Distribution is very local and populations are small, making this as well as the other Taiwanese Hynobius species vulnerable to habitat destruction and degradation, due to development of infrastructure for tourism. Hynobius arisanensis was initially protected within Yushan National Park and Tawushan Nature Preserve, and listed as endangered (Stuart et al., 2008) or vulnerable (IUCN, 2010). Currently all five salamander species in Taiwan are protected by the Wildlife Conservation Law. Studies are undertaken to monitor the effect of concrete constructions on habitat and mobility of salamanders (Hou et al., 2010).
The interior line of vomerine teeth is very long, exceeding the posterior margin of eye. 11 to 13 costal grooves (Lai & Lue, 2008). The fifth toe often poorly developed into a protuberance. Tail tip pointed. Dorsal color is dark brown with numerous small yellowish spots (Fei et al., 2006).
2n=58, 1M, 2M, 3M, 4ST, 5M, 6M, 7SM, 8SM, 9M, 10SM, 11SM, 12ST, 13M, 14ST, 15ST, 16ST, 17ST, 18ST, 19ST, m (20–39), from Seto and Utsunomiya 1987.
M: metacentric; SM: submetacentric; T: telocentric; ST: subtelocentric; m: micro-chromosome
The mitochondrial sequence is available in Lai & Lue (2008).
Hynobius arisanensis is similar to H. sonani genetically and morphologically. Karyology also shows the resemblance between these two species (Iizuka & Kakegawa, 1989). But they are different in coloration. Hynobius arisanensis is brown with small white spots, but H. sonani is brown with large irregular white blotches (Lai & Lue, 2008).
A relatively small salamander with total length around 10 to12 cm. Head is flat. Snout is rounded. Gular fold prominent. Behind the eye, a horizontal groove crosses over the gular fold. The interior line of vomerine teeth is very long (around 29 teeth), exceeding the posterior margin of eye. The exterior line is very short with only 4 teeth. Tail length is shorter than snout-vent length. Tip of tail is pointed (Fei et al., 2006). The fifth digit is rudimentary as a small protuberance. No tubercles on palms or soles. 11 to 13 costal grooves. When limbs are adpressed, fingers and toes overlap in some specimens but do not meet in others (Lai & Lue, 2008). Dorsal coloration is light to dark brown with white small spots. In some specimens the spots are arranged into transverse rings. Venter is light yellow (Fei et al., 2006).
All measurements are from Lai & Lue (2008).
Male (72 specimens). Snout-vent length: 45.7–69 mm; Tail length: 26.7–55.3 mm; Head length: 8.6–15.2 mm; Head width: 6.3–11.2 mm; forelimb length: 10.9–16.4 mm; hind-limb length: 13.1–18.7 mm.
Female (40 specimens). Snout-vent length: 48–65.7 mm; Tail length: 29.7–58.6 mm; Head length: 8.3–13.3 mm; Head width: 6.7–10.7 mm; forelimb length: 9.6–15.2 mm; hind-limb length: 12.2–18.7 mm.
After descriptions of the first three Taiwanese species (Maki, 1922), Hynobius sonani, H. formosanus and H. arisanensis, Dunn (1923) considered the latter two species as synonyms of H. sonani. Sato (1941) recognized H. sonani and H. formosanus but treated H. arisanensis as a synonym of H. formosanus. The latest data based on morphology and genetics from Lai & Lue (2008) support the validity of H. arisanensis and suggest a sister relationship with H. sonani.
Central to southern parts of Taiwan at altitudes of 2,000 m or higher in Mount Ali, Mount Yu and Mount Dawu.
The species, like the other Taiwanese Hynobius species, occurs in high-elevation montane areas, in woodlands, and broadleaf and coniferous forests, and the transition zone between coniferous forests and alpine bamboo grasslands (Lai & Lue, 2008): Areas with low temperatures, high annual precipitation, little disturbance and high humidity. The animals spend most of their lives under logs and rocks near small cool creeks and seepage areas with moist substrate. Microhabitat studies indicate that H. arisanensis prefers moist soils under logs of decaying wood on slopes with small creeks and seepages (Lai, 2009). Adult salamanders usually search for food actively at night under debris on the forest floor and prey mainly on sow bugs, earth worms, and other terrestrial invertebrates. Their natural enemies are snakes, pheasants and other predators (see refs in Lee et al., 2006 and Hou et al., 2010). The animals congregate near the creeks during the dry season, from November to April, and disperse in the wet season from May to October, most of them not venturing more than 5 m from the water. The home range is small (Chen & Lue, 1986).
Breeding season is between late winter and early spring. Adults mate in the ponds next to streams/creeks. Parental care includes guarding the eggs sac and larvae by both sexes (see refs in Hou et al., 2010). Egg sacs are attached to the bottom of stones in water. Each egg sac contains only 4-8 eggs. Larvae hatch after two months and reportedly feed on algae and decomposed plant residue (refs in Hou et al., 2010). One month later metamorphosis takes place, when snout-vent length is about 14.5 mm (Hou et al., 2010). Metamorphosed juveniles have been found in March (Chen & Lue, 1986), suggesting a reproductive pattern similar to that of the other Taiwanese Hynobius species.