The Chinese crocodile lizard (Shinisaurus crocodilurus) is a semiaquatic species of lizard found only in cool forests in southeast China and northeast Vietnam. This is a rare and little-studied lizard, which is listed in CITES Appendix I, which regulates international trade of specimens. It is the only living member of the Shinisauria, a group of lizards whose fossil record extends back to the Early Cretaceous, over 120 million years ago.
Chinese crocodile lizards are characterized by their green, colored with reddish necks. They often have alternating bands of light and dark patterns. Perhaps their most distinctive features are the rows of bony scales down the back and muscular tail, imitating those of a crocodile. Additionally, Chinese crocodile lizards are sexually dimorphic and can be distinguished visually. Adult males are larger and more colorful than females, with their color intensifying during the breeding season.
Chinese crocodile lizards are found in Guangxi and Guandong provinces of southeastern China. The Vietnamese subspecies is only found on Yên Tử Mountain in Quảng Ninh and Bac Giang provinces of northeastern Vietnam. These lizards live alongside clear streams within subtropical broadleaf evergreen forests. They prefer remote streams in undisturbed areas such as mountain ridges and dense forests. Chinese crocodile lizards live in a relatively cool, monsoonal climate at moderately high elevations. They usually use tree holes, rocks, and vegetated perches as shelter.
Chinese crocodile lizards are usually active in the morning and afternoon. They spend much of their time in shallow water or in overhanging branches and vegetation, where they hunt their prey. They are "sit-and-wait" predators, perching on branches near streams and waiting patiently until prey items are sighted. Chinese crocodile lizards are territorial and in a given pond or stream, one sole lizard will occupy the entire space. They will widen their mouths to establish dominance, which is known as gaping. Similar to other lizards, Chinese crocodile lizards would also swing their tails and lunge at their competitors. The dominant lizard will lunge and whip its tail, without force, at the subordinate lizard. The result of this is often little to no physical harm done to the subordinate. However, the subordinate lizard will retreat from the dominant's territory. Another interesting dominance-establishing behavior for Chinese crocodile lizards is push-up behavior. The lizard would straighten its forelimbs and level its head. Unlike other lizards, they only perform this push-up motion with their anterior portion. While doing push-ups, they will also sometimes bob their head in a circular motion. Chinese crocodile lizards are usually seen singly but they may congregate together before hibernation or often hibernate communally.
Chinese crocodile lizards are carnivores and feed on various vertebrates and invertebrates. They eat terrestrial worms, spiders, katydids, and aquatic shrimp. Vertebrate prey includes tadpoles, small fish, and occasionally frogs and lizards. The Vietnamese subspecies prefers terrestrial invertebrates, such as cockroaches, crickets, and particularly earthworms.
Chinese crocodile lizards breed between July and August. Courtship often begins at the end of winter; before mating the adult male appearance changes to a more vibrant coloration. Adult males display with head-nodding and approaching the females. Females are viviparous and give birth to 2-12 fully developed young every spring. The gestation period lasts for up to 9 months. This means that the mother does not have to take care of their offspring and that they can survive independently. On average, young Chinese crocodile lizards become fully mature and are able to reproduce by the age of 3 years.
The main threat to Chinese crocodile lizards is habitat loss, mainly due to logging. Removal of broadleaf evergreen foliage makes streams more volatile, leading to flooding and drying cycles which are unsuitable for the lizards. Other sources of habitat loss include mining pollution, small-scale farming, and dam construction leading to water flow changes. Environmentally destructive fishing styles, such as electrofishing and poisoning, contribute to stream degradation. Another prominent threat is poaching for the pet trade, meat, and traditional Chinese medicine as a claimed cure for insomnia. In Vietnam, the local subspecies suffers from similar threats, as well as road construction and coal mining. Local tourism has also led to habitat loss and stream pollution. Habitat loss will be amplified by climate change: one model argues that forest habitats with a climate suitable for the Chinese subspecies will be eliminated by 2080.
According to the IUCN Red List, the total Chinese crocodile lizards population size in China is estimated to be 950 individuals. As of 2015 the total population size of this species in Vietnam was estimated to be 41 mature individuals. Currently, the Chinese crocodile lizard is classified as Endangered (EN) on the IUCN Red List, and its numbers today are decreasing.
