After not being seen for more than 30 years, the Japanese river otter (Lutra lutra whiteleyi) has been declared extinct by the country's Ministry of the Environment, which also last week declared several other species extinct.

Once numbering in the millions, Japanese river otters—a subspecies of the European or Eurasian otter (L. lutra)—were overhunted for their fur, most of which was sold to foreign traders, and further suffered when their habitats became developed and polluted. The animals grew to about a meter in length and subsisted mainly on fish and shrimp.

The river otter was last officially observed in the wild in a river in the city of Susaki in Japan's Kochi Prefecture in 1979, when a single animal was photographed. The otter remains the official animal symbol of Japan's Ehime Prefecture, home of the poet Masaoka Shiki (1867-1902), who equated himself with otters in his haiku and referred to himself as Dassai Sho-oku Shujin ("Otter Bookstore Owner"). The anniversary of Shiki's death is celebrated every September 19 as Dassai-ki ("Otter's ceremony anniversary"), according to a report in Asahi Shumbun.

Several searches have been conducted for the river otter over the years, although little if any evidence of their continued existence has been found. Yoshihiko Machida, a professor emeritus at Kochi University, told The Mainichi that one case of otter droppings was confirmed in 1999. He said he still has hope that the otter exists and plans to continue searching it.

In addition to the river otter, the Ministry of the Environment also declared as extinct a subspecies of the least horseshoe bat (Rhinolophus pumilus miyakonis), which was last seen in 1971. The Japanese subspecies of the Asian black bear (Ursus thibetanus japonicus) was declared extinct on the island of Kyushu, where it has not been seen since 1957 (it persists elsewhere in Japan). One bird species, one insect species, one shellfish species and two plant species were also listed as extinct. The names of those additional groups were not immediately available.

The otter and horseshoe bat mark the first mammal extinctions in Japan of species that persisted until at least some point during the Showa period, which lasted from 1926 to 1989. Four other Japanese mammals went extinct during what is known as the Meiji restoration period from 1868 to 1912, including two wolf subspecies— the Hokkaido wolf (Canis lupus hattai) and the Honshu wolf (Canis lupus hodophilax)—and two bats— the Okinawa flying fox (Pteropus loochoensis) and the Ogasawara bat (Pipistrellus sturdeei). The International Union for Conservation of Nature and Natural Resources currently lists the two bats as "Data Deficient" rather than "Extinct" as there is some doubt about their taxonomy and whether or not they were actually endemic to Japan.

Photo: No images of a live Japanese river otter exist in the public domain. Museum sample via Wikimedia Commons; stamp, issued in 1974, via StampCommunity.org