Opisthotropis kikuzatoi 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Squamata Natricidae

Scientific Name: Opisthotropis kikuzatoi (Okada & Takara, 1958)
Common Name(s):
English Kikuzato’s Stream Snake, Kikuzato's Brook Snake
Liopeltis kikuzatoi Okada & Takara, 1958

Assessment Information [top]

Red List Category & Criteria: Critically Endangered B1ab(iii,v)+2ab(iii,v) ver 3.1
Year Published: 2017
Date Assessed: 2016-12-03
Assessor(s): Kidera, N. & Ota, H.
Reviewer(s): Bowles, P.

Opisthotropics kikuzatoi is endemic to Kumejima Island. The area of occupancy is estimated to be less than 10 km2, there is an ongoing decline in the extent and quality of its habitat and in the number of mature individuals. This species occurs as two completely isolated subpopulations, at least one of which is unlikely to be viable and shows some evidence of genetic problems, and is considered to occur as a severely fragmented population. The species is listed as Critically Endangered. 

Previously published Red List assessments:

Geographic Range [top]

Range Description:

Opisthotropis kikuzatoi is endemic to Kumejima Island, one of the Okinawa Group islands in Japan. Its distribution is restricted to two hilly areas located in the northern and the southern parts of the Island. The total area of occupancy is approximately 10 km2. The intervening area has been completely converted to cultivated lands and residential areas (Ota 2014).

Countries occurrence:
Japan (Nansei-shoto)
Additional data:
Estimated area of occupancy (AOO) - km2:9.9
Number of Locations:2Continuing decline in number of locations:Unknown
Range Map:Click here to open the map viewer and explore range.

Population [top]


This is a rare species. The frequency of occurrence has dropped to one tenth in fifteen years after 1983 in one of the two localities (Ota 2014). There is no information on the status of the other subpopulation (Ota 2014), but it is presumably in decline.

Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Extreme fluctuations:UnknownPopulation severely fragmented:Yes

Habitat and Ecology [top]

Habitat and Ecology:

This species occurs in permanent streams along broadleaved evergreen forests. Its habitat is a highly specific environment which experiences no drought, offers sufficient food resources such as freshwater crabs and shade vegetation to avoiding direct sunlight (Ota 2014). This habitat remains only in a very restricted part of Kumejima.

Systems:Terrestrial; Freshwater
Continuing decline in area, extent and/or quality of habitat:Yes
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: There is no information on any use of or trade in this species.

Threats [top]

Major Threat(s):

The major threats are water pollution, incidental capture as bycatch, and predation by introduced bull frog. The cause of water pollution is unclear. The bullfrog (Lithobates catesbeianus) has been introduced to Kumejima Island in 1953; this may result in high predation pressure to which this snake may be especially sensitive following drastic declines over the last 15 years. It is likely that the population is undergoing a decline of genetic diversity due to inbreeding, as the two subpopulations are completely isolated from one another and at least one now appears to be very small. Individuals with asymmetrical scales on their heads are often observed (Ota 2014).

Conservation Actions [top]

Conservation Actions:

Opisthotropis kikuzatoi is categorized as a National Endangered Species of Wild Fauna and Flora under the Act on Conservation of Endangered Species of Wild Fauna and Flora, as well as a natural monument in Okinawa. Capture is forbidden. The middle and northern area in the island was assigned as Natural Habitat Protection Area by Environment Agency of Japan in 1998 (Ota 2014).

Classifications [top]

1. Forest -> 1.6. Forest - Subtropical/Tropical Moist Lowland
suitability:Suitable season:resident major importance:Yes
5. Wetlands (inland) -> 5.1. Wetlands (inland) - Permanent Rivers/Streams/Creeks (includes waterfalls)
suitability:Suitable season:resident major importance:Yes
2. Land/water management -> 2.1. Site/area management
2. Land/water management -> 2.2. Invasive/problematic species control

In-Place Research, Monitoring and Planning
  Action Recovery plan:No
  Systematic monitoring scheme:No
In-Place Land/Water Protection and Management
  Occur in at least one PA:Unknown
  Area based regional management plan:Yes
In-Place Species Management
In-Place Education
5. Biological resource use -> 5.4. Fishing & harvesting aquatic resources -> 5.4.3. Unintentional effects: (subsistence/small scale) [harvest]
♦ timing:Ongoing ♦ scope:Whole (>90%) ♦ severity:Unknown ⇒ Impact score:Unknown 
→ Stresses
  • 2. Species Stresses -> 2.1. Species mortality

8. Invasive and other problematic species, genes & diseases -> 8.1. Invasive non-native/alien species/diseases -> 8.1.2. Named species [ Lithobates catesbeianus ]
♦ timing:Ongoing ♦ scope:Whole (>90%) ♦ severity:Unknown ⇒ Impact score:Unknown 
→ Stresses
  • 2. Species Stresses -> 2.1. Species mortality

9. Pollution -> 9.3. Agricultural & forestry effluents -> 9.3.4. Type Unknown/Unrecorded
♦ timing:Ongoing ♦ scope:Whole (>90%) ♦ severity:Unknown ⇒ Impact score:Unknown 
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation

Bibliography [top]

IUCN. 2017. The IUCN Red List of Threatened Species. Version 2017-3. Available at: (Accessed: 5 December 2017).

Ota, H. 2014. Kikuzato’s brook snake. In: Ministry of Environment (ed.), Red Data Book 2014.-Threatened Wildlife of Japan -: Reptilia /Amphibia, GYOSEI Corporation, Tokyo.

Citation: Kidera, N. & Ota, H. 2017. Opisthotropis kikuzatoi. The IUCN Red List of Threatened Species 2017: e.T15391A96877390. . Downloaded on 21 September 2018.
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