more numerous on Japanese giant salamanders while those on Chinese giant salamanders are mostly single and irregularly scattered tubercles. The snout of Japanese giant salamanders is also more rounded, and the tail is slightly shorter.

Giant Japanese Salamander Diet and Hunting

Japanese giant salamanders in Tottori Prefecture. showing notable color variation among individuals within the same population

Japanese giant salamanders are recognized as carnivores (eat meat or animal parts), piscivores (eat fish) and insectivores (eat insects). They are known to consume fish, frogs, other small amphibians, insects, non-insect arthropods, crustaceans, worms, and even, occasionally, small mammals..

Japanese giant salamanders are best described as slow-moving, generalist ambush hubters. They can open and close their warty mouth with lightning speed while sucking in prey. They do this by creating negative pressure within the mouth, which produces asymmetrical suction. Cryptobranchid salamanders that suck asymmetrically drop one side of their jaw 10 to 40 degrees in order to suck in their prey.

The slow metabolism of Japanese salamanders allows them to live without consuming food for up to weeks at a time. Because these salamanders feed in water, saliva is not needed. While habitat degradation threatens Japanese giant salamanders, they can inhabit disturbed streams surrounded by rice paddy fields. They appear to do well in such streams as the paddy fields provide habitats for frogs, which serves as primary source of food for adult giant salamanders in such streams. However, streams surrounded by rice paddy fields are typically characterized by agricultural dams and concrete stream banks, which likely have a negative impact on their reproduction.

Giant Japanese Salamander Behavior

Japanese giant salamanders are natatorial (equipped for swimming), nocturnal (active at night), motile (move around as opposed to being stationary), sedentary (remain in the same area) and territorial (defend an area within the home range). Unlike usual pond-breeding salamanders whose juveniles migrate to land after losing their gills through metamorphosis, Japanese giant salamanders stay in water even after metamorphosis and breach their head above the surface to obtain air without venturing onto land. They also absorbs oxygen through their skin. The main form of predation they need to concern themselves with is fish feeding on their eggs. [Source: Wikipedia, Laura Winkler, Animal Diversity Web (ADW) /=]

Japanese giant salamander skeleton

Japanese giant salamanders usually sleep underneath stream rocks during the day. Their normal movement is walking on the bottoms of streams. An undulating, fish-type of movement is used to quickly travel short distances. Especially in calmer water, Japanese giant salamanders employ side-to-side movements to keep water flowing over their skin so that deoxygenated water moves away and oxygen-rich water replaces it.

Japanese giant salamanders are territorial. It is not uncommon for large males to kill smaller rivals in defense of spawning pits. As a means of defense, Japanese giant salamanders release milky secretions that smell like the Japan pepper plant. These strong-smelling secretions quickly harden into a gelatinous substance when exposed to air.

Japanese giant salamanders sense and communicate with touch and chemicals usually detected by smelling. Their small eyes provide limited vision and they are mainly active at night anyway so they rely on their senses of smell and touch to perceive their environments. Japanese giant salamanders have pecial sensory cells covering their skin from head to toe. This lateral line system of sensory cells, which have hair-like shapes. detect minute vibrations in the environment, and are quite similar to the hair cells of the human inner ear.

Giant Japanese Salamander Metamorphosis

Japanese giant salamanders grow continuously throughout their life. As is the case with other amphibians, their life cycle is characterized by metamorphosis — a process of development in which individuals change in shape or structure as they grow. [Source: Laura Winkler, Animal Diversity Web (ADW) /=]

Japanese giant salamanders undergo three developmental stages: egg, larva, and their adult form. Their development and life cycle is characterized by neoteny (juvenilization, delaying or slowing of the physiological development) and paedomorphism (retainment of juvenile characteristics by an adult).

Metamorphosis is not complete. Adults do not develop eyelids, and retain a single pair of closed gill slits on the neck. In addition, Japanese giant salamanders retain their larval teeth for life, and have lungs which are vestigial, performing no gas exchange.

Giant Japanese Salamander Mating, Reproduction and Offspring

Japanese giant salamanders are polygynous (males have more than one female as a mate at one time). They are oviparous, meaning that young are hatched from eggs, and reproduction is external, meaning the male’s sperm fertilizes the female’s egg outside her body. Japanese giant salamanders engage in seasonal breeding: breeding once a year, usually beginning in early August. The number of eggs ranges from 400 to 500. Eggs usually measure six millimeters by four millimeters, and are mostly yellow in color. They are held together with a string-like substance and resemble threaded beads on a string. The time to hatching ranges from 12 to 15 weeks. [Source: Laura Winkler, Animal Diversity Web (ADW) /=]

In late August, Japanese giant salamanders begin the reproductive process by congregating at nesting sites, or spawning pits, which are typically rocky caverns, burrows, or hollowed impressions within a streambed. Males may compete fiercely to occupy these spawning pits. Once males have secured the nesting sites, females enter the nesting site to begin the fertilization process which starts with females approaching the males and making a spinning motion. The female then releases her eggs within the spawning pit and the male fertilizes them. More than one female may release eggs into the same spawning pit. Males guard the eggs in the spawning pits until they hatch. They protect the eggs from other male salamanders and predators such as fish. Males often aggressively defend and occupy a particular spawning pit for many years. Smaller males have been killed and eaten by larger males during battles for spawning pit.

Both sexes are involved in parenting. Pre-birth provisioning is done by females and protecting is done by males. Females provision eggs with large quantities of nutrients, ensuring their survival. Males contribute to the survival of offspring by guarding the eggs in the spawning pits until the eggs have hatched. The age at sexual maturity for Japanese giant salamanders is not known, although based on observations of male competition, successful breeding requires a large size, at least for males.

Interbreeding of Japanese and Chinese Giant Salamanders

Chinese giant salamanders and Japanese giant salamanders are very difficult to tell part. Before an international ban on trade of these salamanders came into effect many Chinese giant salamanders — which are raised in farms in China for human consumption — were imported live to Japan for food. One dealer in Okayama obtained 800 of them for sale to restaurants. Some of those that were imported escaped or were released and have interbred with the Japanese species and competed with them for nesting sites and food.

Many of the Japanese giant salamanders seen in rivers in central and western Japan are actually Chinese giant salamanders, which biologists regard as threat to their Japanese cousins. DNA analysis of giant salamanders caught in the wild reveal that many are Chinese not Japanese, with some Chinese ones even showing up in the Tokyo area. One 140-centimeter Chinese giant salamander in the 1990s in Saitama Prefecture’s Arakawa River is still alive and is the largest salamander in captivity in Japan.

In July 2010, the Smithsonian National Zoo announced it would set up a breeding center for Japanese giant salamanders.

Image Sources: Wikimedia Commons

Text Sources: Animal Diversity Web animaldiversity.org ; National Geographic, Live Science, Natural History magazine, David Attenborough books, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Discover magazine, The New Yorker, Time, BBC, CNN, Reuters, Associated Press, AFP, Lonely Planet Guides, Wikipedia, The Guardian, Top Secret Animal Attack Files website and various books and other publications.

Last updated March 2025