What question did this study set out to answer?

The aim is to address hybridization between Japanese Giant Salamanders and introduced Chinese Giant Salamanders as a conservation issue.

April 27, 2026SHILAP Revista de lepidopterología0 citationsOpen Access

Rise of hybrid giants: invasive hybridization as an urgent conservation challenge to the Japanese Giant Salamander

MTMizuki K. Takahashi ZSZenkichi Shimizu

Key Points

The aim is to address hybridization between Japanese Giant Salamanders and introduced Chinese Giant Salamanders as a conservation issue.
Investigated the historical context of Chinese Giant Salamander imports in Japan.
Analyzed the effects of hybridization on JGS populations.
Assessed regulatory and conservation challenges related to hybrids.
Hybrid swarms of giant salamanders were found in nine prefectures, complicating eradication efforts.
Hybrids possess larger mouths and stronger bite forces, potentially outcompeting JGSs.
Recommendations stress case-specific management plans to preserve genetic integrity and ecosystems.

Abstract

The Japanese Giant Salamander (JGS; Andrias japonicus ) is an apex aquatic predator endemic to streams in Western Japan. It is threatened with extinction by various factors, and hybridization with introduced Chinese Giant Salamanders (multiple Andrias spp.; CGSs) has become an urgent issue. Historically, CGSs were legally imported into Japan until 1980, when Japan joined CITES. A well-known mass CGS importation occurred in 1972, which is likely to be one of the sources of the invasive hybridization. Hybrid giant salamanders (i.e., hybrid giants) were first identified in Kyoto in 2010. To date, hybrids have been found in nine prefectures, and complete eradication of hybrids from Japan appears difficult. Although hybrids and JGSs are similar in appearance, some differences exist, including those in dorsal patterns and head shape. The larger mouths with potentially stronger bite force likely enable hybrids to outcompete JGSs. However, the ecological impacts of hybrids remain largely unknown. Similarity in reproductive behaviors between the parental species explains successful hybridization. Long-term data from Mie Prefecture showed that hybrid swarms can form rapidly without management interventions. Conservation challenges include illegal releases of hybrids, insufficient initiatives by federal and local governments, and hurdles to conducting field surveys. Practical preservation of a functional ecosystem requires a viable top-predator population, including both JGSs and their ecologically equivalent hybrids. Nonetheless, Japanese citizens are legally obligated to protect the JGS’s genetic integrity as a designated Special Natural Monument. We recommend case-specific plans depending on hybridization progression, river conditions, and habitat connectivity. Finally, we remind that failure to address habitat destruction and climate change as fundamental conservation issues would defeat the ultimate goal of protecting biodiversity, functional ecosystems, and the national treasure.

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