The Eastern Brown Snake ( Pseudonaja textilis ), also known as the Common Brown Snake, is a highly venomous elapid snake native to eastern and central Australia and southern New Guinea. It is considered the world's second-most venomous land snake, after the inland taipan, and is responsible for the most snake-bite deaths in Australia. Despite its deadliness, the Eastern Brown Snake is not naturally aggressive towards humans. Most bites occur when humans attempt to handle or kill the snake. The simplest safety precaution is to leave the snake alone. Move away slowly and calmly and let it slither away on its own accord. Call a snake-catcher if necessary to remove it.
Identification and Physical Characteristics
First described in 1854 by André Marie Constant Duméril, Gabriel Bibron, and Auguste Duméril, the adult eastern brown snake has a slender build and can grow to 2 meters (7 ft) in length. Their coloration varies widely, ranging from pale brown or light brown to dark brown, depending on their age and location. The colour of its surface ranges from pale brown to black, while its underside is pale cream-yellow, often with orange or grey splotches. Eastern brown snakes from Merauke have tan to olive upperparts, while those from eastern Papua New Guinea are very dark grey-brown to blackish. Adult brown snakes typically have a uniform color, though some individuals may display a faint banding pattern. The snake's belly is usually cream, yellow, or pale orange with darker pink or orange blotches. Its body scales are smooth and slightly glossy.
The snake's medium-sized orange eyes have round black pupils below a prominent brow ridge. Like most snakes, it is deaf, has a forked tongue, and no eyelids. The tongue is dark. The iris is blackish with a paler yellow-brown or orange ring around the pupil. The snake's chin and under parts are cream or pale yellow, sometimes fading to brown or grey-brown towards the tail. Often, orange, brown, or dark grey blotches occur on the under parts, more prominent anteriorly. Juveniles can vary in markings, but generally have a black head, with a lighter brown snout and band behind, and a black nuchal band. Its yellowish under parts serve to distinguish it from the dugite (Pseudonaja affinis) and peninsula brown snake (P. inframacula), which are entirely brown or brown with grey under parts.
The eastern brown snake has 17 rows of dorsal scales at midbody, 192 to 231 ventral scales, 45 to 75 divided subcaudal scales (occasionally some of the anterior ones are undivided), and a divided anal scale. Its mouth is bordered by six supralabial scales above, and seven (rarely eight) sublabial scales below. Its nasal scale is almost always undivided, and rarely partly divided.
Habitat and Distribution
The eastern brown snake's distribution ranges from northern Queensland to South Australia, with isolated populations in the Barkly Tableland and the MacDonnell Ranges in the Northern Territory and the far east of the Kimberley in Western Australia, and discontinuously in parts of New Guinea, specifically northern Milne Bay Province and Central Province in Papua New Guinea, and the Merauke region of Papua Province, in the Indonesian part of New Guinea. They are common in southeastern Queensland between Ipswich and Beenleigh.
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They are absent from rainforests, alpine regions, and the island of Tasmania.
The eastern brown snake occupies a varied range of habitats from dry sclerophyll forests (eucalypt forests) and heaths of coastal ranges, through to savannah woodlands, inner grasslands, and arid scrublands and farmland, as well as drier areas that are intermittently flooded. It is more common in open habitat and also farmland and the outskirts of urban areas. The snake's diet of rodents may explain its affinity for areas close to human habitation.
Diet and Hunting Behavior
The eastern brown snake is a carnivorous reptile that primarily feeds on vertebrates, including frogs, lizards, birds, mammals, and eggs. However, since European settlement who introduced rabbits, rats and mice, these introduced animals have become a favourite delicacy for the snake. Larger snakes mostly eat warm-blooded animals, while the smaller ones prefer exothermic prey such as lizards. The eastern brown snake rarely eats during winter, and females rarely eat while pregnant with eggs.
The eastern brown snake hunts during the cooler daylight hours, relying primarily on sight to locate its prey. A foraging snake raises its head like a periscope every so often to survey the landscape for prey. Once spotted, the snake chases its victim at high speeds. These snakes generally find their food source in their refuges rather than chasing fleeing prey. Adults generally hunt during the day, while juveniles sometimes hunt at night.
Then, it kills its victim by injecting venom and, for larger prey, constricting and suffocating it. The eastern brown snake can dislocate its jaw and stretch its skin to swallow large prey. While most animals succumb to its venom, the breaded dragon lizard fights back and often escapes.
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Behavior and Reproduction
Eastern brown snakes are generally solitary, with females and younger males avoiding adult males. They are active during the day, though they may retire in the heat of hot days to come out again in the late afternoon. It is most active in spring, the males venturing out earlier in the season than females, and is sometimes active on warm winter days. The occasional nocturnal activity has been reported. At night, it retires to a crack in the soil or burrow that has been used by a House mouse. During winter, they hibernate, emerging on warm days to sunbathe.
Eastern brown snakes mate in mid to late spring. Males engage in ritual combat with other males for access to females. The appearance of two males wrestling has been likened to a plaited rope. The most dominant male mates with females in the area. Copulation can last up to two hours, and the female may store sperm for several weeks after mating.
The female lays a clutch of about 15 eggs and abandons the eggs. The size of hatchlings varies greatly, from 189-275mm and 4-10gm. All hatchlings have a common head banding but differ greatly in the patterns and bandings on their bodies. These markings fade as they mature. Hatchlings are independent from birth and acquire the distinctive threat display characteristic of their species within 15 minutes of hatching.
Venom and its Effects
The eastern brown snake's fangs are small compared to those of other Australian venomous snakes, averaging 2.8 mm (0.11 in) in length or up to 4 mm (0.16 in) in larger specimens, and are 11 mm (0.43 in) apart. Eastern brown snake venom is the second most potent snake venom in the world. Venom from an Eastern Brown snake bite can kill a human within 4 hours. Drop for drop, it is 12 times more deadly than an equivalent amount of Indian cobra venom.
Eastern brown snake venom contains fast-acting pre-synaptic neurotoxins, procoagulants, cardiotoxins and nephrotoxins that cause progressive paralysis, uncontrollable bleeding, respiratory failure and death. Because of its small fangs (about 3mm), the initial bite is painless and often difficult to detect. It can kill a human within 4 hours. Once symptoms appear, however, progression is very rapid, and death can be sudden and unexpected.
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Clinically, the venom of the eastern brown snake causes venom-induced consumption coagulopathy; a third of cases develop serious systemic envenoming including hypotension and collapse, thrombotic microangiopathy, severe haemorrhage, and cardiac arrest. Other common systemic symptoms include nausea and vomiting, diaphoresis (sweating), and abdominal pain. Acute kidney injury and seizures can also occur. The onset of symptoms can be rapid, with a headache developing in 15 minutes and clotting abnormalities within 30 minutes; collapse has been recorded as occurring as little as two minutes after being bitten. Death is due to cardiovascular causes such as cardiac arrest or intracranial haemorrhage. Often, little local reaction occurs at the site of the bite.
The eastern brown snake's venom contains coagulation factors VF5a and VF10, which together form the prothrombinase complex pseutarin-C. This cleaves prothrombin at two sites, converting it to thrombin. The venom also contains pre- and postsynaptic neurotoxins; textilotoxin is a presynaptic neurotoxin, at one stage considered the most potent recovered from any land snake.
Conservation Status and Threats
Eastern brown snakes are currently not considered endangered and are actually quite common throughout their range. According to IUCN, the Eastern brown snake is locally common and widespread throughout its range but no overall population estimate is available.
Animals that prey on the eastern brown snakes include birds of prey and feral cats. Large numbers of these snakes are also killed by humans. Most snake bites occur as a direct result of people trying to kill snakes.
Safety and First Aid
Despite it deadliness, the Eastern Brown Snake, it is not naturally aggressive towards humans. Most bites occur when humans attempt to handle or kill the snake. If approached, the snake will try to avoid detection or flee. However, if the snake feels threatened or is startled, it may react defensively and strike at any perceived threat, including humans.
When travelling through areas the snake is likely to inhabit, avoid going off the beaten track and into dense undergrowth.
Standard first-aid treatment for any suspected bite from a venomous snake is for a pressure bandage to be applied to the bite site. The victims should move as little as possible, and to be conveyed to a hospital or clinic, where they should be monitored for at least 24 hours. Tetanus toxoid is given, though the mainstay of treatment is the administration of the appropriate antivenom. Brown snake antivenom has been available since 1956.