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Alligator sinensisChinese alligator, T'o, Yow Lung, Yangtze alligator

By Lauren Groppi

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. (Mertz, 2003; Behler and Behler, 1998; Neill, 1971)

Habitat

Chinese alligators live in a subtropical, temperate region. They live in wetlands and swamps, ponds, lakes, as well as freshwater rivers and streams. (Mertz, 2003)

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

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. (Mertz, 2003; "Chinese Alligator", 1994)

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. (Neill, 1971)

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. (Mertz, 2003)

  • Sexual Dimorphism
  • male larger
  • Range length
    1.4 to 2.2 m
    4.59 to 7.22 ft
  • Average length
    1.4 - 1.5 m
    ft

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. ("Crocodiles", 2002; Alderton, 1991; Therbjarnarson, et al., 2001)

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. (Mertz, 2003; Alderton, 1991)

  • 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. ("Alligator", 1980; "Crocodiles", 2002; Alderton, 1991)

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. ("Alligator", 1980; "Crocodilians", 2002; Alderton, 1991; "Alligator", 1980; "Crocodilians", 2002; Alderton, 1991)

  • Breeding interval
    Chinese alligators breed once a year.
  • Breeding season
    Mating occurs in June, followed by egg-laying in mid-July. The female guards the nest for the 70 day incubation period until the hatchlings emerge in September.
  • Range number of offspring
    10 to 40
  • Range age at sexual or reproductive maturity (female)
    5 to 7 years
  • Range age at sexual or reproductive maturity (male)
    5 to 7 years

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. (Mertz, 2003; "Crocodiles", 2002; "Crocodilians", 2002)

  • 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. (Mertz, 2003)

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. (Mertz, 2003; Alderton, 1991; Neill, 1971)

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. (Mertz, 2003; "Crocodiles", 2002; Alderton, 1991)

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 (Mertz, 2003; Mertz, 2003)

  • 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. (Alderton, 1991)

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. ("Alligator", 1980)

  • Anti-predator Adaptations
  • 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. (Mertz, 2003)

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. (Alderton, 1991)

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. (Alderton, 1991; Alderton, 1991)

  • 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. (Mertz, 2003; Behler and Behler, 1998; Pope, 1955)

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. (Mertz, 2003)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

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

Glossary

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

piscivore

an animal that mainly eats fish

polygynous

having more than one female as a mate at one time

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

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

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

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

2002. Crocodilians. Pp. 212-221 in T Halliday, K Adler, eds. Firefly Encyclopedia of Reptiles and Amphibians. Buffalo: Firefly Books.

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 M Hutchins, J Murphy, N Schlager, eds. 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.

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