Habitat and Ecology
A Japanese zoologist interviewed in the 1950s gave the lengths of adult males as 2.5 m and adult females as 1.4 m, and reported a four-month-old pup as being 65 cm long and 9 kg. A review in the late 1950s listed eight specimens as existing in museums, with none of these in Japan.
Very little information is available on these animals, although they are assumed to be similar to the California Sea Lion. Anecdotal information suggests that the species was known to occupy coastal areas, was rarely found more than 16 km out to sea, frequently hauled out throughout the year, bred mainly on flat, open, sandy beaches, and sometimes in rocky areas, and they were said to be good divers that fed on fish. However, no detailed information or results of studies are available to support these observations.
IUCN Red List Assessment
Red List Category
Red List Criteria
- 1994Extinct(Groombridge 1994)
- 1990Extinct?(IUCN 1990)
- 1988Endangered(IUCN Conservation Monitoring Centre 1988)
- 1986Endangered(IUCN Conservation Monitoring Centre 1986)
Relevance to Humans and Ecosystems
Japanese sea lion
Prior to 2003, it was considered to be a subspecies of California sea lion as Zalophus californianus japonicus. However, it was subsequently reclassified as a separate species. Some taxonomists still consider it as a subspecies of the California sea lion. It has been argued that Z. japonicus, Z. californianus, and Z. wollenbaeki are distinct species because of their distant habitation areas and behavioral differences.
They inhabited the Sea of Japan, especially around the coastal areas of the Japanese Archipelago and the Korean Peninsula. They generally bred on sandy beaches which were open and flat, but sometimes in rocky areas.
Currently, several stuffed specimens can be found in Japan and in the National Museum of Natural History, Leiden, the Netherlands, bought by Philipp Franz von Siebold. The British Museum possesses a pelt and four skull specimens.
Male Japanese sea lions were dark grey and weighed about 450 to 560 kg, reaching lengths of 2.3 to 2.5 m; these were larger than male California sea lions. Females were significantly smaller at 1.64 m long with a lighter colour than the males.
Range and habitat
Japanese sea lions were primarily found in the Sea of Japan along the coastal areas of the Korean Peninsula, the mainlands of the Japanese Archipelago (both sides on the Pacific Ocean and Sea of Japan), the Kuril Islands, and southern tip of the Kamchatka Peninsula.
Old Korean accounts also describe that the sea lion and spotted seal (Phoca largha) were found in broad area containing the BoHai Sea, the Yellow Sea, and Sea of Japan. The sea lions and seals left relevant place names all over the coast line of Japan, such as Ashika-iwa (アシカ岩, sea lion rock) and Inubosaki (犬吠崎, dog-barking point) because of the similarity of their howls.
Lifestyle and reproduction
They usually bred on flat, open, and sandy beaches, but rarely in rocky areas. Their preference was to rest in caves.
Many bones of the Japanese sea lion have been excavated from shell middens from the Jōmon period in Japan while an 18th-century encyclopedia, Wakan Sansai Zue, describes that the meat was not tasty and they were only used to render oil for oil lamps. Valuable oil was extracted from the skin, its internal organs were used to make expensive oriental medicine, and its whiskers and leather were used as pipe cleaners and leather goods, respectively. At the turn of the 20th century, they were captured for use in circuses.
Harvest records from Japanese commercial fishermen in the early 1900s show that as many as 3,200 sea lions were harvested at the turn of the century, and overhunting caused harvest numbers to fall drastically to 300 sea lions by 1915 and to few dozen sea lions by the 1930s. Japanese commercial harvest of Japanese sea lions ended in the 1940s when the species became virtually extinct. In total, Japanese trawlers harvested as many as 16,500 sea lions, enough to cause their extinction. Submarine warfare during World War II is even believed to have contributed to their habitat destruction. The most recent sightings of Z. japonicus are from the 1970s, with the last confirmed record being a juvenile specimen captured in 1974 off the coast of Rebun Island, northern Hokkaido.
Population revival efforts
In 2007, the South Korean Ministry of Environment has announced that South and North Korea, Russia, and China will collaborate on bringing back the Japanese sea lion in the Sea of Japan. The National Institute of Environmental Research of Korea was commissioned to conduct feasibility research for this project. If the animal cannot be found, the South Korean government plans to relocate California sea lions from the United States. The South Korean Ministry of Environment supports the effort because of the symbolism, national concern, the restoration of the ecological system, and possible ecotourism.
- Aurioles, D. & Trillmich, F. (IUCN SSC Pinniped Specialist Group) (2008). Zalophus japonicus. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 7 January 2009.
- (Japanese) Zalophus californianus japonicus (CR), Red Data Book, Japan Integrated Biodiversity Information System, Ministry of the Environment (Japan). "The Japanese sea lion (Zalophus californianus japonicus) was common in the past around the coast of the Japanese Archipelago, but declined rapidly after the 1930s from overhunting and increased competition with commercial fisheries. The last record in Japan was a juvenile, captured in 1974 off the coast of Rebun Island, northern Hokkaido."
- (Japanese) "ニホンアシカ剥製標本", the ReCCLE (Research Center for Coastal Lagoon Environments) Museum, Shimane University, Japan.
- (Japanese) (en abstract available) Itoo Tetsuro, Fujita Akiyoshi, Kubo Kin-ya, "Pinniped records on the neighbouring waters of the Korean Peninsula: Japanese sea lions and larga seals recorded in the ancient literature of Korea", 野生生物保護 (Wildlife conservation Japan),Vol.6, No.2 (20010731), 51-66, Wildlife Conservation Society ISSN 13418777.
- (Japanese) "天王寺動物園で「絶滅の危機にある動物展」を開催します" Tennoji Zoo, Osaka, Japan.
- Zalophus californianus japonicus (EX), Red Data Book Tottori (mammals), Tottori Prefecture, Japan, p. 34.
- (Japanese) Zalophus californianus japonicus (EX), Shimane Red Data Book 2004, Shimane Prefecture, Japan.
- The Jomon people in the northern Island, National Museum of Japanese History.
- The Sannai Maruyama Site-Food, Aomori Prefecture, Japan, p. 7.
- (Japanese) (en abstract available) Michiko Niimi, Sea Mammal Hunting of the Jomon Culture in Hokkaido, Bulletin of the Department of Archaeology, 9 (19901228), 137-171, University of Tokyo ISSN 02873850
- Terajima Ryōan, Wakan Sansai Zue (ca. 1712), vol. 38, Amimals, p. 72, sea lion and fur seal "其肉亦不甘美 唯熬油為燈油 (the meat is not tasty and just used to render oil for oil lamps.)".
- 일본어부에 의해 멸종당한 독도 강치 (in Korean). Dokdocenter.org. 2007-03-05. Retrieved 2007-09-20.
- 독도에 바다사자 복원한다 (in Korean). The Kukmin Daily archived by Korea Coast Guard. 2006-02-02. Retrieved 2008-07-18.a) "푸른울릉·독도가꾸기모임 이예균 회장은 "일본 자료를 살펴보면 독도는 단순히 바다사자가 살던 섬이 아니라 바다사자의 최대 번식지였다"며 "일본의 다케시마어렵회사가 1905년부터 8년 동안 독도에서 1만4천여마리나 집중 포획하면서 바다사자가 멸종의 길로 접어들었다"고 말했다.", b) "50년대 독도의용수비대가 활약할 당시만 해도 20∼30마리씩 떼를 지어 독도 연안에서 서식하는장면이 목격됐다. 독도의용수비대원이던 이규현씨(82·울릉군 울릉읍 도동리)는 "당시 독도에서 강치(바다사자) 무리를 간간이 볼 수 있었고, 울릉도 주민들은 이를 가재, 강치로 부르기도 했다"고 말했다." c) "환경부 관계자는 "독도 바다사자 복원사업을 시작하려면 반드시 독도만이 아니라 동해안 전역에 바다사자를 살게 하는 쪽으로 접근할 필요가 있다"고 말했다."
- "Extinct Sea Lions to Bring Back to Korea". Korea Times. 2007-09-05. Retrieved 2007-09-06.
- "Encyclopedia of Marine Mammals second edition". Academic Press 2008. 2008. Retrieved 2011-05-23.
- The Extinction Website: Zalophus japonicus
- (Korean) "독도 바다사자(강치) 복원에 대한 조사 및 타당성 검토요청 (Request for Research on Feasibility of Reintroducing Dokdo Sea Lions)", South Korean Ministry of Environment, 2006-01-09.