Tiger snakes
Tiger snakes are found in the temperate areas of southern Australia, including Tasmania where they are particularly large and venomous. Identification of tiger snakes by the presence of stripes is unreliable, since this varies with the seasons and the maturity of the snake and there is an unstriped black species (Notechis ater). Also several other venomous and non-venomous Australian snakes are striped. Features of tiger snake envenomation include neurotoxicity (caused by pre-synaptic and post-synaptic neurotoxins), coagulopathy and rhabdomyolysis.
Mainland Tiger Snake (Notechis scutatus) This snake is distributed along the southeastern coast of Australia, including many of the most populous areas in Victoria, eastern New South Wales and parts of South Australia. Therefore their bite is currently one of the most common snake bite in Australia. Mainland tiger snakes are active on warm summer evenings. They are attracted to farms and outer suburban houses, where they hunt mice and rats. This makes them easily trodden on at night by unwary barefoot people. They are also found in swampy or marshy grounds, around creeks, rivers or dams where they hunt frogs . Tiger snakes are ovoviviparous (holding the eggs in their abdomen until they hatch, and giving birth to live young). The average litter size is around 30.
Mainland tiger snakes are solidly built, with broad, flattened heads. When disturbed they may flatten their necks in a threat display and usually strike low to the ground. Average length is approximately 1m. Adults are usually banded and colour may vary from pale yellow to almost black. Occasionally, the bands may be absent, leading to difficulties with identification. The fangs are usually around 3.5-5mm in length. The venom is produced in large quantities with an average yield of around 35mg. The record yield was 180mg. Tiger snake venom contains pre-synaptic and post-synaptic neurotoxins, myotoxins and procoagulants. Bites result in paralysis, incoagulable blood and muscle damage, which may lead to renal failure.
Black Tiger Snakes (Notechis ater) or Island Tiger Snakes These species of tiger snake are quite distinct from mainland tiger snakes. Most live on islands off the south coast of Australia and Tasmania, although some have a limited range on the mainland. The Black tiger snakes (N. ater occidentalis) are found in the southwest corner of Western Australia. The Krefft's tiger snakes (N. ater ater) live in a small area of the Flinders Ranges in South Australia. Peninsula tiger snakes (N. ater niger) are found on the Yorke and Ayre Peninsula and Kangaroo Island and neighbouring islands. N. ater humphreysi is found on King island and most of the Bass Strait islands. The large N. ater serventyi is found on Chappell Island and Badger Island. Most black tiger snakes prefer marshy areas, and are active in the day. Offshore Island tiger snakes eat mostly mutton birds, and often use their burrows.
N. ater are usually black, with paler abdomens. Banding is sometimes seen in Western Australian subspecies, but is uncommon in other subspecies. Size is highly variable. Chappell island tiger snakes are generally the largest and may reach 2.4m. Krefft's tiger snake rarely exceeds 0.9m. Young black tiger sakes are born alive. Litters vary from 20 to 30.
The Chappell Island tiger snake is the most prolific venom producer of all the black tiger snakes. It has an average yield of 74mg with a maximum recorded yield of 388mg. Victims of envenomation by this snake should initially be treated with double the usual dose of antivenom, due to the copious amounts of venom produced. The toxicity of Chappell Island tiger snakes is less than that of the mainland tiger snakes. The South Australian Island tiger have a similar venom yield to those of the mainland (yield of 34mg). The components of the venom are similar to those of the mainland tiger snakes, causing paralysis, clotting deficits and muscle damage. Tigersnake or polyvalent antivenom is used to treat this envenomation.
