There must be some otter way

Kyoto, Japan -- The fuzzy and adorable otter has experienced a surge in popularity in recent years. These aquatic mammals are friendly, playful, and make cute cooing sounds, so their social media stardom seems only natural.

Sadly, this enthusiasm for otters has a dark side: they are targets for smuggling. In Japan, their popularity has raised demand for them as pets and as featured species at exotic animal cafés, making Japan one of the most prominent destinations for captive otters with ambiguous origins.

Asian small-clawed otters -- the species most common at Japanese zoos and cafés -- are native to South and Southeast Asia. They are classified as vulnerable by the IUCN Red list and their international trade for commercial purposes is prohibited. Yet they continue to be captured and smuggled into Japan, with Thailand as the main source of this illegal trade.

To address this, a team of researchers at Kyoto University, in collaboration with scientists in Thailand, set out to understand where exactly these otters are coming from.

"Collaborative research can help identify the origins of otters kept in Japan and hot spots of illegal trade in Thailand, thus encouraging legal control in both countries," says first author Mayako Fujihara.

To determine the geographic origins of Japan's captive otters, the team compared their mitochondrial DNA with that of otters living in the wild in Thailand. The otters in Japan used in this study included captive otters at exotic animal cafés, those legally housed in zoos and aquariums, and otters seized at airport customs upon arrival in Japan.

The research team found that the geographical origins of captive otters at exotic animal cafés differ from those kept in Japanese zoos and aquariums. Their origins also imply that café and pet demand puts the endangered Asian small-clawed otters at risk.

Ironically, otters are not exactly a novelty in Japan. River otters, or kawauso, play a major role in Japanese folklore as shapeshifters known for their mischievous and playful nature. This mythical otter is based on the Japanese river otter, which used to be common in Japan, before hunting for pelts and habitat destruction caused it to be declared extinct in 2012 after not having being sighted in over 30 years.

"It is precisely because Japan's endemic otter species has gone extinct that we aim to continue conducting research that will help protect other vulnerable species," says Fujihara.

This collaborative effort reveals valuable information that can help authorities in both Japan and Thailand prevent otters from being captured and exploited. Beyond that, the geographical information this study provides can be used to promote genetic management in conservation breeding programs in Japanese zoos and aquariums.

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The paper "Molecular tracing of the geographical origin of captive Asian small-clawed otters in Japan" appeared on 8 March 2025 in Conservation Science and Practice, with doi: 10.1111/csp2.70010

About Kyoto University

Kyoto University is one of Japan and Asia's premier research institutions, founded in 1897 and responsible for producing numerous Nobel laureates and winners of other prestigious international prizes. A broad curriculum across the arts and sciences at undergraduate and graduate levels complements several research centers, facilities, and offices around Japan and the world. For more information, please see: http://www.kyoto-u.ac.jp/en