Ahaetulla nasuta

Ahaetulla nasuta, also known as Sri Lankan green vine snake and long-nosed whip snake, is a venomous, slender green tree snake endemic to Sri Lanka.

Etymology
The genus name Ahaetulla comes from the Sri Lankan Sinhalese words ahaetulla/ahata gulla/as gulla, meaning “eye plucker” or “eye picker”, because of the belief that they pluck out the eyes of humans, as first reported by the Portuguese traveler João Ribeiro in 1685. The species name nasuta is Latin for "of the nose", in reference to its elongated snout.

Vernacular names
The Sinhala name "Aheatulla" or "eye-plucker" forms the taxonic genus name. In Tamil, it is known as pachai paambu. In Kannada, it is known as Hasiru Haavu.


 * Sinhala: ඇහැටුල්ලා (Pronounced: Aheatulla)
 * Tamil: பச்சை பாம்பு
 * Kannada: ಹಸಿರು ಹಾವು
 * Marathi: हरणटोळ (Pronounced: harantol)
 * West Bengal: লাউডগা ( Pronounced:Laudoga)

Distribution and Taxonomy
Due to longstanding confusion over the taxonomy of A. nasuta, the species was once thought to have a large range from Sri Lanka to peninsular India, including the Western Ghats, along with a disjunct population in Southeast Asia. Recent phylogenetic studies have since found the species to be paraphyletic, and in need of taxonomic revision.

A 2017 study reclassified the former subspecies Ahaetulla nasuta anomala as a distinct species, Ahaetulla anomala, although a 2020 study later found A. anomala to be possibly conspecific with Ahaetulla oxyrhyncha.

The cladogram below from a 2019 study shows Ahaetulla nasuta as paraphyletic:

A 2020 phylogenetic study reaffirmed the paraphyletic nature of A. nasuta, and found it to actually comprise a species complex, with the "true" A. nasuta (from which the species was originally described) being restricted to the wet zone of Sri Lanka (including the Sri Lanka lowland and montane rainforests). Four populations from the Western Ghats of India that were formerly grouped with A. nasuta were split into the species A. borealis, A. farnsworthi, A. isabellina, and A. malabarica. The large-bodied form from lowland peninsular India (and possibly the dry zone of the northern portion of Sri Lanka), which was also formerly grouped with A. nasuta, was found to actually be A. oxyrhyncha, and is actually more closely allied with A. pulverulenta and A. sahyadrensis than A. nasuta. Finally, the disjunct population in Southeast Asia was assigned to an as-of-yet undescribed species, tentatively referred to as Ahaetulla cf. fusca, and is a sister species to Ahaetulla laudankia.

Habitat
It is found in low bushes, shrubs and trees in lowland forest terrain at elevations up to about 1000 metres, particularly near streams and often found near human settlements.

Description
Common vine snakes are diurnal, arboreal, and mildly venomous. They normally feed on frogs and lizards using their binocular vision to hunt. They are slow moving, relying on camouflaging themselves as vines in foliage. They expand their bodies when disturbed to show a black and white scale marking. Also, they may open their mouths in a threat display and point their heads in the direction of the perceived threat. They are the only species of snake with horizontal pupils, compared to the normal vertical slit pupils found in many species of viper.

Taxonomic description
The following description with diagnostic characters is from Boulenger (1890): "Snout pointed, terminating in a dermal appendage, which is shorter than the eye and formed entirely by the rostral; the length of the snout, without the appendage, about twice the diameter of the eye or rather more. No loreal; internasals and prefrontals in contact with the labials; frontal as long as its distance from the rostral or a little longer, as long as the parietals or a little longer; two preoculars and a small subocular (or one preocular and two suboculars), upper preocular in contact with the frontal; two postoculars; temporals 1+2 or 2+2; upper labials 8, fifth entering the eye; 4 lower labials in contact with the anterior chin-shields, which are shorter than the posterior. Scales in 15 rows. Ventrals 172–188; anal divided; subcaudals 140–166. Bright green or pale brownish, the interstitial skin between the scales black and white on the anterior part of the body, which appears striped when distended; a yellow line along each side of the lower surface. Total length 5 feet: tail 2."

Behavior
They feed on lizards and other invertebrates. The species is ovoviviparous, giving birth to young that grow within the body of the mother, enclosed within the egg membrane. They may be capable of delayed fertilization; (parthenogenesis is rare but not unknown in snakes) as a female in the London zoo kept in isolation from August, 1885 gave birth in August, 1888.

Venom and its effects
The components of its venom are unknown.

Bites from this species produce a moderate reaction in humans, causing localized pain, swelling, bruising, and numbness that typically resolves within 72 hours. Any bite near the vital organs should be considered a medical emergency.