Tiger snake

For the African snake, see Telescopus semiannulatus.

Tiger snake
Notechis sp.
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Elapidae
Genus:	Notechis Boulenger, 1896[1]
Species:	Notechis scutatus Peters, 1861[2]

Tiger snakes are a type of venomous serpent found in southern regions of Australia, including its coastal islands and Tasmania. These snakes are highly variable in their colour, often banded like those on a tiger, and forms in their regional occurrences. All populations are in the genus Notechis, and their diverse characters have been described in further subdivisions of this group; they are sometimes described as distinct species and/or subspecies.

Description

A genus of large venomous snake in the family Elapidae restricted to subtropical and temperate regions of Australia. Tiger snakes are a large group of distinct populations, which may be isolated or overlapping, with extreme variance in size and color. Individuals also show seasonal variation in color. The total length can be up to 2.1 meters (7 ft).^[3] The patterning is darker bands, strongly contrasting or indistinct, which are pale to very dark in color. Coloration is composed of olive, yellow, orange-brown, or jet-black, the underside of the snake is lighter and yellow or orange. The tiger snake uses venom to dispatch their prey, and may bite an aggressor; they are potentially fatal to humans. Tolerant of low temperatures, the snake may be active on warmer nights.^[4] When threatened they will flatten their body and raise their head above the ground in a classic pre-strike stance.

Reproduction

Tiger snakes give birth to 12 to 40 live young, an exceptional record was made of 64 from an eastern female.^[4]

Morphs

The widely dispersed populations (sometimes referred as polymorphs) show some conformity in their descriptions, but these characters may be shared by separate or adjacent groups. Tiger snakes are also identified by the region or island in which the forms occur, which is prefixed to a common name.

The Common tiger snake has a flat blunt head, slightly distinct from a robust body. Body capable of being flattened along entire length when snake is agitated or basking. Average length 0.9 m, maximum length 1.2 m but has been recorded at 2.0 m (or ~6.6 ft). Highly variable in colour, with base colours of brown, grey olive, green with lighter crossbands usually of creamy yellow. Occasionally unbanded specimens are found. Scales appear like overlapping shields, especially around the neck. Ventrals number 140 to 190, subcaudals 35 to 65, mid-body in 17 or 19 rows and the anal scale is single.

The Western tiger snake has a head that is distinct from its robust body, and grows to 2.0 m in length. Dorsally, steel-blue to black with bright yellow bands; unbanded specimens occur. The ventral surface is yellow, tending black towards the tail. Midbody scales are in 17 or 19 rows, ventrals number 140 to 165, subcaudals 36 to 51 (single) and the anal scale is single (rarely divided).

Chappell Island tiger snake, shows fangs

The Chappell Island tiger snake has a blunt head distinct from a robust body. The giant of the tiger snakes species, averaging 1.9 m (over 6 feet) in length. Dorsally, olive-brown to almost black, sometimes with lighter crossbands. The ventral surface is usually lighter in colour. Juveniles are banded. Mid-body scales are in 17 rows; ventrals number 160 to 171, subcaudals 47 to 52 (single), and the anal scale is single. These snakes are quite docile.

The King Island and Tasmanian tiger snakes each have a blunt head distinct from a robust body. Younger snakes may be slimmer and similar to other tiger snakes, eventually growing up to 1.5 m in length. Dorsally, may be jet black, jet black with lighter crossbands, grey with black flecks forming faint bands or an unbanded grey or brown. The ventral surface is usually a lighter colour. Midbody scales are in 19, 17 or sometimes 15 rows, ventrals number 161 to 174, subcaudals 48 to 52 (single) and the anal scale is single. Tasmanian tiger snakes tend to be quiet snakes, probably due to the lower temperature range they inhabit.

The Peninsula tiger snake has a blunt head distinct from a robust body. Averages 1.1 m in length. Roxby Island specimens are much smaller, averaging 0.86 m in length. Dorsally, generally jet black, sometimes with white or cream markings around the lips and chin. On Kangaroo Island, specimens are highly variable in colour, often exhibiting banding and uniform brown colours. The ventral surface is dark grey to black, with some specimens on Kangaroo Island even possessing red bellies. The ventral surface becomes much lighter prior to shedding. Juveniles nearly always have banding. Mid-body scales are in 17, 18, 19 and rarely 21 rows, ventrals number 160 to 184, subcaudals 45 to 54 (single) and the anal scale is single.

The subspecies Notechis ater ater, found away from mainland Australia, is typically uniformly black.

As with most snakes, the colours vary widely between individuals and are an unreliable means of identifying subspecies. Accurate identification is best performed with a venom test kit or scale count.

Habitat

King Island tiger snake, with barely visible banding, near Petrified Forest on King Island, Australia

Tiger snakes are found in coastal environments, wetlands, and creeks where they often form territories. Areas with an abundance of prey can support large populations. The species' distribution extends from the south of Western Australia through to South Australia, Tasmania, up through Victoria, and New South Wales. Its common habitat includes the coastal areas of Australia.

Taxonomy

The genus Notechis is placed in the family of elapid snakes. There are two widely recognized species of this genus, Notechis scutatus (Peters, 1861) and Notechis ater (Krefft, 1866), which show further variety in their characteristics.^[1] Several authors have published revisions or described subspecies of these species.^[5] Others consider the names contained by this taxonomic arrangement to be unwarranted, and describe Notechis as a monotypic genus.^[4] Various authorities accept some or all the systematics previously applied but most agree that a revision of the genus is needed.^[5] Names for these subdivisions include the Western types, appended to both species names as occidentalis (Glauert 1948) The island groups have also been described as subspecies: Chappell Island tiger snake as N. ater serventyi (Warrell, 1963), King Island and Tasmanian tiger snakes subspecies N. ater humphreysi, (Warrell, 1963) and the Peninsula tiger snake N. ater niger( Kinghorn 1921).

Species

Species	Authority	Subsp.*	Common name	Geographic range
N. ater	Krefft, 1866	3	Black tiger snake	Australia (Western Australia, South Australia, Tasmania)
N. scutatus	Peters, 1861	1	Mainland tiger snake	Australia (New South Wales, Queensland, South Australia, Victoria, Western Australia)

* Not including the nominate subspecies (typical form).

Venom

Tiger snakes possess a potent neurotoxin, coagulants, haemolysins and myotoxins. Symptoms of a bite include localized pain in the foot and neck region, tingling, numbness, and sweating, followed by a fairly rapid onset of breathing difficulties and paralysis. In a study, the untreated mortality rate from its bites is reported to be between 40-60%.^{[6] [7]}

Treatment is the same for all Australian venomous snakes. The Pressure Immobilization Method (PIM) is used to inhibit the flow of venom through the lymphatic system. Broad thick bandages are applied over the bite, then down and back along the limb to the armpit or groin. The affected limb is then immobilized with a splint. Identification of the venom is possible if traces are left near the wound. Identifying the snake is not necessary if bitten in Tasmania, however, as the same antivenom is used to treat all Tasmanian snakes' bites. The availability of antivenom has greatly reduced the incidence of fatal tiger snake bites. The number of deaths is now exceeded by the brown snake.^[8]

Conservation

In most Australian states they are protected species, and to kill or injure one incurs a fine of up to $7,500 as well as a jail sentence of 18 months in some states ("National Parks and wildlife Act (SA)". Parliament of SA. 2009. http://www.legislation.sa.gov.au/lz/c/a/national%20parks%20and%20wildlife%20act%201972/current/1972.56.un.pdf. Retrieved 2009-04-23. ) . It is also illegal to export a native Australian snake.

Gallery

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  Mainland tiger snake Banyule Flats Reserve. Melbourne, VIC.

References

1. ^ ^{a b} "Notechis". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=700234. Retrieved 23 March 2008. 
2. ^ Species Notechis scutatus at The Reptile Database
3. ^ Kindersley, Dorling (2001,2005). Animal. New York City: DK Publishing. ISBN 0-7894-7764-5. 
4. ^ ^{a b c} Browne-Cooper, R., Bush, B., Maryan, B., Robinson, D. (2007). Reptiles and Frogs in the Bush: Southwestern Australia. University of Western Australia Press. pp. 254, 255. ISBN 9778 1 920694 74 6. 
5. ^ ^{a b} Genus Notechis at The Reptile Database
6. ^ University of Adelaide Clinical Toxinology Resource
7. ^ Brent W. Burkhart; Phillips Donovan (2005). "Critical Care Toxicology: Diagnosis and Management of the Critically Poisoned Patient". Toxicological diagnosis and management of envenomated patients (Mosby). 
8. ^ Chris Thompson; Dr. Struan K. Sutherland (November 2003). "Australian Snake Bites". Envenomation in Australia. University of Sydney. http://www.usyd.edu.au/anaes/venom/snakebite.html. Retrieved 2008-03-23. 

External links

• video of Mainland Tiger snakes
• Information on bites from survivaliq.com
• Information on the genus from snakeshow.net
• Integrated Taxonomic Information System - Notechis