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Shinisaurus crocodilurus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA REPTILIA SQUAMATA SHINISAURIDAE

Scientific Name: Shinisaurus crocodilurus
Species Authority: Ahl, 1930
Common Name(s):
English Chinese Crocodile Lizard
Taxonomic Notes: The status of Shinisauridae, erected by Ahl (1930), as a distinct, monotypic family was supported by Macey et al. (1999). Ziegler et al. (2008) determined that morphological and mitochondrial genetic differentiation among extant subpopulations was insufficient to justify the recognition of Chinese and Vietnamese subpopulations as separate taxa or subspecies, despite an apparent geographical separation of at least 500 km.

Assessment Information [top]

Red List Category & Criteria: Endangered B1ab(ii,iii,iv,v) ver 3.1
Year Published: 2014
Date Assessed: 2014-03-20
Assessor(s): Nguyen, T.Q., Hamilton, P. & Ziegler, T.
Reviewer(s): Bowles, P.
Justification:
Listed as Endangered under Criterion B on the basis that this species occurs as a severely fragmented population over an area of southern China and northern Viet Nam which, while extensive, certainly represents an extent of occurrence (excluding unsuitable habitat) below 5,000 km2, and it is subject to a continuing decline in the number of mature individuals due to harvesting, the extent and quality of its habitat due to varied forms of habitat loss, and likely in the number of locations (and so also area of occupancy) as at least one of the known subpopulations (with only 10 individuals in 2008) is almost certainly too small to be viable. Additionally, on the basis of evidence that this species has been subject to substantial population declines, and possibly local extinctions, over the 30 years between 1978 and 2008 this species is thought to have declined by an estimated 84% over 30 years (=28% over 10 years assuming a constant rate of decline); the species’ generation time is unclear but three generations are almost certainly longer than 10 years, and population declines across the species’ range are therefore believed to have exceeded 30% within three generations and may be closer to (or possibly even exceed) 50%, thus making the species close to qualifying for Endangered under Criterion A2. Research is underway to obtain demographic data for the Vietnamese subpopulation, and it is possible that further data will suggest a higher rate of decline than currently recognized.

Geographic Range [top]

Range Description: This species is endemic to China and adjacent Viet Nam. Eight subpopulations are known to be extant in China, from disjunct localities in Guangxi Province (in Guiping, Hezhou, Jinxiu, Zhaoping and Mengshan Counties) and Luokeng Nature Reserve in Guangdong (Quijang County) (Huang et al. 2008). The Chinese localities are separated from one another by distances of 10 km or more (Huang et al. 2008). The lizard may have been extirpated from five additional Chinese sites it previously occupied, and from which there are no recent reports (Huang et al. 2008). Le and Ziegler (2003) reported the species from northern Viet Nam for the first time; it is still known in this country only from the eastern and western slopes of Yen Tu Mountain (Bac Giang and Quang Ninh Provinces), over 500 km from the closest Chinese locality, and the Vietnamese subpopulation is itself thought to be fragmented. The species' elevational range is from 200-1,500 m asl.; in Viet Nam it has been recorded from a more restricted elevational band between 400-800 m asl. (Le and Ziegler 2003, Huang et al. 2008).

This highly disjunct distribution is thought to reflect a relict species, which now survives only in widely separated Pleistocene refugia. It has been estimated that as little as 456.45 km2 of suitable habitat remains within its Chinese range (Huang et al. 2008). No similar estimate of suitable habitat extent exists for Viet Nam, however, the total extent of occurrence encompassing the known sites in this country is around 1,500 km2.
Countries:
Native:
China (Guangdong, Guangxi, Hunan - Possibly Extinct); Viet Nam
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Huang et al. (2008) summarized available information to that date on subpopulation status and trends for Chinese subpopulations, included data from surveys these authors conducted of known localities. Surveys of two known localities in Guangxi recorded no evidence of surviving subpopulations, and questionnaire-based surveys of local residents (three counties in Hunan Province) found that the species had not been detected for more than 10 years at these sites. Huang et al. (2008) suggested that the species may be extinct at some or all of these localities.

The first quantitative survey on the species was carried out in 1978 (Zeng and Zhang 2004), which estimated the total known population at 6,000 individuals. Although apparently not using directly comparable methods, Huang et al. (2008) estimate a total Chinese population of 950 animals, including two sites that were not surveyed  in 1978. The largest subpopulation is estimated to contain no more than 350 individuals, the smallest as few as 10.

Due to the species’ disjunct range, its reliance on specific and patchily-distributed aquatic habitats and consequently presumably limited dispersal abilities, and because the largest Chinese subpopulation is estimated to contain approximately 36% of the overall population in this country, the global population is considered to be severely fragmented. It is unlikely to recolonize areas from which it has already been lost, or where low subpopulation sizes may result in near-future extinction. Continuing pressures exist from both habitat loss and direct hunting and so population declines are believed to be ongoing.

Age at maturity has been estimated at three years (Wang et al. 2009). Other demographic variables, such as survivorship in the wild, generation time, sex ratio, and age structure are unknown, but research is underway to collect this data for the Vietnamese subpopulation and to evaluate its current population status (Q.T. Nguyen in prep.) It is likely that the three-generation period will exceed 10 years, but no more precise value is available.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: Shinisaurus crocodilurus is found in subtropical evergreen broadleaf forests at moderate elevations (Le and Ziegler 2003, Huang et al. 2008). It is an obligate semi-aquatic species restricted to karst mountain drainages containing small streams with at least some slow stretches; in these areas it is only found in small streams and pools. These habitats are widely separated from one another by lowland forest and cultivated lands. Animals prefer thick vegetation, including trees with branches overhanging waterbodies that can be used as shelter and sleeping sites. It frequently spends hours motionless out of water and will not respond to external stimuli (www.hoglezoo.org/meet_our_animals/animal_finder/chinese_crocodile_lizard/), behaviour which may increase its susceptibility to hunting pressure.

The lizard is diurnal, being active mainly in the morning and afternoon, and semi-aquatic; it will dive into water when threatened, and can remain submerged for long periods. Water temperatures below around 15.5°C trigger hibernation between November and March, and animals will often hibernate communally in rock crevices or tree holes. The lizard is viviparous, with gestation of about nine months, with a litter produced yearly (Zhang 2002). The litter consists of 2-12 young.
Systems: Terrestrial; Freshwater

Use and Trade [top]

Use and Trade: This species has been collected for the pet trade; a total of 642 individuals were reported in CITES exports between 1990 and 2012, with a peak in 2005 when 200 animals were recorded in exports from each of Thailand and Japan (presumably re-exports, as the species is not native to either country). The most recent recorded exports are from 2012, with a total of 17 individuals; in every other year except 2005 33 or fewer animals were recorded in trade, with no consistent trend. The species is, however, thought to be collected for illegal trade in higher volumes; a survey of local villagers in Chinese villages near Shinisaurus habitats found that 54 of 75 (72%) men surveyed hunted the lizard. Twenty one of 75 (28%) hunted the lizard “frequently” (Huang et al. 2008). At the time of the survey, one animal would sell for between 10 and 1,000 RMB (up to $164 USD). More recently, prices have increased to $800-1,500 in the US market (P. Hamilton pers. obs.), but CITES documentation suggests that very few animals are captive-bred. Two hundred RMB is equivalent to two months’ salary in the surveyed areas, so the economic incentive to exploit the species is high (Huang et al. 2008).

The species is traditionally believed to act as a cure for insomnia, and the collection and consumption of the species for use in traditional medicine has likely been ongoing for centuries; with additional, novel pressures on the lizard and apparently small surviving populations this activity is now likely to threaten its survival.

At tourist sites in Viet Nam, some individuals were sold at tourist sites for 10-20 USD (Yen Tu Temple in Quang Ninh Province; Q.T. Nguyen, pers. obs.; Le and Ziegler 2003). The species also appears to be used for food and medicine in small numbers in this area.

Threats [top]

Major Threat(s): This species is threatened by habitat loss and by harvesting, mainly illegal hunting for the international pet trade. Logging at Chinese localities both removes perch sites and suitable ground cover and leads to desiccation of stream habitats. Electro-fishing and poisoning are frequently used to catch fish in southern China, and as a largely aquatic species animals – particularly juveniles – are susceptible to being killed by this practice. Additional pressures exist from agro-forestry, small-scale dam construction and mining activities. Only three of the Chinese localities lie within nature reserves (Huang et al. 2008); while the habitat in these areas is well-protected, illegal hunting still takes place occasionally; outside protected areas the habitat is severely degraded and illegal trade appears to be frequent, with illegal domestic trade in the species being common in cities around the species’ known localities.

In Viet Nam, forest on both sides of Yen Tu Mountain is divided into isolated fragments as a result of road-building and associated tourist infrastructure; while the lizard is found within protected areas in Viet Nam its habitat is at risk from agricultural encroachment (and associated fires), illegal timber logging and water pollution around tourist sites. Localized coal mining occurs close to two streams where the species has been found, and is leading to forest clearance and degradation in the surrounding area.

Conservation Actions [top]

Conservation Actions: While this species is found in several protected areas, at least 50% of the known localities (including the one believed to contain the largest subpopulation – Huang et al. 2008) are outside protected areas and improved enforcement (including specific training of reserve staff focused on protecting this species) is required to prevent illegal harvesting and encroachment into the existing reserves. The species is listed on CITES Appendix II; although the major pressures from trade are currently thought to be from illegal harvesting and from domestic use rather than from legal export regulated by CITES, it has been proposed that the species may warrant listing on Appendix I (Q.T. Nguyen and P. Hamilton pers. comms.) Ex situ conservation should be considered, with a plan for captive breeding and eventual reintroduction. National legislation has been proposed to list this as a protected species in Viet Nam.

Citation: Nguyen, T.Q., Hamilton, P. & Ziegler, T. 2014. Shinisaurus crocodilurus. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 22 December 2014.
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