''Achalinus formosanus'', common name Formosan odd-scaled snake or Taiwan burrowing snake, is a non-venomous snake in family

Xenodermidae Xenodermidae is a family of snakes native to East Asia, South Asia, and Southeast Asia. All species in the family Xenodermidae are small or moderately sized snakes, never more than but typically less than in total length (including tail). ...

In earlier classifications sometimes still in use, subfamily

Xenodermatinae Colubridae (, commonly known as colubrids , from la, coluber, 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest species of the family date back to the Oligocene epoch. Colubrid snakes are found on ev ...

, family

Colubridae Colubridae (, commonly known as colubrids , from la, coluber, 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest species of the family date back to the Oligocene epoch. Colubrid snakes are found on ev ...

. See e.g. that is found in

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the northe ...

and in the southern

Ryukyu Islands The , also known as the or the , are a chain of Japanese islands that stretch southwest from Kyushu to Taiwan: the Ōsumi, Tokara, Amami, Okinawa, and Sakishima Islands (further divided into the Miyako and Yaeyama Islands), with Yona ...

(Japan).

Taxonomy

There are two subspecies: * ''Achalinus formosanus formosanus'' Boulenger, 1908 — Taiwan * ''Achalinus formosanus chigirai'' Ota and Toyama, 1989 — Ryukyu Islands Specific name ''formosanus'' means "from Formosa", referring to the fact that this species was first described from a specimen from Taiwan. ''chigirai'' refers to Yoshinori Chigira, who collected the first specimen of ''Achalinus formosanus chigirai''. ''Achalinus formosanus formosanus'' is ecologically and morphologically similar to the Taiwan

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...

'' Achalinus niger''; the two differ in some scale counts and characteristics. A study using genetic markers found these two taxa to be overlapping, warranting further studies on their taxonomy.

Distribution

''Achalinus formosanus formosanus'' is known from central and southern Taiwan at elevations of

asl American Sign Language (ASL) is a natural language that serves as the predominant sign language of Deaf communities in the United States of America and most of Anglophone Canada. ASL is a complete and organized visual language that is express ...

. ''Achalinus formosanus chigirai'' occurs at low altitudes (below ) on the

Iriomote-jima is the largest of the Yaeyama Islands of Japan, and the second largest in Okinawa Prefecture after Okinawa Island itself. The island has an area of and a 2005 population of 2,347. The island does not have an airstrip, and most visitors — o ...

and

Ishigaki Island , also known as ''Ishigakijima'', is a Japanese island south-west of Okinawa Hontō and the second-largest island of the Yaeyama Island group, behind Iriomote Island. It is located approximately south-west of Okinawa Hontō. It is within the ...

s, both belonging to the

Yaeyama Group Yaeyama may refer to: * Yaeyama Islands, an archipelago in Okinawa Prefecture, Japan * Yaeyama District, Okinawa, an administrative division covering most of the Yaeyama Islands * Yaeyama language The Yaeyama language (, ''Yaimamuni'') is a Sou ...

Description

Achalinus formosanus formosanus close-up with tongue extended

''Achalinus formosanus'' is a small snake growing to a total length of about . The whole body is iridescent under light. Head is small, oval, and without distinct neck. Body is slender and tail is moderately short. Eyes are small, bead-like;

iris Iris most often refers to: *Iris (anatomy), part of the eye *Iris (mythology), a Greek goddess * ''Iris'' (plant), a genus of flowering plants * Iris (color), an ambiguous color term Iris or IRIS may also refer to: Arts and media Fictional ent ...

is black and indistinct. Upper head, body and tail is uniform olive, grayish tan, or black. Mid-dorsal row of scales on body and tail show a dark longitudinal line. Ventral surface is olive-yellow or dark gray. The young are usually black.

Behaviour

It is a nocturnal, terrestrial snake that probably preys on earthworms, slugs, and frogs. It is non-venomous and not aggressive. It is

oviparous Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), a ...

Habitat and conservation

''Achalinus formosanus formosanus'' are found in montane humid forests, where they live in dark, wet micro-habitats such as the forest floor, rotten wood, and leaf litter. ''Achalinus formosanus chigirai'' have been collected in on a road at night and in a limestone cave in the daytime as well as in low grass along a path in the evening and on forest floor at night. No significant threats are known. It is not a protected species in Taiwan, but ''Achalinus formosanus chigirai'' is classified as "near threatened" in Japan.

References

{{Taxonbar, from=Q2822985 Xenodermidae Snakes of Asia Reptiles of Japan Reptiles of Taiwan Reptiles described in 1908 Taxa named by George Albert Boulenger