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.
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.[1] The species name nasuta is Latin for "of the nose", in reference to its elongated snout.[2] [3]
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.
In Western internet culture, the vine snake has occasionally been humorously nicknamed as the “judgmental shoelace”, due to their long, slender bodies and the horizontal shape of their pupils resembling a person narrowing their eyes in a captious expression.
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,[4] although a 2020 study later found A. anomala to be possibly conspecific with Ahaetulla oxyrhyncha.[5]
The cladogram below from a 2019 study shows Ahaetulla nasuta as paraphyletic:[6]
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.[5]
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.[7]
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.[8]
The following description with diagnostic characters is from Boulenger (1890):[9]
They feed on lizards and other invertebrates.[2] 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.[10]
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.[11] [12]