Chinese water dragon: Difference between revisions
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==Threats and conservation== |
==Threats and conservation== |
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Though locally abundant in some areas, the Chinese water dragon faces persistent threats and a steadily declining wild population. The IUCN has rated it as a [[Vulnerable species]] since 2017.<ref name=":4">{{Cite web |last=Stuart, B., Sumontha, M., Cota, M., Panitvong, N., Nguyen, T.Q., Chan-Ard, T., Neang, T., Rao, D.-q. & Yang, J. |date=2019 |title=''Physignathus cocincinus'' |url=https://www.iucnredlist.org/species/104677699/104677832 |website=The IUCN Red List of Threatened Species |doi=10.2305/IUCN.UK.201}}</ref> In accordance with a 2022 proposal,<ref>{{Cite web |date=November 2022 |title=CoP19 Prop. 14 |url=https://cites.org/sites/default/files/documents/E-CoP19-Prop-14.pdf |website=CONVENTION ON INTERNATIONAL TRADE IN ENDANGERED SPECIES OF WILD FAUNA AND FLORA, Nineteenth meeting of the Conference of the Parties}}</ref> the Chinese water dragon has been listed on [[CITES Appendix II]] (requiring a CITES-approved permit for export) since 2023. |
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Though common in some parts of its range, the Chinese water dragon faces persistent threats and a steadily declining wild population. The IUCN has rated it as a [[Vulnerable species]] since 2017. |
|||
=== Population dynamics === |
=== Population dynamics === |
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At one site in Cambodia the species experienced a 50% population decline in 18 years, while a 2007 estimate considered the entire Vietnamese population to have declined by 20% over the previous decade. |
At one site in Cambodia the species experienced a 50% population decline in 18 years, while a 2007 estimate considered the entire Vietnamese population to have declined by 20% over the previous decade. Based on these estimates, the species as a whole may be declining by 30% every 18 years.<ref name=":4" /> |
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A 2017 population survey in [[Thừa Thiên Huế province|Thua Thien Hue Province]], Vietnam estimated that up to 250 individuals in total were present at the 11 sampled sites (combined). This is far below the several thousand expected to sustain long-term genetic diversity for a species restrained to narrow riparian habitats. Sites sampled in June 2017 show a slightly lower population and a higher relative proportion of females and sub-adults relative to the same sites in April 2017. Adults were uncommon in both months while juveniles were most common in April, maturing into a large sub-adult cohort by June. Chinese water dragons in Thua Thien Hue occur at moderate to high densities, up to 2.6 per 100 meters in April 2017.<ref name=":1" /> |
A 2017 population survey in [[Thừa Thiên Huế province|Thua Thien Hue Province]], Vietnam estimated that up to 250 individuals in total were present at the 11 sampled sites (combined). This is far below the several thousand expected to sustain long-term genetic diversity for a species restrained to narrow riparian habitats. Sites sampled in June 2017 show a slightly lower population and a higher relative proportion of females and sub-adults relative to the same sites in April 2017. Adults were uncommon in both months while juveniles were most common in April, maturing into a large sub-adult cohort by June. Chinese water dragons in Thua Thien Hue occur at moderate to high densities, up to 2.6 per 100 meters in April 2017.<ref name=":1" /> |
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Somewhat different patterns were observed in a 2014–2016 survey in Northern Vietnam. In disturbed areas, Chinese water dragons occur at very low densities (as low as 0.17 per 100 meters in 2015), and adults make up to a third of the population. Several previously reported populations were probably [[extirpated]], as individuals could not be found at 8 of the 15 investigated stream transects.<ref name=":3">{{Cite journal |last=Gewiss |first=Laurenz Rafael |last2=Ngo |first2=Hai Ngoc |last3=van Schingen-Khan |first3=Mona |last4=Bernardes |first4=Marta |last5=Rauhaus |first5=Anna |last6=Pham |first6=Cuong The |last7=Nguyen |first7=Truong Quang |last8=Ziegler |first8=Thomas |date=2020-09-01 |title=Population assessment and impact of trade on the Asian Water Dragon (Physignathus cocincinus Cuvier, 1829) in Vietnam |url=https://www.sciencedirect.com/science/article/pii/S2351989420307344 |journal=Global Ecology and Conservation |language=en |volume=23 |pages=e01193 |doi=10.1016/j.gecco.2020.e01193 |issn=2351-9894}}</ref> |
Somewhat different patterns were observed in a 2014–2016 survey in [[Northern Vietnam]]. In disturbed areas, Chinese water dragons occur at very low densities (as low as 0.17 per 100 meters in 2015), and adults make up to a third of the population. Several previously reported populations were probably [[extirpated]], as individuals could not be found at 8 of the 15 investigated stream transects.<ref name=":3">{{Cite journal |last=Gewiss |first=Laurenz Rafael |last2=Ngo |first2=Hai Ngoc |last3=van Schingen-Khan |first3=Mona |last4=Bernardes |first4=Marta |last5=Rauhaus |first5=Anna |last6=Pham |first6=Cuong The |last7=Nguyen |first7=Truong Quang |last8=Ziegler |first8=Thomas |date=2020-09-01 |title=Population assessment and impact of trade on the Asian Water Dragon (Physignathus cocincinus Cuvier, 1829) in Vietnam |url=https://www.sciencedirect.com/science/article/pii/S2351989420307344 |journal=Global Ecology and Conservation |language=en |volume=23 |pages=e01193 |doi=10.1016/j.gecco.2020.e01193 |issn=2351-9894}}</ref> |
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=== |
=== Hunting and the pet trade === |
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The most severe threat to the species is harvesting for meat and the [[pet trade]]. According to a series of 2016 interviews with 21 rural hunter groups, water dragons are frequent and easy |
The most severe threat to the species is harvesting for meat and the [[pet trade]]. According to a series of 2016 interviews with 21 rural hunter groups, water dragons are a frequent and easy target of traps and hand collecting throughout Thua Thien Hue. Hunting pressure is greatest in May and June, with adult males prioritized due to their large size and conspicuous appearance. This agrees with the decreasing proportion of adult males found in June compared to April. Water dragon meat is typically sold to local restaurants, while eggs are stored in alcohol to be used as [[traditional medicine]].<ref name=":1" /> Skins and leather are also traded and exported.<ref name=":4" /> |
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Wild water dragons are captured and sold as pets on social media platforms for both Vietnamese customers and the international markets of Europe and the United States.<ref name=":1" /> In Vietnam, about five times as many Chinese water dragons are sold for meat compared to those sold as pets. From 2010 to 2018, a stable average of around 7,000 live Chinese water dragons per year were exported to the [[European Union]]. About 89% came from Vietnam, though information on their production (wild caught or captive bred) is |
Wild water dragons are captured and sold as pets on social media platforms for both Vietnamese customers and the international markets of Europe and the United States.<ref name=":1" /> In Vietnam, about five times as many Chinese water dragons are sold for meat compared to those sold as pets. From 2010 to 2018, a stable average of around 7,000 live Chinese water dragons per year were exported to the [[European Union]]. About 89% came from Vietnam, though information on their production (wild caught or captive bred) is available for fewer than 13% of recorded exports to Europe. Exports to the United States are even higher despite recent declines: an average of 81,000 per year from 2002 to 2011, and around 48,000 per year from 2013 to 2017. Practically all water dragons exported to the United States are Vietnamese in origin. At least 95% are wild caught while around 3% are reportedly captive bred in Vietnam.<ref name=":3" /> Captive breeding may be a viable conservation strategy; Chinese water dragons breed readily in captivity, though not at a fast enough rate to counteract their ease of capture.<ref name=":4" /> |
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=== Habitat loss === |
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A smaller threat, though still impactful, is degradation or removal of the forested stream habitats which water dragons rely on. In Thua Thien Hue, illegal logging and a major highway construction project are likely partially responsible for losses in the [[Nam Đông district|Nam Dong]] and [[A Lưới district|A Luoi]] districts. These pressures are less prevalent in the uplands of [[Phong Điền district, Thừa Thiên Huế|Phong Dien district]], which seems to not experience the same degree of population decline.<ref name=":1" /> Logging and expansion of agricultural and tourism infrastructure also contribute to the paucity of suitable habitats in Northern Vietnam. Coal mining and stream pollution may also threaten the species, as reported for ecologically similar reptiles in the region, such as the [[Chinese crocodile lizard]] (''Shinisaurus crocodilurus'').<ref name=":3" /> |
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Despite its common name, the Chinese water dragon is exceedingly rare in China, where it is threatened by dam construction on top of the same pressures as the Vietnamese populations. Suitably undeveloped habitats are uncommon in Cambodia and Laos. Conversely, water dragons in Thailand occur almost exclusively within [[Protected area|protected areas]].<ref name=":4" /> |
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==Gallery== |
==Gallery== |
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<gallery> |
<gallery> |
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Chinese Water Dragon (Physignathus cocincinus) - Khao Yai National Park - 2.jpg| |
Chinese Water Dragon (Physignathus cocincinus) - Khao Yai National Park - 2.jpg|Detailed view of the head - [[Khao Yai National Park]], Thailand |
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Chinese Water Dragon (Physignathus cocincinus) - Khao Yai National Park - 3.jpg| |
Chinese Water Dragon (Physignathus cocincinus) - Khao Yai National Park - 3.jpg|Khao Yai National Park, Thailand |
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Physignathus cocincinus chinese green water dragon toronto zoo jan 08 1.jpg|Detailed view of legs and scales |
Physignathus cocincinus chinese green water dragon toronto zoo jan 08 1.jpg|Detailed view of legs and scales |
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Physignathus cocincinus chinese green water dragon toronto zoo jan 08 2.jpg|Detailed view of head |
Physignathus cocincinus chinese green water dragon toronto zoo jan 08 2.jpg|Detailed view of the head |
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</gallery> |
</gallery> |
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Revision as of 03:40, 6 July 2023
| Chinese water dragon | |
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Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Iguania |
| Family: | Agamidae |
| Genus: | Physignathus Cuvier, 1829 |
| Species: | P. cocincinus
|
| Binomial name | |
| Physignathus cocincinus Cuvier, 1829
| |
Physignathus cocincinus is a species of agamid lizard native to southern China and mainland Southeast Asia.[2] It is commonly known as the Chinese water dragon, Asian water dragon, Thai water dragon, or green water dragon.[3]
Taxonomy
The species and genus were first described by Georges Cuvier in 1829.[4] The epithet cocincinus is from the French term Cocincine, for the type locality Cochin-china (Vietnam). Physignathus means 'inflated jaw'.
During the 19th and 20th centuries, several other species of agamid lizards were placed in Cuvier's genus Physignathus. These have been reclassified into separate genera, leaving Physignathus with only the original species P. cocincinus remaining. For example, the Australian water dragon (Intellagama lesueurii) was formerly P. lesueurii.
Description
Chinese water dragons can grow up to 36" (0.9m) in total length, including tail, and can live from 10 to 15 years.[5]
Coloration ranges from dark to light green, or sometimes purple with an orange stomach. Diagonal stripes of green or turquoise are found on the body, while the tail is banded from the middle to the end with green and white. Their undersides range from white, off white, very pale green, or pale yellow. But their throats are considered to be more attractive, which can be quite colorful (blue and purple, or peach), some with a single color, some with stripes. Adult males have larger, more triangular heads than females, and develop larger crests on the head, neck and tail, and are larger in general. The tail, slightly over two-thirds of the entire body length, can be used as a weapon, for balance, and to assist swimming.[6]
Like many other reptiles the Chinese water dragon possesses a small, iridescent, photosensitive spot between their eyes referred to as the pineal eye (or parietal eye, or colloquially as the third eye) that is thought to help thermoregulate their bodies by sensing differences in light to assist with basking and seeking shelter after sunset.[7] Since it recognizes differences in light, the parietal eye can also help the lizard avoid predation from birds and other aerial threats, and can awaken from deep sleep from even slight changes in light from overhead. These animals are very docile and allow physical activity.
Habitat and behavior
Chinese water dragons are native to the lowland and highland forests of southern China (Guangdong, Guangxi, and Yunnan provinces) and Southeast Asia (Vietnam, Laos, Cambodia, eastern Thailand, and reportedly Myanmar).[8] Chinese water dragons are most commonly found within dense closed forest along the banks of freshwater lakes and streams.[6] Water dragons live in areas with average humidity levels of 40–80% and temperatures ranging from 80–90 °F (26–32 °C).
They are active during the day (diurnal), and spend most of their time in the trees or plants (arboreal). If threatened, the dragon will drop from the trees into the water and either swim to safety or remain submerged for up to 90 minutes.
Chinese water dragons have established themselves in Hong Kong, probably from released pet animals.[9]
Diet
Though they will also eat vegetation, the diet of the water dragon consists mainly of insects, supplemented with an occasional small fish, mammal, bird, reptile or egg.[3] Mollusks and small crustaceans are also part of their diet.[10]
Reproduction
Though Chinese water dragons reproduce sexually in the wild, there is one reported case of facultative parthenogenesis in a captive individual.[11][12] A female housed at the Smithsonian National Zoo produced viable offspring in 2016 and 2018, along with numerous unfertilized and nonviable eggs. The two surviving offspring are homozygous or hemizygous at seven particular microsatellite loci in the genome. This condition would be nearly impossible if sexual reproduction was involved, since at least a few of the seven microsatellite loci would be expected to be heterozygous. Physignathus cocincinus is the only agamid known to reproduce via parthenogenesis, though the low hatch rate suggests that this is an accidental occurrence rather than an ingrained evolutionary strategy.[11]
Threats and conservation
Though locally abundant in some areas, the Chinese water dragon faces persistent threats and a steadily declining wild population. The IUCN has rated it as a Vulnerable species since 2017.[13] In accordance with a 2022 proposal,[14] the Chinese water dragon has been listed on CITES Appendix II (requiring a CITES-approved permit for export) since 2023.
Population dynamics
At one site in Cambodia the species experienced a 50% population decline in 18 years, while a 2007 estimate considered the entire Vietnamese population to have declined by 20% over the previous decade. Based on these estimates, the species as a whole may be declining by 30% every 18 years.[13]
A 2017 population survey in Thua Thien Hue Province, Vietnam estimated that up to 250 individuals in total were present at the 11 sampled sites (combined). This is far below the several thousand expected to sustain long-term genetic diversity for a species restrained to narrow riparian habitats. Sites sampled in June 2017 show a slightly lower population and a higher relative proportion of females and sub-adults relative to the same sites in April 2017. Adults were uncommon in both months while juveniles were most common in April, maturing into a large sub-adult cohort by June. Chinese water dragons in Thua Thien Hue occur at moderate to high densities, up to 2.6 per 100 meters in April 2017.[8]
Somewhat different patterns were observed in a 2014–2016 survey in Northern Vietnam. In disturbed areas, Chinese water dragons occur at very low densities (as low as 0.17 per 100 meters in 2015), and adults make up to a third of the population. Several previously reported populations were probably extirpated, as individuals could not be found at 8 of the 15 investigated stream transects.[15]
Hunting and the pet trade
The most severe threat to the species is harvesting for meat and the pet trade. According to a series of 2016 interviews with 21 rural hunter groups, water dragons are a frequent and easy target of traps and hand collecting throughout Thua Thien Hue. Hunting pressure is greatest in May and June, with adult males prioritized due to their large size and conspicuous appearance. This agrees with the decreasing proportion of adult males found in June compared to April. Water dragon meat is typically sold to local restaurants, while eggs are stored in alcohol to be used as traditional medicine.[8] Skins and leather are also traded and exported.[13]
Wild water dragons are captured and sold as pets on social media platforms for both Vietnamese customers and the international markets of Europe and the United States.[8] In Vietnam, about five times as many Chinese water dragons are sold for meat compared to those sold as pets. From 2010 to 2018, a stable average of around 7,000 live Chinese water dragons per year were exported to the European Union. About 89% came from Vietnam, though information on their production (wild caught or captive bred) is available for fewer than 13% of recorded exports to Europe. Exports to the United States are even higher despite recent declines: an average of 81,000 per year from 2002 to 2011, and around 48,000 per year from 2013 to 2017. Practically all water dragons exported to the United States are Vietnamese in origin. At least 95% are wild caught while around 3% are reportedly captive bred in Vietnam.[15] Captive breeding may be a viable conservation strategy; Chinese water dragons breed readily in captivity, though not at a fast enough rate to counteract their ease of capture.[13]
Habitat loss
A smaller threat, though still impactful, is degradation or removal of the forested stream habitats which water dragons rely on. In Thua Thien Hue, illegal logging and a major highway construction project are likely partially responsible for losses in the Nam Dong and A Luoi districts. These pressures are less prevalent in the uplands of Phong Dien district, which seems to not experience the same degree of population decline.[8] Logging and expansion of agricultural and tourism infrastructure also contribute to the paucity of suitable habitats in Northern Vietnam. Coal mining and stream pollution may also threaten the species, as reported for ecologically similar reptiles in the region, such as the Chinese crocodile lizard (Shinisaurus crocodilurus).[15]
Despite its common name, the Chinese water dragon is exceedingly rare in China, where it is threatened by dam construction on top of the same pressures as the Vietnamese populations. Suitably undeveloped habitats are uncommon in Cambodia and Laos. Conversely, water dragons in Thailand occur almost exclusively within protected areas.[13]
Gallery
-
Detailed view of the head - Khao Yai National Park, Thailand -
Khao Yai National Park, Thailand -
Detailed view of legs and scales -
Detailed view of the head
_-_Khao_Yai_National_Park_-_2.jpg)
_-_Khao_Yai_National_Park_-_3.jpg)
References
- ^ "Appendices | CITES". cites.org. Retrieved 2023-03-01.
- ^ "Chinese Water Dragon (Physignathus cocincinus)". iNaturalist. Retrieved 2022-01-18.
- ^ a b "Asian water dragon". Smithsonian's National Zoo & Conservation Biology Institute. 8 September 2017.
- ^ Cuvier, M. [Georges] le Baron (1829). Le règne animal distribué d'après son organisation, pour servir de base à l'histoire naturelle des animaux et d'introduction à l'anatomie comparée. Tome 2 (in French) (2 ed.). Déterville et Crochard. p. 41.
- ^ Healey, Mariah. "Chinese Water Dragon Care Sheet". ReptiFiles. Archived from the original on 2022-01-18. Retrieved 2022-01-18.
- ^ a b "Chinese Water Dragon". World Association of Zoos and Aquariums. Archived from the original on 3 January 2015. Retrieved 18 August 2012.
- ^ "Reptiles & Amphibians Facts Sheets: Chinese Water Dragon". National Zoological Park. Archived from the original on 2008-10-07. Retrieved 2008-10-22.
- ^ a b c d e Nguyen, Truong Quang; Ngo, Hai Ngoc; Pham, Cuong The; Van, Hoang Nguyen; Ngo, Chung Dac; Schingen, Mona van; Ziegler, Thomas (2018-03-15). "First population assessment of the Asian Water Dragon (Physignathus cocincinus Cuvier, 1829) in Thua Thien Hue Province, Vietnam". Nature Conservation. 26: 1–14. doi:10.3897/natureconservation.26.21818. ISSN 1314-3301.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ To, Allen (2005). "Another alien has landed: the discovery of a wild population of water dragon, Physignathus cocincinus, in Hong Kong" (PDF). Porcupine. 33 (November): 3–4.
- ^ "Water Dragon".
- ^ a b Miller, Kyle L.; Rico, Susette Castañeda; Muletz-Wolz, Carly R.; Campana, Michael G.; McInerney, Nancy; Augustine, Lauren; Frere, Celine; Peters, Alan M.; Fleischer, Robert C. (2019-06-05). "Parthenogenesis in a captive Asian water dragon (Physignathus cocincinus) identified with novel microsatellites". PLOS ONE. 14 (6): e0217489. doi:10.1371/journal.pone.0217489. ISSN 1932-6203. PMC 6550409. PMID 31166974.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ^ Burns, Mercedes (Dec 26, 2020). "Parthenogenesis: How females from some species can reproduce without males". Ars Technica. Retrieved Jan 10, 2021.
- ^ a b c d e Stuart, B., Sumontha, M., Cota, M., Panitvong, N., Nguyen, T.Q., Chan-Ard, T., Neang, T., Rao, D.-q. & Yang, J. (2019). "Physignathus cocincinus". The IUCN Red List of Threatened Species. doi:10.2305/IUCN.UK.201.
{{cite web}}: CS1 maint: multiple names: authors list (link) - ^ "CoP19 Prop. 14" (PDF). CONVENTION ON INTERNATIONAL TRADE IN ENDANGERED SPECIES OF WILD FAUNA AND FLORA, Nineteenth meeting of the Conference of the Parties. November 2022.
- ^ a b c Gewiss, Laurenz Rafael; Ngo, Hai Ngoc; van Schingen-Khan, Mona; Bernardes, Marta; Rauhaus, Anna; Pham, Cuong The; Nguyen, Truong Quang; Ziegler, Thomas (2020-09-01). "Population assessment and impact of trade on the Asian Water Dragon (Physignathus cocincinus Cuvier, 1829) in Vietnam". Global Ecology and Conservation. 23: e01193. doi:10.1016/j.gecco.2020.e01193. ISSN 2351-9894.
External links
| Authority control databases: National |
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