Hainan Knobby Newt
© 2015 Axel Hernandez (1 of 3)
Author: Axel Hernandez
Tylototriton hainanensis FEI, YE, YANG 1984
Diagnosis and taxonomyT. hainanensis was described after an adult male (CIB 641111379) collected with three paratypes at Nalong, Wuzhishan, Hainan at 770 meters above sea level in 1964. A paratypic adult female (CIB 820619) and six subadults were collected in Diaoluoshan, Lingshui County, in April, May and November of 1982. This species is well distinct from the other forms of Yaotriton. Following the original description by FEI et al. (1984), males measure up to 14.8 cm TL, and females are smaller with a maximum total length of 12.5 cm, but more robust. This species is characterized by a head that is flat and wider than long, well-developed bony ridges, a rounded snout, and a slender and flattened body with a distinct and segmented vertebral ridge. It has 14 - 16 prominent dorsolateral glandular warts, a rough skin with fine granules, small transverse wrinkles on the venter, and a laterally compressed tail ending in a rounded tip. Its tail is shorter than the snout-vent length. Its dorsal color is dark brown and the ventral side greenish gray. The tips of the digits, surroundings of cloaca, and lower margin of the tail are orange. Some individuals have orange dorsolateral warts (FEI et al. 1984, FEI et al. 2006, 2014). All this renders Tylototriton hainanensis similar to T. asperrimus, and it was regarded as a population of the latter species when it was first discovered (LIU et al. 1973) until a study of its mitochondrial DNA revealed it to be distinct and a sister taxon to the recently described species T. notialis and T. ziegleri (STUART et al. 2010, NISHIKAWA et al. 2013b).
On Hainan, the populations in the west of the island differ chromatically from those in the center. Specimens from the Diaoluoshan Nature Reserve have a lighter coloration with light brown markings and nodules, and the tip of the tail will be orange during the rainy season.
DistributionThe species is endemic to the Chinese island of Hainan. It is known from only five areas: Bawangling National Nature Reserve, Diao Luo Shan Forest Park, Jianfengling Nature Reserve, Yinggeling Provincial Nature Reserve, and Mt. Whuzi (“Five Finger Mountain”).
Habitat, ethology and ecologyThis is a scarce species with secretive habits that is difficult to locate in the rainy season. It is generally found at elevations between 770 and 950 m a.s.l. (IUCN 2010) and occurs in subtropical or tropical moist lowland forests with freshwater marshes. In the Yinggeling Nature Reserve, the species is found at distinctly higher elevations of 1,200 to 1,750 m a.s.l. on the crest of the mountain and at Nanmaola. In the Jianfengling Nature Reserve, it inhabits tropical hill forest where the dominant vegetation consists of Fagaceae spp., Nephelium topengii, Altingia chinensis, Endospermum chinense, Livistona saribus, and Cyatheaceae spp. In the Diaoluoshan Nature Reserve, the annual average temperature is 20.0 °C with a maximum of 24.0 and a mean minimum of 16.0 °C. The period from November through January is the dry season, followed by a wet season from April through October that will produce most of the 2500 mm in annual precipitation. T. hainanensis is predominantly terrestrial, moves about slowly, and leads a very secretive life throughout the year. It migrates to temporary pools choked with decaying leaf litter in April/May to spend a short period in water with a pH of 4.1 to 6.5 and a low oxygen content (0.7 to 1.1 ppm). Larvae were observed in the company of tadpoles of Occidozyga lima during a survey in Diaoluoshan by the author in 2012. These small to medium-sized, shallow pools of 10 cm deep on average (maximum 20 cm) were warm (19 - 21.0 °C), often difficult to access, and shaded by a dense vegetation canopy. Air temperatures were between 22.0 and 24.0 °C and the relative humidity was nearly saturated (80 to 90%). The main predators are aquatic snakes.
ReproductionClutches were found in mid-May, which suggests that the breeding season of this species probably begins in April/May. The eggs are deposited under rocks or dead leaves under dense vegetation on land near streams, as in T. vietnamensis. A clutch may contain 58 to 90 eggs (FEI et al. 1984).
Status, threats and conservationThis species inhabits only a small area (Diaoluoshan: 30.5 km², Wuzishan: 820 km²). In the Jianfengling National Nature Reserve, its population density is estimated at around 30 individuals per square kilometer (WANG et al. 2008), and this is probably the largest population in existence, facilitated by an environment with a high canopy density and without major anthropogenic disturbances (only eco-tourism). T. hainanensis is one of the rarest and most endangered species of the subgenus Yaotriton, suffering greatly from deforestation and the effects of climate change. It is considered “Endangered” by the IUCN and Class-II protected in China.
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Citation: AmphibiaWeb. 2019. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 26 May 2019.
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