In Japan, Japanese giant salamanders (Andrias japonicus) are known as Osanshouo, which translates as “giant salamander.” The first of these species was discovered in 1820 when Phillip Franz von Siebold, a local doctor on Nagasaki’s Dejima Island, captured and transported one to the Netherlands.
The species is one of the only six species of giant salamanders in the world and has been designated as a special natural monument in 1951, receiving federal protection. With robust bodies and long lifespans, these amazing creatures are extremely special and need to be protected. They are considered to be the third-largest salamander species in the world, growing up to 136 cm or 53 inches and weighing up to 55 pounds (25 kilograms).
Join us as we dive into the world of this remarkable amphibian, exploring its unique biology, its cultural significance, and the conservation efforts underway to protect this vulnerable giant.
Appearance
The Japanese giant salamanders are the third largest salamander species, behind the Chinese giant salamander.
They have wrinkled skin with differing patterns of black and shades of brown. Some can appear pretty dark, while others have light patches of brown. They have flat heads, long, elongated bodies, and wide tails. Distinguishing the sex of the animal can be difficult. All male and female Japanese giant salamanders have small eyes.
The males develop an enlarged cloacal gland during the breeding season.
This unique amphibian has fascinating features that set it apart from other salamanders. It breathes primarily through its skin, the smooth skin acts as a respiratory surface for gas exchange. The oxygen enters its body and carbon dioxide is released without the need for lungs or gills.
This ancient species of salamander belongs to the Cryptobranchid family and are capable of extraordinary regenerative ability, from regrowing skin and bone to even regenerating entire limbs.
Did you know…
Certain amphibians have evolved to become some of the most impressive hunters in the underwater world. However, hunting has become more challenging for some species due to poor eyesight. Without the ability to see their prey, these salamanders are at a huge disadvantage when trying to survive in their aquatic environments, leading them to rely on inefficient methods of sensing their prey. Fortunately, with external sensory organs, these salamanders can now detect vibrations and changes in pressure in the water, allowing them to hunt with greater accuracy and efficiency.
They can reach impressive lengths, up to 5 feet (1.5 meters.) However, most individuals are smaller, typically around 2-3 feet (0.6-0.9 meters).
Habitat
They live in the mountainous regions of Japan. In particular, Hyogo, Shikoku, Okayama, Tottori, Yamaguchi, Gifu, and Oita at elevations of 300-1000 meters are the main areas in which they densely inhabit. These fast-flowing mountain streams are the perfect freshwater habitats for this unique salamander.
In late August, the salamanders congregate at nesting sites, or spawning pits, which simply consist of rocky caverns, burrows, or hollowed impressions within the sandy streambed. Males aggressively compete to occupy these spawning pits.
Large to small headwater streams allow smaller adults to breed in the smaller headwaters, while larger ones breed in the bigger headwaters.
This shy species lives mainly in streams and rivers during the day, and under large rocks along the water’s edge in order to stay concealed from predators. Since Japanese giant salamanders breathe through their skin, the colder, more oxygenated mountain water helps these animals thrive.
Diet
It is a unique carnivore that uses an impressive suction system to capture its prey. By quickly opening and closing its warty mouth and creating negative pressure. This helps them easily engulf whatever they see.
With incredibly slow metabolisms, they can go weeks without eating. The special suction system helps them generate a powerful suction force to capture prey in water simply by dropping one side of their jaw 10 to 40 degrees and not needing saliva.
Their habits include eating various animals, such as fish, frog, insects, crayfish, worms, snails, and small mammals.
Reproduction
The breeding and spawning season for these salamanders is August through September. They head upriver, looking for caverns or big underwater rocks to burrow themselves under. The biggest alpha male’s behavior is interesting. They are primarily concerned with occupying dens and defending them.
Once males have secured the nesting sites, females enter the nesting site to begin the fertilization process. Females approach males and proceed to make a spin-like motion. The female then releases her eggs within the spawning pit while the male fertilizes them
The female salamanders will pick a mate by making a spin-like motion in front of the male. The female then releases her eggs in the spawning area for the males to then fertilize. Mature males provide incredible protection for their eggs! They fiercely guard the spawning pits for up to 15 weeks after fertilization, repelling other male salamanders and potential predators like fish. These selfless guardians even stay in the same pit year after year.
In addition to guarding the nest, he fans the eggs with his tail to maintain constant oxygen flow, and eats any dead eggs, preventing the contamination of his healthy offspring.
Large numbers of offspring are produced each season, so mortality early in life is probably high.
Threats
As a result of water pollution, habitat loss, degradation, dams, concrete banks, and exotic species, the Japanese giant salamander is in danger of extinction. Other larger fish are a threat to smaller adults and the eggs they spawn in the breeding season. But the biggest threat to these salamanders is humans.
This has greatly reduced the population of this iconic species, making it increasingly difficult to keep them safe and ensure their survival.
With ongoing and worsening climate change, Japan could be forced to build more concrete banks and flood-control dams, negatively harming the nesting sites and migration paths for these animals. Additionally, there are some regions of the world where the salamander is considered a delicacy.
8 More Facts about the Japanese Giant Salamander
- The Asa Zoo in Hiroshima was the first to successfully breed Japanese giant salamanders in captivity.
- At the Smithsonian’s National Zoo, Japanese giant salamanders eat fish, shrimp, earthworms, and crayfish.
- Japanese giant salamanders primarily breathe through their skin through the exchanging of gases. Oxygen enters the body, while carbon dioxide is released. These salamanders do have one lung, but it is mainly used for buoyancy in the water.
- It has a single lung, used mainly for buoyancy control rather than breathing.
- These salamanders can live up to 50+ years. However, on average, most live 16 to 20 years long.
- Females release around 400 to 500 eggs in the spawning pit for the males to protect.
- The den master guards over the whole den and consumes eggs and larvae that show signs of failed fertilization, water mold, or death.
- When feeling threatened, these salamander excrete a strong-smelling, milky substance that is toxic to some predators.
- They are nocturnal, which means they are active at nighttime.
FAQs
How many Japanese giant salamanders are left in the world?
Only three members of the giant salamander species are left in the world. China, Japan, and the US. The Japanese giant salamander is on the IUCN Red List of Threatened Species, categorized as a near-threatened or lower-risk species.
Do Japanese giant salamanders have predators?
The Japanese giant salamander has no natural predators, but the biggest threat to this species is humans and climate change. The building of concrete banks and dams to help with increased rainfall is the main cause of their habitats being destroyed.
Are there giant salamanders in the US?
The US is one of three regions where giant salamanders inhabit. The giant salamander known as the Hellbender lives in the eastern US, mainly in Tennessee. Not as large as their cousins from Asia, a fully grown Hellbender can range from 1ft to 2ft long.
Are Japanese giant salamanders poisonous?
Yes, if a Japanese giant salamander feels threatened, they produce a mildly dangerous white mucus that may be harmful or deadly to small predators.
Why is the Japanese giant salamander endangered?
The conservation status of Japanese giant salamander is endangered because of invasive habitat destruction and the effects of climate change. Various marine-based construction projects, like dams, are also an issue for the salamander.
