Alligator sinensis

Geographic Range

Currently, Chinese alligators reside naturally within the lower Yangtze River basin, located along the central Pacific coast of China. Historically, when populations were more numerous, they spread over much greater areas. Literature cites this species as early as the third century A.D., including reference that it lived in other areas of China and possibly even Korea. It was estimated in 1998 that the geographic range of Chinese alligators had decreased by over ninety percent in the past twenty years.

• Biogeographic Regions
• oriental oriental
  • native native

Habitat

Chinese alligators live in a subtropical, temperate region. They live in wetlands and swamps, ponds, lakes, as well as freshwater rivers and streams.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• temporary pools

• Wetlands
• marsh marsh

• Other Habitat Features
• riparian riparian

Physical Description

Chinese alligators are yellowish gray in color with pronounced black spotting of the lower jaw. They have four short claw-tipped limbs with five partially webbed toes on each limb. Their long, thick tail provides a primary locomotive force in the water. They have osteoderms, dermal bone lying over the epidermis used as armor, covering both the back and underside of the body. Unlike crocodiles, their fourth mandibular teeth in the lower jaw lie in sockets in the upper jaw, and are unexposed when the jaws are closed. Also characteristic of this species is the upturned snout. Similar to caimans , but unlike their closest relatives, American alligators ( Alligator mississippiensis ), Chinese alligators have a bony plate in the upper eyelid.

Juveniles appear very similar to adults with the exception that juveniles have distinctive yellow bands along their bodies. They have an average of five bands on their bodies, and eight on their tails. As adults mature, their coloring becomes less and less conspicuous.

Males have been recorded up to 2.2 m long from snout to tail, although the average size is 1.5 m. Females have been recorded up to 1.7 m, averaging around 1.4 m.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Development

Young alligators begin development as hard-shelled eggs laid in a nest. Sex is determined by the temperature of the egg during incubation. Females are produced at lower incubation temperatures of below 28°C, while males are produced at higher temperatures of above 33°C. For this reason nests can produce a majority of one sex over the other based on the temperature of the nest. Similarly, nests can produce different sexes based upon what layer, how deep, or how shallow the egg was buried. The critical temperature for Chinese alligators, producing an even number of males and females is 31°C. The incubation period is approximately seventy days. Hatchlings weigh about 30 g and average slightly over 21 cm long.

Rapid growth occurs for the first five years of life. Reproductive maturity in Chinese alligators is reached after five to seven years. In captivity they are known to reproduce into their fifties.

• Development - Life Cycle
• temperature sex determination

Reproduction

The mating season occurs annually in June, a month after the rainy season has begun. Both males and females will vocalize with a bellow or roar to communicate their location and find a mate. Another feature used in mating shared by both males and females is a musk gland under the lower jaw that produces an attractive scent. Male alligators are polygynous, a male may fertilize several females in one mating season. Females are known to have only one mate each season.

• Mating System
• polygynous polygynous

In July females make a mound nest out of surrounding vegetation and mud on land surrounding lakes or rivers. Females will use coordinated movements of the front and hind limbs to form a pile in the center just under 1 m high. Nests are often located near a burrow so that the mother can attend to her nest during incubation. She will lay an average of ten to forty eggs in a depression on top of the mound, and then cover them with more vegetation. Chinese alligators reach sexual maturity in 5 to 7 years.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

Females guard the nest from surrounding predators, visiting it frequently, whereas males have no parental involvement. Hatchlings will emerge in September. Responding to their vocalizations, females will remove any debris covering the nest, and bring their offspring to the water. They may even help the hatchlings break out of their egg shells by slowly rolling them around in the mouth and lightly cracking the shell by pressing the egg between the roof of the mouth and tongue. Females are known to live with their young through the first winter, but little else is known about the specific interactions between adult Chinese alligators and their young.

• Parental Investment
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • protecting
    • female

Lifespan/Longevity

Both male and female Chinese alligators, once thought to live only into their 50's, have now reached into their 70's in captivity.

Behavior

Chinese alligators are dormant from late fall into early spring, when temperatures are cool. They create burrows on the banks of wetlands that are approximately 1 m deep, 0.3 m in diameter and 1.5 m long. Burrows are used throughout the year, but primarily in the winter. These burrows can also be very elaborate, and may house more than one alligator. Once they emerge from their burrows in April, they spend time basking in the sun to raise their body temperature, as they are ectotherms and cannot create their own heat. Once their body temperature has normalized, they return to their normal nocturnal ways. They are aquatic animals, and can also use the water to thermoregulate by staying in the upper water columns heated by the sun, or moving to shaded waters to cool off. Mating rituals occur in the spring. Chinese alligators are thought to be the most docile of the crocodilians .

• Key Behaviors
• natatorial natatorial
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• hibernation hibernation
• solitary solitary
• territorial territorial
• dominance hierarchies dominance hierarchies

Communication and Perception

Chinese alligators use a bellowing sound, vocalized by both males and females, as a way to communicate location. Although this is used much more frequently during the mating season, it is also used at other times throughout the year. Both males and females use body language to communicate. One example of this is slapping the water with their lower jaws. Another is snapping their jaws as a warning signal. During mating, the male may create subaudible vibrations in the water to attract a mate. Also in mating, the female may rub up against the male to indicate she is ready to mate.

• Communication Channels
• tactile tactile
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• scent marks scent marks
• vibrations vibrations

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• vibrations vibrations
• chemical chemical

Food Habits

Chinese alligators are nocturnal, carnivorous predators. Adults prey mostly on fish, snails, clams, as well as small mammals and waterfowl. There is some speculation that they may prey on turtles as well. Younger alligators will eat insects and other small invertebrates

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
  • piscivore piscivore
  • insectivore insectivore
  • eats non-insect arthropods
  • molluscivore molluscivore

• Animal Foods
• birds
• mammals
• reptiles
• fish
• insects
• mollusks

Predation

Adult Chinese alligators have only one predator, humans. Although protected by law, they are still in danger of hunting by humans. Alligators are hunted for their meat and internal organs for alternative medicine use and also food. They are not hunted for skin because the skin on their bellies, customarily used as a textile in other crocodilian species, is covered in osteoderms and therefore inadequate.

Juvenile alligators and eggs are most at risk due to their size. Despite the protection of the mother alligator, the young ones are at a high risk of predation by other larger animals. These predators could be anything from other adult alligators to large birds and fish.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Due to their scarcity, Chinese alligators currently have little to no impact on the ecosystems in which they live. Historically they were important aquatic predators.

Economic Importance for Humans: Positive

Historically, humans used parts of Chinese alligators for alternative medicine, especially to treat afflictions of the gall bladder. They were also used as a food source. Because there are so few in the world today, they have little to no impact on humans.

• Positive Impacts
• food food
• ecotourism ecotourism
• source of medicine or drug source of medicine or drug

Economic Importance for Humans: Negative

Because of their docile nature, and limited abundance in the world, the possibility of attacks by Chinese alligators is highly unlikely. There have never been any attacks recorded by Chinese alligators. Despite this information, if provoked, it is possible that an alligator would attack, and should be considered potentially dangerous.

• Negative Impacts
• injures humans
  • bites or stings
• crop pest

Conservation Status

Chinese alligators are a critically endangered species. They are currently on the IUCN Red List of threatened species, and have been since 1986. Previously, they were listed in the IUCN Amphibia-Reptilia Red Data Book. Habitat destruction is identified as the primary cause for their decline. Other factors include pollution and human intolerance and predation. Although they are fairly successful in captivity worldwide, there are thought to be less than 150 individuals alive in the wild today. Laws have been set in place to protect these animals, and luckily the small region in which they live is somewhat isolated. The Yangtze River basin floods every year, preventing its use as farm land and from permanent human residency. Although there has been much success in breeding Chinese alligators in captivity, little effort is being made to release captive bred individuals to replenish the wild population.

Other Comments

Other common names: English: Chinese alligator, Yangtze alligator; Chinese: Tou lung, Yow lung, T’o; French: alligator de Chine; German: China-alligator; Spanish: alligator de China.

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Lauren Groppi (author), Kalamazoo College, Ann Fraser (editor, instructor), Kalamazoo College.

References

Alderton, D. 1991. Crocodiles and Alligators of the World . New York: Facts on File.

Behler, J., D. Behler. 1998. Alligators and Crocodiles . Stillwater: Voyager Press.

Mertz, L. 2003. Alligators and caimans. Pp. 171-176 in Grizmek's Animal Life Encyclopedia , Vol. 7, 2 Edition. Farmington Hills, Michigan, USA: Gale Group.

Neill, W. 1971. The Last of the Ruling Reptiles: Alligators, Crocodiles, and Their Kin . New York: Columbia University Press.

Pope, C. 1955. The Reptile World: A Natural History of Snakes, Lizzards, Turtles, and Crocodilians . New York: Alfred A Knopf.

Therbjarnarson, J., X. Wang, L. He. 2001. Reproductive ecology of the Chinese alligator (Alligator sinensis) and implications for conservation. Journal of Herpetology , 35: 553-558.

1980. Alligator. The New International Wildlife Encyclopedia , Vol. 1. Milwaukee: Purnell Reference Books.

1994. Chinese Alligator. Pp. 782-783 in Encyclopedia of Endangered Species . Detroit: Gale Research.

2002. Crocodiles. Pp. 295-299 in Magill's Encyclopedia of Science: Animal Life , Vol. 1. Pasadena: Salem Press.

2002. Crocodilians. Pp. 212-221 in Firefly Encyclopedia of Reptiles and Amphibians . Buffalo: Firefly Books.