Chinese alligator

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Chinese alligator
Temporal range: Pliocene – recent
↓
[1]
At the Cincinnati Zoo and Botanical Garden
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Archosauriformes
Order: Crocodilia
Family: Alligatoridae
Genus: Alligator
Species:
A. sinensis
Binomial name
Alligator sinensis
(Fauvel, 1879)
Synonyms

The Chinese alligator (Alligator sinensis) (simplified Chinese: 扬子鳄; traditional Chinese: 揚子鱷, yáng zǐ è), also known as the Yangtze alligator,[4] China alligator,[2] or historically called the muddy dragon,[5] is a critically endangered crocodilian endemic to China. The American alligator and it are the two living species of Alligator, a genus in the family Alligatoridae.

Dark gray or black in color with a fully armored body, the Chinese alligator is less than half the size of its American relative. It brumates in self-constructed burrows in the winter and becomes nocturnal in the summer. It mates during the early summer, and its eggs are smaller than any other crocodilian. Females mature after 4-7 years, and the species typically lives to age 50, although some captive specimens have reached age 70. It primarily eats fish and invertebrates, such as mollusks and crustaceans. A vocal species, adults bellow during the mating season and young vocalize to communicate with their parents and other juveniles.

Living mostly in scattered small freshwater bodies, the Chinese alligator's distribution range is restricted to six very small regions in Anhui as of 2015. Originally living in Japan, the species previously had a wide range and population, but beginning in 5000 BC, a number of threats, such as habitat destruction, have caused the species' population and range to decline. By 1999, the population in the wild was about 150 according to the Wildlife Conservation Society, its range limited to a very small part of the land along the Yangtze River, and was between 136 and 173 in 2015. Listed as critically endangered by the International Union for Conservation of Nature, multiple conservation actions have been taking place for this species. In particular, several breeding facilities, both in China and foreign countries, have been successful with increasing the population of the alligator by breeding specimens in captivity and later releasing them into the wild, the largest of these facilities being the Anhui Research Center for Chinese Alligator Reproduction and the Changxing Nature Reserve and Breeding Center for Chinese Alligators.

Description

Comparison of the American alligator (top) and the Chinese alligator (bottom)
Detail of head

While the Chinese alligator's appearance is very similar to the only other living member of the genus, the American alligator (Alligator mississippiensis), a few differences exist.[6] One of the smallest species of crocodilians,[5] this species attains an adult length of 1.5 m (5 ft) and a mass of 36 kg (80 lb), with some exceptionally large males having reached 2.1 m (7 ft) in length and 45 kg (100 lb) in weight.[7] Females are roughly 3/4 the length of males.[8] Reports are known of alligators in China reaching 3.0 m (10 ft) in past centuries, but these are now generally considered apocryphal.[7] The species is less than half the size of the American alligator, which typically grows to a length of 3.4 m (11.2 ft) for males and 2.5 m (8.2 ft) for females.[9]

The Chinese alligator can be black or dark gray in color. Juveniles have light speckles on their body and head, while the coloring of adults is almost completely uniform.[8] The alligator has a short and broad snout,[10] which vaguely points upwards and narrows at the end. Its head is robust, more so than that of the American alligator,[11] and has a bony septum dividing its nostrils.[10] Unlike the American alligator, the Chinese alligator is fully armored,[5] including its belly.[6] It contains up to 17 rows of scales across its body, which are soft on its belly and the side of its body, while rougher on its back. Its upper eyelids have bony plates on them, a feature not present in the American alligator.[12] Its tail is wider than that of the American alligator[10] and has a ridge-like formation at the end of it where its scales intersect.[12] It does not have webbed feet, in contrast to the American alligator, which has extensive webbing on its toes.[10]

Behavior

The Chinese alligator is dormant in burrows during the winter. After its dormancy, it frequently spends time in the sun before summer begins.[11] Beginning in June and throughout the rest of summer, it becomes nocturnal, feeding in the nighttime and sheltering in the daytime, to avoid both humans and the summer heat.[6] This uncommunicative behavior gives it the ability to live in areas where humans are common.[2] A docile species, it does not intentionally hurt humans outside of potential extreme circumstances.[5]

Burrowing

The Chinese alligator brumates[11] in its burrows from late October to mid-April, emerging in early May. It constructs these burrows next to ponds and other small bodies of water, using its head and front legs to dig into the ground.[8] These burrows can be large and complex, containing a number of rooms, water pools, and entrances.[6] Most of them are 10–25 metres (33–82 ft) long, with each room containing enough space for alligators to turn around after entering. Outside of winter, they serve as retreat sites for the alligators[8] and in the summer are where the alligators take shelter in the daytime.[6] The burrows can be problematic for farmers, as they cause drainage problems in fields.[12]

Lifecycle

A baby Chinese alligator on a mass of vegetation in a body of water

The breeding season of the Chinese alligator is the early summer.[6] Once mating groups have gathered, each male Chinese alligator may impregnate one female per season.[13] During the time of mating, both male and female specimens are often aggressive to each other.[6] The rate of mating is the highest in the middle of June; during this time, males commonly search around many ponds to find a mate.[8] Nests are always built near water sources, and if possible, on islands so that they disturbed less often by people. Constructed by the females, they are composed of rotting plants, such as leaves, and have a height of 40–70 cm (16–28 in).[14] They are typically built about two to three weeks after mating,[6] during the later part of the summer, from as early as July to as late as the end of August.[2] Generally laid at night,[15] mating typically produces 20–30 eggs,[16] although according to the International Union for Conservation of Nature (IUCN), the alligator has the capability to lay 10–40 eggs.[2] After the eggs are laid, the females sometimes leave the nest, but other times stay and protect the eggs.[15] The eggs are about 6 cm (2.4 in) in length, 3.5 cm (1.4 in) in diameter, and 45 g (1.6 oz) in weight, making them smaller than the eggs of any other crocodilian.[16] Hatching in September, the temperature of egg incubation controls whether a young alligator will be male or female, a feature present in all crocodilians.[14] Mothers assist the hatching of young and help them leave the nest and bring them to the water after hatching.[11]

Young alligators when first hatched, like their eggs, are the smallest of any crocodilian, with a length of 20–22 cm (7.9–8.7 in) and weight of 25–30 g (0.88–1.06 oz). They grow very little their first year, due to being able to feed for only about 2 months after hatching before the winter comes. They depend on their mothers to protect them during their first winter, as their small size makes them an easy prey target.[17] According to the National Zoological Park, females reach maturity roughly 4-5 years after birth,[6] although other sources estimate that they mature at age six to seven.[14] A lifespan of 50 years is typical in the wild, but some specimens in captivity have lived to be 70 years old. It is able to breed in its 50s, although it cannot when any older.[18]

Feeding

The Chinese alligator is an opportunistic feeder, meaning that it can prey on a variety of different animals depending on what is available. It is a carnivore, mostly eating fish and invertebrates, such as crustaceans, insects, and snails, and when possible, it will eat rodents and aquatic birds, as well.[6] Similarly, its American relative preys on birds, fish, frogs, mammals, and invertebrates, such as snails.[9] The Chinese alligator has dull teeth, which allow it to eat prey with shells more easily.[5] A detailed study of the alligator's diet in 1985 showed that snails were by far the most common animal in its diet at 63%, with 41% of its total diet being river snails and 22% spiral-shelled snails. According to the survey, its diet also contained 16% rabbits, 8.3% mollusks, and 4.1% shrimp, with the remaining 6.8% being frogs, fish, and insects.[14]

Vocalization

The Chinese alligator is a very vocal species, making a number of different sounds in multiple situations.[16] Both sexes participate in bellowing choruses during the mating season as adults. Lasting an average of 10 minutes, the alligators remain still for the entirety of the chorus, with both sexes responding equally in rough unison. It has been theorized that this occurs as a way for mating groups to gather together rather than a mating competition,[19] although it has also been theorized that these choruses do not serve any purpose.[13] Young Chinese alligators will often communicate with each other and their parents using vocal signals, to "maintain group cohesion."[16] Young will also make sounds when in danger, which alert adults to help and caution other young nearby of the threat. Embryos produce distinctive sounds when inside their egg, which alerts the adult female that the nest is ready to be opened. These vocalizations are high-pitched, while their danger calls are louder.[16]

Distribution and habitat

The Chinese alligator lives in bodies of freshwater in subtropical and warm temperate climates.[2] Occurring at the base of mountains, it lives in areas where grass and shrubs are common.[15] Its natural habitat in the wild used to mostly be wetlands, but loss of habitat has limited it to ponds and drainage ditches.[11] Its range is extremely restricted; as of 2015, the only places it lives in the wild are Xuancheng, Nanling, Jingxian, Wuhu, Longxi, and Guangde, six small regions in the province of Anhui.[15] It is the sole species in the family Alligatoridae that lives on a continent other than North or South America.[6]

Population and range trend

The oldest discovered record of the Chinese alligator is a skeleton fragment found in western Japan. The fossil is estimated to be from 3 million years ago, in the late Pliocene period. The skeleton showed that the species was larger at the time than it is currently, with a total length of at least 200 centimetres (79 in). According to the Journal of Asian Earth Sciences, alligators are believed to have moved into various parts of Japan either before 25 mya or after 10 mya and became extinct there during the Plio-Pleistocene period, due to tectonic changes and the country's poor climate.[1] In prehistoric times following its extirpation in Japan, the Chinese alligator ranged through much of China. However, in roughly 5000 BC, human civilization started to grow in the country, causing the population of the species to begin to decline.[20]

In the 1700s, much of the Chinese alligator's habitat was replaced with fields to farm on after a large number of people had moved into the area.[21] By the 20th century, its range was reduced to a few small areas around the Yangtze River.[20] In the 1950s, the alligator was found in three distinct areas: the southern area of the Yangtze River (Chang Jiang) from Pengze to the western shore of Lake Tai (Tai Hu), the mountainous regions of southern Anhui, and the provinces of Jiangsu and Zhejiang, primarily in lakes, streams, and marshes. By the 1970s, it was restricted to small parts of the southern Anhui and Zhejiang provinces,[22] during which time the population was about 1,000.[2] In 1998, the largest area the alligator lived in was a small pond along the Yangtze River surrounded by farmland, which held 11 alligators, when the total population was the lowest it had been.[23] In 1999, the Wildlife Conservation Society estimated that 130–150 individuals were left in the wild.[12] From 1998, the population had stabilized and in 2003 began to gradually increase. The Anhui National Nature Reserve for Chinese Alligator (ANNRCA) surveyed the population in 2005 and concluded that the population was 92–114. The survey also inferred that the species' population was growing in four sites, but staying roughly the same in all other areas where the alligator lived.[2] A journal article published in 2012 estimated the population at the time to be 120–150,[24] and another survey in 2015 indicated roughly 136–173 alligators remained in the wild.[2]

Reasons for population decline

Considered to be one of the most endangered crocodilians in the world, the Chinese alligator's biggest threats in the late 20th century were human killing and habitat loss.[2] A majority of the species' wetland habitats were destroyed to construct rice paddies,[25][26] as well as to construct dams.[27] During the 1970s and 1980s, humans would sometimes kill the alligators, because they believed they were pests, out of fear, or for their meat.[23] Thought to have the ability to cure colds and prevent cancer,[5][27] the organs of the Chinese alligator were sometimes sold for use in traditional Chinese medicine.[26] In several restaurants and food centers in China's more prosperous areas, young alligators were allowed to roam free with their mouths taped shut and were subsequently killed for human consumption.[28] In the late 20th century, people living in the range of the Chinese alligator ate its meat due to believing that it was "dragon meat."[21]

The Yangtze River was flooded in the winter of 1957, which is believed to have caused a number of Chinese alligators to drown.[21] Rats, which the Chinese alligators eat, have been poisoned by farmers, also a cause for the diminishing of the species.[5] The organochlorine compound sodium pentachlorophenate was used to kill snails in agricultural fields starting in 1958 and incidentally poisoned the alligators, as well.[21] Other factors that led to the endangerment of the alligator include natural disasters and geographic separation.[2]

Status and conservation

The Chinese alligator is listed as a Class I endangered species as of 1972, which gives it the highest possible degree of legal protection and makes killing or capturing the species in the wild forbidden.[2] It is also listed as a CITES Appendix I species on China's Protection List.[15] Following six previous assessments as endangered from 1982 – 1994, it is classified as critically endangered on the IUCN Red List as of 1996.[2][20] With the help of the council of China, some of the Chinese alligator's habitat has been restored and protected. In 1982, the Anhui National Nature Reserve for Chinese Alligator (ANNRCA) was created, a reserve spanning across the entire distribution range of the Chinese alligator,[15] now covering an area of 18,565 hectares (45,880 acres).[2]

In captivity

Chinese alligators at Shanghai Zoo

At least 20,000 Chinese alligators[a] living in captivity due to captive breeding programs, the first initiated in the 1970s.[29] Captive-born Chinese alligators have been reintroduced back into their native range, boosting the wild population.[30] These releases have proven successful with individuals adapting well to a life in the wild and breeding.[4]

China

The two largest breeding centers for the Chinese alligator are located in, or near, the areas where Chinese alligators are still found in the wild. With roughly 15,000 Chinese alligators in captivity as of 2016,[2] the Anhui Research Center for Chinese Alligator Reproduction (ARCCAR) is the largest of them. Founded in 1979, the ARCCAR was stocked with over 200 alligators collected from the wild over the first decade after its establishment[31] and received alligator eggs collected by the area's residents or ARCCAR's own staff in the nests of wild alligators, as well.[32] The center is located 5 kilometres (3.1 mi) from the city of Xuancheng (30°54′30″N 118°46′20″E / 30.90833°N 118.77222°E / 30.90833; 118.77222),[14] where it makes use of a series of ponds in a small valley.[33] The alligator breeding was so successful that ARCCAR began to use the alligators for local meat consumption and live animals for the European pet market, with the profits from these activities continuing to fund the breeding centers.[34]

The other major breeding center for the species is the Changxing Nature Reserve and Breeding Center for Chinese Alligators (CNRBRCCA), located in Changxing County, Zhejiang Province, about 92 kilometres (57 mi) east of ARCCAR (30°55′15″N 119°44′00″E / 30.92083°N 119.73333°E / 30.92083; 119.73333). Originally known as Yinjiabian Alligator Conservation Area (尹家边扬子鳄保护区), the breeding center was established in 1982.[34][35] Unlike ARCCAR, where alligator eggs are collected by the center's staff for incubation in controlled condition, CNRBRCCA allows eggs to hatch naturally.[33] According to a 2013 official report,[36] CNRBRCCA housed almost 4,000 alligators, including over 2,000 young (1–3 years old), over 1,500 juveniles (4–12 years old), and 248 adults (13+ years old),[37] and by 2016 5,500 specimens were housed there.[2]

In 2003, the ARCCAR received a donation of $1.2 million from the State Forestry and Grassland Administration of China (SFGA) and $0.74 million from the government of Anhui. This allowed the organization to improve the conditions of the specimens they were holding in captivity by creating two breeding areas to hold the alligators, which are 1.6 ha (4.0 acres) each, as well as heightening the fence they had previously built. The CNRBRCCA was also given money, $0.6 million from the SFGA and $0.8 million from the government of Changxing, enabling it to reinstate wetlands for the alligators and enhance the facilities of the organization.[2] Both the ARCCAR and the CNRBRCCA position themselves as tourist attractions, where paying visitors can view alligators and learn about them.[38]

A number of other breeding facilities that house the Chinese alligator exist in various provinces of China, as well, in addition to private breeding farms and museums.[2]

North America and Europe

The Chinese alligator in the Smithsonian National Zoological Park

Although by far the largest number of captive Chinese alligators are at centers in its native country, the species is also kept and bred at many zoos and aquariums in North America and Europe. Some individuals bred there have been returned to China for reintroduction to the wild.[30]

Among the North American zoos and aquariums keeping this species are the Bronx Zoo,[39] Cincinnati Zoo,[30] Philadelphia Zoo,[40] San Diego Zoo,[5] Santa Barbara Zoo,[41] Smithsonian National Zoological Park,[6] and St. Louis Zoo.[11] In Europe, about 25 zoos and aquariums keep the species, such as the Barcelona Zoo (Spain), Bioparco di Roma (Italy), Crocodile Zoo (Denmark), Moscow Zoo (Russia), Pairi Daiza (Belgium), Paradise Wildlife Park (England), Parken Zoo (Sweden), Prague Zoo (Czech Republic), Tallinn Zoo (Estonia), Tierpark Berlin (Germany), and Wildlands Adventure Zoo Emmen (Netherlands).[42]

See also

Notes

  1. ^ Over 15,000 in the Anhui Research Center for Chinese Alligator Reproduction (ARCCAR) and 5,500 in the Changxing Nature Reserve and Breeding Center for Chinese Alligators (CNRBRCCA), as well as those living in other smaller facilities

References

  1. ^ a b Iijima, Masaya; Takahashi, Keiichi; Kobayashi, Yoshitsugu (2016). "The oldest record of Alligator sinensis from the Late Pliocene of Western Japan, and its biogeographic implication". Journal of Asian Earth Sciences. 124: 94–101. Bibcode:2016JAESc.124...94I. doi:10.1016/j.jseaes.2016.04.017.
  2. ^ a b c d e f g h i j k l m n o p q r Crocodile Specialist Group (1996). "Alligator sinensis". IUCN Red List of Threatened Species. 1996: e.T867A13086708. doi:10.2305/IUCN.UK.1996.RLTS.T867A13086708.en.
  3. ^ Wu, Ziaobang; Zhou, Kaiya; Wang, Yiquan; Zhu, Weiquan (October 2003). "Complete mitochondrial DNA sequence of Chinese alligator, Alligator sinensis, and phylogeny of crocodiles". Chinese Science Bulletin: 2050–2054. doi:10.1360/03wc0076. Retrieved December 20, 2018.
  4. ^ a b "The largest group of Chinese alligators released to the wild". UNDP in China. June 8, 2016. Retrieved April 23, 2017.
  5. ^ a b c d e f g h Perry, Tony (July 4, 2012). "San Diego Zoo gets two Chinese alligators in preservation effort". Los Angeles Times. Ross Levinsohn. Retrieved December 9, 2018.
  6. ^ a b c d e f g h i j k l "Chinese alligator". Smithsonian's National Zoo. April 25, 2016. Retrieved December 9, 2018.
  7. ^ a b Wood 1976, p. 115.
  8. ^ a b c d e Reading & Miller 2000, p. 72.
  9. ^ a b "American alligator". Smithsonian's National Zoo. April 25, 2016. Retrieved December 12, 2018.
  10. ^ a b c d Grigg 2015, p. 6.
  11. ^ a b c d e f "Chinese Alligator". Saint Louis Zoo. Retrieved December 10, 2018.
  12. ^ a b c d "Alligator sinensis". Arkive.org.
  13. ^ a b Neill 1971.
  14. ^ a b c d e Reading & Miller 2000, p. 73.
  15. ^ a b c d e f Zhang, Fang; Messenger, Kevin; Wang, Yong (2015). "Relationship between nest defence behaviours and reproductive benefits in Chinese alligators". Amphibia-Reptilia. 36 (2): 141–147. doi:10.1163/15685381-00002990.
  16. ^ a b c d e Thorbjarnarson & Wang 2010, pp. 122–123.
  17. ^ Thorbjarnarson & Wang 2010, p. 97.
  18. ^ Grzimek 2003, pp. 173–176.
  19. ^ Wang, Xianyan; et al. (2009). "Why do Chinese alligators (Alligator sinensis) form bellowing choruses: A playback approach". The Journal of the Acoustical Society of America. 126 (4): 2082–7. Bibcode:2009ASAJ..126.2082W. doi:10.1121/1.3203667. PMID 19813817. {{cite journal}}: Explicit use of et al. in: |last2= (help)
  20. ^ a b c Thorbjarnar, John. "Chinese Alligator". Wildlife Conservation Society. Retrieved December 11, 2018.
  21. ^ a b c d Reading & Miller 2000, p. 75.
  22. ^ Thorbjarnarson, John; et al. (2002). "Wild populations of the Chinese alligator approach extinction". Biological Conservation. 103 (1): 93–102. doi:10.1016/s0006-3207(01)00128-8. {{cite journal}}: Explicit use of et al. in: |last2= (help)
  23. ^ a b Gallagher, Sean. "The Chinese Alligator, A Species On The Brink". National Geographic Society Newsroom.
  24. ^ Chuanpeng, Nie; Yanyan, Li; Zhao, Juan; Wu, Xiaobing (2012). "Extremely high major histocompatibility complex class IIb gene intron 2 variation and population structure in Chinese alligator". Journal of Genetics. 93: 86–91. doi:10.1007/s12041-012-0174-2.
  25. ^ Yoon, Carol Kaesuk (August 21, 2012). "Rare Alligator Is Threatened As China Feeds Its People". The New York Times. A.G. Sulzberger. Retrieved December 9, 2018.
  26. ^ a b "Chinese Alligator (Alligator sinensis)". Crocodilians: Natural History & Conservation. Retrieved January 2, 2012.
  27. ^ a b "Ten Threatened and Endangered Species Used in Traditional Medicine". Smithsonian. Smithsonian Institute. October 18, 2011. {{cite web}}: Italic or bold markup not allowed in: |work= (help)
  28. ^ Chang, L. T.; Olson, R. (May 2008). "Gilded Age, Gilded Cage". National Geographic.
  29. ^ Thorbjarnarson & Wang 2010, p. 10.
  30. ^ a b c "Chinese Alligator". Cincinnati Zoo and Botanical Garden. Retrieved January 29, 2012.
  31. ^ Thorbjarnarson & Wang 2010, pp. 175–176.
  32. ^ Thorbjarnarson & Wang 2010, pp. 200–202.
  33. ^ a b Thorbjarnarson & Wang 2010, p. 195.
  34. ^ a b Thorbjarnarson & Wang 2010, p. 205.
  35. ^ "尹家边扬子鳄保护区" [Yinjiabian Chinese Alligator Reserve]. Huzhou Municipal People's Government (in Chinese). November 26, 2008. Archived from the original on June 14, 2017. Retrieved December 14, 2018.
  36. ^ "从抢救保护到放归发展　浙江长兴成功繁殖扬子鳄" [From rescue and protection to reintroduction development. Changxing in Zhejiang successfully propagated Chinese Alligators]. China Government Network Central (in Chinese). April 29, 2013.
  37. ^ Liu, Victor H. (2013). "Chinese Alligators: Observations at Changxing Nature Reserve & Breeding Center" (PDF). IRCF Reptiles and Amphibians. 20 (4): 172–183.
  38. ^ Thorbjarnarson & Wang 2010, pp. 195, 198, 205.
  39. ^ "World's Most Endangered Alligator Making a Comeback – in Shanghai". WCS Newsroom. October 26, 2016. Retrieved December 10, 2018.
  40. ^ "Chinese alligator". Philadelphia Zoo. Retrieved December 10, 2018.
  41. ^ "List of Animals". Santa Barbara Zoo. Retrieved April 13, 2018.
  42. ^ "Chinese alligator". Zootierliste.

Sources

Further reading

Wikimedia Commons has media related to Alligator sinensis.
Wikispecies has information related to Alligator sinensis.
  • Hu, Y.; Wu, X. B. (2010). "Multiple paternity in Chinese alligator (Alligator sinensis) clutches during a reproductive season at Xuanzhou Nature Reserve". Amphibia-Reptilia. 31 (3): 419–424. doi:10.1163/156853810791769446.
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