|Distribution of Oxyuranus scutellatus in green|
The coastal taipan (Oxyuranus scutellatus), or common taipan, is a species of highly venomous snake in the family Elapidae. Described by Wilhelm Peters in 1867, the species is native to the coastal regions of northern and eastern Australia and the island of New Guinea. The second longest venomous snake in Australia, the coastal taipan averages around 2 m (6.6 ft) long, with the longest specimens reaching 2.9 m (9.5 ft) in length. It has light olive or reddish-brown upperparts, with paler underparts. The snake is considered to be a least-concern species according to the International Union for Conservation of Nature (IUCN).
The coastal taipan is found in a wide range of habitats, from monsoon forests to open woodland, as well as human-modified habitats such as sugar cane fields. It mainly hunts and eats small mammals, as well as opportunistically taking bird victims. The species is oviparous.
According to most toxicological studies, this species is the third-most venomous land snake in the world after the inland taipan and eastern brown snake. Its venom is predominantly neurotoxic and coagulopathic.
German naturalist Wilhelm Peters described the coastal taipan as Pseudechis scutellatus in 1867, from material collected in Rockhampton, Queensland. Charles Walter De Vis described Pseudechis wilesmithii from Walsh River in north Queensland in 1911. Australian naturalist Roy Kinghorn established the genus Oxyuranus in 1923, describing a specimen from Coen in far north Queensland as O. maclennani after its collector, W. Maclennan.He noted the distinctness of the palatine bone necessitated the new genus as distinct from all other elapid snakes.
Australian herpetologist Ken Slater described Oxyuranus scutellatus canni, commonly known as the Papuan Taipan, in 1956, on the basis of its distinctive coloration. He named it after George Cann, longtime Snake Man of La Perouse. It is found throughout the southern portion of the island of New Guinea Raymond Hoser described Oxyuranus scutellatus barringeri from a specimen collected from the Mitchell Plateau, however Wolfgang Wüster declared this a nomen nudum as the author did not explain how it was distinct. Hoser replied that it was distinct on the basis of DNA and distribution, and published it under a different subspecific name—O. scutellatus andrewwilsoni—in 2009, reporting it had a more rounded head and rougher neck scales than other subspecies of coastal taipan, and lacked a lighter colour on the snout.
In Australia, the species is commonly called the coastal taipan, common taipan or simply taipan. The New Guinea subspecies is known as the Papuan taipan. Local names in New Guinea include Dirioro by the people of Parama village near the Fly River, and Gobari near the Vailala River.
The coastal taipan is the second longest venomous snake in Australia after the king brown snake (Pseudechis australis). Adult specimens of this species typically attain sexual maturity around 1.2 m (3.9 ft) in total length (including tail). More mature specimens can grow to between 1.5 and 2.0 m (4.9 and 6.6 ft). Other taipans, including the inland taipan, attain broadly similar sizes although they tend to be slightly smaller in average size. A specimen of an average 2 m (6.6 ft) total length weighs around 3 kg (6.6 lb). According to the Queensland Museum, the longest recorded total length for the coastal taipan was a specimen that was 2.9 m (9.5 ft) and weighed 6.5 kg (14 lb). However, though exceptionally rare, much larger specimens are widely believed to exist, including specimens of as much as 3.3 m (11 ft).
The head of the coastal taipan is long and narrow like that of the African black mamba (Dendroaspis polylepis), but without the "coffin" shape. The two species are strongly convergent in several aspects of morphology, ecology and behaviour. O. scutellatus has an angular brow and is lighter-coloured on the face. The body is slender and colouration can vary. It is often uniformly light olive or reddish-brown in colour, but some specimens may be dark gray to black. The colouration is lighter on the sides of the body, and the ventral side (the belly) is usually a creamy-white to a pale light yellow in colour, and is often marked with orange or pink flecks. Individuals undergo a seasonal change in colour, becoming darker in winter and fading in summer. The eyes are large, round, and are light brown or even hazel in colour with large pupils.
As a large brownish snake, the coastal taipan resembles the eastern brown snake (Pseudonaja textilis), northern brown snake (P. nuchalis), and king brown snake, though can be distinguished by its larger head and narrow neck, and light face and snout. The head and neck are the same width in the other species.
The number and arrangement of scales on a snake's body are key elements of identification to species level. The temporals are 2+3 (3+4). The dorsal scales are in 21–23 rows at mid-body. The ventrals number 220–250. The anal plate is single (undivided). The subcaudals number 45–80 and are divided. The scalation helps distinguish it from the king brown snake, which has a divided anal plate and 17 dorsal scales.
Distribution and habitat
The coastal taipan occurs in Australia and the southern New Guinea. Its range extends from north-western Western Australia, the Northern Territory, across Cape York Peninsula and down eastern Queensland into northern New South Wales (as far south as Grafton). However, the coastal taipan is not found in regions where the maximum winter temperature is below 20 °C (68 °F). The second subspecies (Oxyuranus scutellatus canni ) is found throughout the island of New Guinea, with higher concentrations of the snake being found in the nation of Papua New Guinea.
The coastal taipan can be found in a variety of different habitats. It can be found in warm, wetter temperate to tropical coastal regions, in monsoon forests, wet and dry sclerophyll forests and woodlands, and in natural and artificial grassy areas, including grazing paddocks and disused rubbish tips. In Queensland, it has adapted well to sugarcane fields, where it thrives on the rodent population in the fields. In Far North Queensland in the Cape York Peninsula, it is usually found in open woodland areas. Thickets of introduced Lantana are also favoured habitat. The coastal taipan shelters in abandoned animal burrows, hollow logs, and in piles of vegetation and litter.
The coastal taipan is primarily diurnal, being mostly active in the early to mid-morning period, although it may become nocturnal in hot weather conditions.
The coastal taipan is oviparous.
The coastal taipan's diet consists predominantly of rats, mice, and bandicoots, with various species of birds taken opportunistically. In 2010, a dead coastal taipan was found to have ingested a cane toad. It was unclear whether the snake had been poisoned by the toad and died, or had resisted the poison and been killed by a vehicle (as it was found on a road with neck trauma).
When hunting, it appears to actively scan for prey using its well-developed eyesight, and is often seen traveling with its head raised slightly above ground level. Once prey is detected, the snake "freezes" before hurling itself forward and issuing several quick bites. The prey is released and allowed to stagger away. This strategy minimizes the snake's chance of being harmed in retaliation, particularly by rats, which can inflict lethal damage with their long incisors and claws. It is not a confrontational snake and will seek to escape any threat. When cornered, though, it can become very aggressive and may strike repeatedly.
Classified as a snake of medical importance by the World Health Organization,[a] the coastal taipan is considered the second-most venomous terrestrial snake in the world, behind the inland taipan and eastern brown snake. Coastal taipans were responsible for 4% (31 cases) of identified snakebite victims in Australia between 2005 and 2015, though no deaths were recorded in this cohort. At least one death from this species was recorded in a coronial retrospective study of snakebites from 2000 to 2016, and two between 1981 and 1991. Bites from the coastal taipan account for most snakebites in New Guinea in the rainy season, when the snake becomes more active, particularly in southern parts of the island.
Clinically, envenomation from coastal taipan bites commonly leads to neurotoxic effects, characterised by descending flaccid paralysis, ptosis, diplopia, ophthalmoplegia, bulbar weakness, intercostal weakness and limb weakness. Severe cases require intubation. Venom-induced consumption coagulopathy is also common, characterised by clotting abnormalities and haemorrhage. Less common effects are muscle damage (myotoxicity), characterised by elevated creatine kinase and myalgia (muscle pain), acute kidney injury (which can require dialysis in severe cases), as well as general systemic symptoms such as nausea and vomiting, diaphoresis (sweating), and abdominal pain. White cell count is commonly elevated and platelet count is often low. There is generally little local reaction at the site of the bite.
The SC LD50 value of this species is 0.106 mg/kg, according to Australian Venom and Toxin database, and 0.12 mg/kg, according to Engelmann and Obst (1981). The average venom yield per bite is 120 mg, with a maximum record of 400 mg. The venom contains Taipoxin, which has an LD50 of 2 μg/kg, meaning 124 μg can kill a healthy 62 kg adult.
In cases of severe envenomation, death can occur as early as 30 minutes after being bitten, but the average is around 2.5 hours. The time between a bite and death depends on various factors such as the nature of the bite and the constitution of the victim. Untreated bites have a mortality rate of 100% as the coastal taipan always delivers a fatal dose of venom (an average bite delivers 10–12× the lethal dose of venom for a human adult male), and medical professionals recommend that victims seek immediate medical attention even for apparently minor bites. Before the introduction of specific antivenom by the Commonwealth Serum Laboratories in 1956, nearly all bites were fatal.
In his book Venom, which explores the development of a taipan antivenom in Australia in the 1940s and 1950s, author Brendan James Murray argues that only one person is known to have survived an Oxyuranus bite without antivenom: George Rosendale, a Guugu Yimithirr man bitten at Hope Vale in 1949. Murray writes that Rosendale's condition was so severe that nurses later showed him extracted samples of his own blood that were completely black in colour. A coastal taipan named Cyclone once gave 4.54 ml of wet venom straight out of the fangs.
Early administration (within 2–6 hours of bite) of antivenom and intubation for respiratory paralysis are keystones of management. However, there is a chance of a hypersensivity reaction following antivenom administration. Neurotoxic symptoms may be irreversible once established due to the presynaptic nature of their pathology.
The first taipan-specific antivenom was developed in 1954. Before this, tiger snake antivenom was used, though it was of little benefit in taipan envenoming.
Conservation and threats
- Snakes of medical importance include those with highly dangerous venom resulting in high rates of morbidity and mortality, or those that are common agents in snakebite.
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|Wikispecies has information related to Oxyuranus scutellatus.|
|Wikimedia Commons has media related to Oxyuranus scutellatus.|
- Barnett, Brian (1999). "Keeping and Breeding the Coastal Taipan (Oxyuranus scutellatus)". Journal of the Victorian Herpetological Society 10 (2/3): 38–45.
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