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| Subspecies: | Unknown |
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| Est. World Population: | |
| CITES Status: | NOT LISTED |
| IUCN Status: | Vulnerable |
| U.S. ESA Status: | NOT LISTED |
| Body Length: | |
| Tail Length: | |
| Shoulder Height: | |
| Weight: | |
| Top Speed: | |
| Jumping Ability: | (Horizontal) |
| Life Span: | in the Wild |
| Life Span: | in Captivity |
| Sexual Maturity: | (Females) |
| Sexual Maturity: | (Males) |
| Litter Size: | |
| Gestation Period: | |
Habitat:
This large salamander is entirely aquatic and nocturnal. It lives and breeds in small (1–4 m wide) to large (20–50 m wide) rivers, preferring clear water with rocky or gravel substrate, usually in forested areas. It has occasionally been found in rivers in urban areas. They hide themselves in burrows and rocky crevices along the water's edge. The adults can tolerate a wide variety of habitats, but are not necessarily able to breed in these habitats. Through environmental DNA and field surveys, Bjordahl et al. (2020) found that small tributary streams are more important than previously thought, especially for smaller breeding adults and larval and juvenile development.
Females lay their eggs in a string, underwater and the larvae then develop in the streams. Males stay with the eggs and larvae and provide parental care until the following Spring up to a seven month period (Okada et al. 2015, Takahashi et al. 2016). Cryptobranchidae and Sirenidae are the only two (out of ten) salamander families known to provide male parental care and hence species such as the Japanese Giant Salamander, are unique and ecologically important (M. Takahashi pers. comm. April 2021).
It takes 4 to 6 years for larvae to complete metamorphosis and become a juvenile. It takes another approximately 10 years for these juveniles to start joining reproductive events. When stream conditions are favourable, it may take only 10 years for a hatchling to become reproductively active. There are records of tracking the same individuals for up to around 40 years, and those individuals were initially found as adults, indicating that they are 50 to 60 years old at least. While there is no longevity data available, it is suspected that they can live for up to 100 or more years. Males tend to breed annually while some females breed biannually or switch between annual and biannual. Based on this data provided by M. Takahashi and S. Okada (pers. comm. February 2021), the generation length is estimated to be likely to be between 20 to 60 years, and for the purposes of this assessment, a value of 30 years is used.
Females lay their eggs in a string, underwater and the larvae then develop in the streams. Males stay with the eggs and larvae and provide parental care until the following Spring up to a seven month period (Okada et al. 2015, Takahashi et al. 2016). Cryptobranchidae and Sirenidae are the only two (out of ten) salamander families known to provide male parental care and hence species such as the Japanese Giant Salamander, are unique and ecologically important (M. Takahashi pers. comm. April 2021).
It takes 4 to 6 years for larvae to complete metamorphosis and become a juvenile. It takes another approximately 10 years for these juveniles to start joining reproductive events. When stream conditions are favourable, it may take only 10 years for a hatchling to become reproductively active. There are records of tracking the same individuals for up to around 40 years, and those individuals were initially found as adults, indicating that they are 50 to 60 years old at least. While there is no longevity data available, it is suspected that they can live for up to 100 or more years. Males tend to breed annually while some females breed biannually or switch between annual and biannual. Based on this data provided by M. Takahashi and S. Okada (pers. comm. February 2021), the generation length is estimated to be likely to be between 20 to 60 years, and for the purposes of this assessment, a value of 30 years is used.
Range:
This species is endemic to Japan and is distributed in western Honshu (Chubu, Kinki and Chugoku regions) and parts of Shikoku and Kyushu. It occurs from 30–1,000 m asl.
Conservation:
Conservation Actions In-Place
It has been designated as a special natural monument in Japan and is totally protected, and its habitats are protected in some areas. Asa Zoo has been breeding this species in captivity since 1979 (although no re-introductions have taken place to date), it also rescues individuals from degraded habitats, and has conducted other projects such as creating "salamander ladders" in streams affected by dams. Asa Zoo has partnered with several institutions internationally in the conservation of this species, including sending their captive-reared individuals to multiple zoos in the United States (e.g. San Antonio Zoo in the mid-1990s, Detroit Zoological Society in 1999, Smithsonian's National Zoo in 2009, Honolulu Zoo in 2015) where the species is part of conservation breeding programs. It is listed in CITES Appendix I. The species has been designated as Vulnerable in the Japanese Red list.
Conservation Needed
Protection of the species' natural habitat from urbanization and environmental destruction, including forests along streams where the species inhabits is needed. Human transportation of wild populations is currently prohibited, however improved monitoring and enforcement of the law is needed. Protection or enclosure of genetically intact native populations from introduced Chinese Giant Salamanders is required.
Research Needed
Research is needed to examine genetic diversity in the whole distribution by using nuclear genome markers, to determine the degree of genetic pollution from the introduced Chinese Giant Salamanders, and evaluate population recruitment by age estimation. In addition, further surveys are needed throughout the species' range, particularly in unsurveyed streams that may potentially provide suitable habitat for this species, in order to ensure their conservation and prevent any further alterations of these streams (M. Takahashi pers. comm. April 2021).
It has been designated as a special natural monument in Japan and is totally protected, and its habitats are protected in some areas. Asa Zoo has been breeding this species in captivity since 1979 (although no re-introductions have taken place to date), it also rescues individuals from degraded habitats, and has conducted other projects such as creating "salamander ladders" in streams affected by dams. Asa Zoo has partnered with several institutions internationally in the conservation of this species, including sending their captive-reared individuals to multiple zoos in the United States (e.g. San Antonio Zoo in the mid-1990s, Detroit Zoological Society in 1999, Smithsonian's National Zoo in 2009, Honolulu Zoo in 2015) where the species is part of conservation breeding programs. It is listed in CITES Appendix I. The species has been designated as Vulnerable in the Japanese Red list.
Conservation Needed
Protection of the species' natural habitat from urbanization and environmental destruction, including forests along streams where the species inhabits is needed. Human transportation of wild populations is currently prohibited, however improved monitoring and enforcement of the law is needed. Protection or enclosure of genetically intact native populations from introduced Chinese Giant Salamanders is required.
Research Needed
Research is needed to examine genetic diversity in the whole distribution by using nuclear genome markers, to determine the degree of genetic pollution from the introduced Chinese Giant Salamanders, and evaluate population recruitment by age estimation. In addition, further surveys are needed throughout the species' range, particularly in unsurveyed streams that may potentially provide suitable habitat for this species, in order to ensure their conservation and prevent any further alterations of these streams (M. Takahashi pers. comm. April 2021).