Eastern brown snake

Appearance

Adult eastern brown snakes are highly variable in colour. Whilst usually a uniform shade of brown, they can have various patterns including speckles and bands, and range from a very pale fawn colour through to black, including orange, silver, yellow and grey. Juveniles can be banded and have a black head, with a lighter band behind, a black nape, and numerous red-brown spots on the belly.

This species has an average length of 1.1–1.8 m. The maximum recorded size for the species is 2.4 m, although any specimen of greater than 2 m in length would be considered exceptionally large. Large eastern brown snakes are often confused with "king brown" snakes, whose habitat they share in many areas.

Distribution

The eastern brown snake is found all the way along the East coast of Australia, from the tip of Cape York, along the coasts and inland ranges of Queensland, New South Wales, Victoria and South Australia. They are also found in arid areas of the Northern Territory, 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. Because their mainly rodent diet, they can often be found near houses and farms.

The snake occupies a varied range of habitats from dry sclerophyll forests and heaths of coastal ranges, through to savannah woodlands, inner grasslands and arid scrublands and farmland. It is not found in rainforests or other wet areas, nor is it found in very dry deserts with little or no cover.

Eastern brown snakes are increasing in number in urban areas, and are now frequently sighted in city suburbs. The suburbs of Brisbane and Sydney now contain significant populations of brown snakes and they are often seen in suburban backyards searching for rodents.

Behavior

The eastern brown snake is diurnal. It is notorious for its speed and aggression throughout its habitats. When highly agitated, they hold their necks high, appearing in an upright S-shape. The snake usually seeks to flee when confronted, though it can be highly aggressive if provoked and instances where snakes have pursued humans over distances of up to 100 meters have been observed. This species is attracted to rural and farming areas, probably due to the large numbers of associated rodents. Such areas also normally provide shelter in the form of rubbish and other cover.

Habitat

The eastern brown snake is found all the way along the East coast of Australia, from the tip of Cape York, along the coasts and inland ranges of Queensland, New South Wales, Victoria and South Australia. They are also found in arid areas of the Northern Territory, 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. Because their mainly rodent diet, they can often be found near houses and farms.

The snake occupies a varied range of habitats from dry sclerophyll forests and heaths of coastal ranges, through to savannah woodlands, inner grasslands and arid scrublands and farmland. It is not found in rainforests or other wet areas, nor is it found in very dry deserts with little or no cover.

Eastern brown snakes are increasing in number in urban areas, and are now frequently sighted in city suburbs. The suburbs of Brisbane and Sydney now contain significant populations of brown snakes and they are often seen in suburban backyards searching for rodents.

Reproduction

Eastern brown snakes mate during spring; they are oviparous. Males engage in 'ritual combat' with other males for control of territory. The most dominant male will mate with females in the area. The females produce a clutch of 10–40 eggs in late spring or early summer. They do not guard the nest after the eggs are laid — the juvenile snakes are totally independent of the mother.

Food

The main component of their diet is rodents, particularly introduced house mice. Frogs, small birds, eggs and even other snakes are also consumed.

Defense

The eastern brown snake is considered to be the second most venomous terrestrial snake. The venom has a SC LD50 range of 36.5 —53 μg/kg and consists mostly of neurotoxins and blood coagulants. These snakes kept at venom supply laboratories yield an average of 2—10 mg of venom per milking. Engelmann and Obst give a venom yield of 2 mg. As with most venomous snakes, the volume of venom produced is largely dependent on the size of the snake. Worrell reported a milking of 41.4 mg from a relatively large 2.1 metres specimen. This record is atypical, as the eastern brown snake yields a low volume of venom which is reported as not more than 10 mg, averaging only 2 mg.

Clinically, the venom of the eastern brown snake is known to cause diarrhea, dizziness, collapse or convulsions, renal failure, paralysis and cardiac arrest.
Without medical treatment, bites can be fatal. As this species tends to initiate their defence with non-fatal bites, the untreated mortality rate in most snakebite cases reported is 10–20%, which is not very high.