【明報專訊】The longest river in China — the Yangtze (or Chang Jiang 長江) is not only the cradle of ancient Chinese civilisation, but also the home of rare and precious wildlife such as Chinese alligators (揚子鱷). Chinese alligators are historically associated with the mythical Chinese dragon. Some local people still call them 'Tu Long' (土龍), which means 'earth dragon'.

Alligator, alligator, where are you?

Chinese alligators prefer slow-moving freshwater rivers and streams, including lakes, ponds and swamps (沼澤). Once widely distributed throughout the eastern Yangtze River system, they are now mostly restricted in the Anhui (安徽) and Zhejiang (浙江) provinces in the lower Yangtze. They build extensive burrows (地洞) with numerous air holes. Like other reptiles, alligators are exothermic animals (變溫動物) which means their body temperature changes with the surrounding temperature. They adjust their body temperature by moving in and out of sunlight or their burrows.

Temperatures determine the sex

Chinese alligators reach sexual maturity between 5 and 6 years of age. Temperatures during the first few weeks of incubation (孵化) determine the sex of the alligators. Females will be hatched at lower incubation temperatures, while males at higher temperatures. At birth, the young appear very similar to adults with the exception that they have distinctive yellow bands along their bodies, which fade off as they grow up.

Hiding away from winters

Chinese alligators are opportunistic feeders, which means they have a variable diet to adapt to the environment. During the warm months from April to October, they hunt mainly at night when their prey is asleep. During winter, Chinese alligators stay underground in caves or burrows and brumate. Brumation (低代謝狀態) means the animal's activity, body temperature, heart rate and respiratory rate drops as if the animal were in hibernation, but it moves on warmer winter days and find water. This behaviour can be found in other exothermic animals, and is a skill to survive in the cold.

Too soon to be gone

Due to intense population pressure, alligators' wetland habitats are being converted into paddy fields (稻田) and duck farms. Only found now at the edge of the rice paddies, fewer than 150 Chinese alligators are left in the wild and they are now catergorised as "critically endangered'. If the situation continues to deteriorate, they will disappear from the wild in less than one or two decades. Let's protect wetlands and rivers to save this endangered species!

Text & photos: Ocean Park Hong Kong

■Glossary

distinctive (adj) 特別的

hibernation (n) 冬眠

convert (v) 轉變

deteriorate (v) 惡化

[Smarties' Power English 第220期]