In Japan, Japanese giant salamanders 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 136cm or 53 inches and weighing up to 55 pounds (25kilograms).
Appearance
The Japanese giant salamanders are the third largest salamander species, behind the Chinese giant salamander. The largest known is recorded to be almost 5ft long and 58 pounds. 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. The males will develop an enlarged cloacal gland during the breeding season. All male and female Japanese giant salamanders have small eyes.
The giant Japanese salamander is one of the most unique amphibians on the planet. It has a fascinating feature that sets it apart from other salamanders — it breathes primarily through its skin! Its smooth skin acts as a respiratory surface for gas exchange, meaning oxygen can enter 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 can survive in freshwater streams and rivers, where they feed on fish, frogs, crustaceans, and small mammals. They are capable of extraordinary regenerative feats — from regrowing skin and bone to even regenerating entire limbs.
Habitat
Japanese giant salamanders live in the mountainous regions of Japan. In particular, Hyogo, Okayama, Tottori, Yamaguchi, Gifu, and Oita are the main areas in which they densely inhabit. These fast-flowing mountain streams are the perfect freshwater habitats for the Japanese giant salamander. 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 they hide 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
A Japanese giant salamander 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, the Japanese giant salamander can easily engulf whatever it sees. With this special suction system, the Japanese giant salamander can become a generalist predator, consuming prey from different sources. Unlike other animals who need saliva to feed, these salamanders generate a powerful suction force to capture prey in water simply by dropping one side of their jaw 10 to 40 degrees.
Japanese giant salamanders have habits that include eating a wide variety of animals, including fish, insects, crayfish, worms, snails, and small mammals. With incredibly slow metabolisms, they can go weeks without eating.
Certain amphibians have evolved over time to become some of the most impressive hunters in the underwater world. But for some species, hunting has become more challenging 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.
Reproduction
The breeding and spawning season for these salamanders is August through October. 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.
Males will compete aggressively to fill up the spawning pits. After the males have occupied the nest, the females will begin the fertilization process.
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. Male salamanders 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.
Threats
There are two main threats to the Japanese giant salamander. Firstly, 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 and not their consumption of them.
As a result of pollution, habitat loss, dams, concrete banks, and exotic species, the Japanese giant salamander is in danger. 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, which will negatively harm the nesting sites and migration paths for these animals.Additionally, there are some regions of the world where the salamander is considered a delicacy.
Facts about the Japanese Giant Salamander
- 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.
- These salamanders can live up to 50+ years. However, on average, most live 16 to 20 years long.
- Female Japanese salamanders release around 400 to 500 eggs in the spawning pit for the males to protect.
- The alpha salamander that guards over the whole den will consume eggs and larvae that show signs of failed fertilization, water mold, or death.
- When feeling threatened, the Japanese giant salamander can excrete a strong-smelling, milky substance that is toxic to some predators.
- Japanese giant salamanders 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 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.
