Chinese giant salamander

The Chinese giant salamander (Andrias davidianus) is the largest salamander and largest amphibian in the world, reaching a length of 1.8 m (5.9 ft), although it rarely reaches that size today. It is fully aquatic and is endemic to rocky mountain streams and lakes in China. It has been introduced to Kyoto Prefecture in Japan and Taiwan. It is considered critically endangered in the wild due to habitat loss, pollution, and overcollection, as it is considered a delicacy and used in traditional Chinese medicine. On farms in central China, it is extensively farmed and sometimes bred, although many of the salamanders on the farms are caught in the wild. It has been listed as one of the top-10 'focal species' in 2008 by the Evolutionarily Distinct and Globally Endangered project. The Chinese giant salamander is considered to be a 'living fossil'. Although protected under Chinese law and CITES Appendix I, the wild population has declined by more than an estimated 80% since the 1950s. Although traditionally recognized as one of two living species of Andrias salamander in Asia, the other being the Japanese giant salamander, evidence indicates that the Chinese giant salamander may be composed of at least five cryptic species, further compounding each individual species' endangerment. The correct scientific name of this species has been argued to be Andrias scheuchzeri (in which case Andrias davidianus would be a junior synonym) – a name otherwise restricted to an extinct species described from Swiss fossils. It has also been given the moniker of 'living fossil' for being part of the family Cryptobranchidae which dates back 170 million years. It is one of only three extant species of the family, the others being the slightly smaller, but otherwise very similar Japanese giant salamander (Andrias japonicus), and the far smaller North American hellbender (Cryptobranchus alleganiensis). A 2018 study of mitochondrial DNA revealed that there are five wild clades of the Chinese giant salamander, as well as two only known from captives (their possible wild range is unknown). They diverged from each other 4.71–10.25 million years ago and should possibly be recognized as cryptic species. Despite this deep divergence, they can hybridize among each other, and also with the Japanese giant salamander. It has a large head, small eyes, and dark, wrinkly skin. Its flat, broad head has a wide mouth, round, lidless eyes, and a line of paired tubercles that run around its head and throat. Its color is typically dark brown with a mottled or speckled pattern, but it can also be other brownish tones, dark reddish, or black. Albinos, which are white or orange, have been recorded. All species of giant salamanders produce a sticky, white skin secretion that repels predators. The average adult salamander weighs 25–30 kg (55–66 lb) and is 115 cm (3.77 ft) in length. It can reach up to 50 kg (110 lb) in weight and 180 cm (5.9 ft) in length, making it the largest amphibian species. The longest recently documented Chinese giant salamander, kept at a farm in Zhangjiajie, was 180 cm (5.9 ft) in 2007. At 59 kg (130 lb), both this individual, and a 140 cm (4 ft 7 in) long, 52 kg (114 lb) individual found in a remote cave in Chongqing in December 2015, surpassed the species' typically reported maximum weight. The giant salamander is known to vocalize, making barking, whining, hissing, or crying sounds. Some of these vocalizations bear a striking resemblance to the crying of a young human child, and as such, it is known in the Chinese language as the 'infant fish' (娃娃鱼 / 鲵). The Chinese giant salamander has been recorded feeding on insects, millipedes, horsehair worms, amphibians (both frogs and salamanders), freshwater crabs, shrimp, fish (such as Saurogobio and Cobitis) and Asiatic water shrew. Presumably ingested by mistake, plant material and gravel have also been found in their stomachs. Cannibalism is frequent; in a study of 79 specimens from the Qinling–Dabashan range, the stomach content of five included remains of other Chinese giant salamanders and this made up 28% of the combined weight of all food items in the study. The most frequent items in the same study were freshwater crabs (found in 19 specimens), which made up 23% of the combined weight of all food items. It has very poor eyesight, so it depends on special sensory nodes that run in a line on the body from head to tail. It is capable of sensing the slightest vibrations around it with the help of these nodes. Based on a captive study, most activity is from the earlier evening to the early night. Most individuals stop feeding at water temperatures above 20 °C (68 °F) and feeding ceases almost entirely at 28 °C (82 °F). Temperatures of 35 °C (95 °F) are lethal to Chinese giant salamanders.