The tiger snake (Notechis scutatus) is a large and highly venomous snake of southern Australia, including its coastal islands and Tasmania. These snakes are often observed and locally well known by their banding, black and yellow like a tiger, although the species can be highly variable in colouration and patterning. All populations are classified within the genus Notechis (Elapidae). Their diverse characteristics have been classified either as distinct species or by subspecies and regional variation. While tiger snakes are usually ground-dwelling, they are able to swim as well as climb into trees and buildings.
Taxonomy The genus Notechis is in the elapid family, venomous snakes with fixed front fangs. The classification of this genus is given as a single and highly variable species, Notechis scutatus, or a second species Notechis ater, and by an arrangement of subspecies or regional morphs. A 2016 genetic analysis showed that the closest relative of the tiger snakes is the rough-scaled snake (Tropidechis carinatus). The two extensively recognized species of this genus are Notechis scutatus (Peters, 1861) and Notechis ater (Krefft, 1866), which show further variety in their characteristics. Several authors have published revisions or described subspecies of these species. Others consider the names contained by this taxonomic arrangement to be unwarranted, and describe Notechis as a monotypic genus. Various authorities accept some or all the systematics previously applied, but most agree a revision of the genus is needed. 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 as N. ater humphreysi, (Warrell, 1963) and the Peninsula tiger snake as N. ater niger (Kinghorn 1921). Island populations of N. scutatus have evolved larger heads to cope with large prey animals. Young populations have larger heads by phenotypic plasticity, whereas large heads have become genetically assimilated in older populations.
* Not including the nominate subspecies (typical form).
Description
Notechis is a genus of large venomous snakes 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 colour. Individuals also show seasonal variation in colour. The total length is typically about 1.2 metres (3 ft 11 in) The patterning is darker bands, strongly contrasting or indistinct, which are pale to very dark in colour. Colouration is olive, yellow, orange-brown, or jet-black, and the underside of the snake is light yellow or orange. Tiger snakes use venom to kill prey, and may also bite an aggressor; they are potentially fatal to humans. Tolerant of low temperatures, the snake may be active on warmer nights. When threatened, they flatten their bodies and raise their heads above the ground in a classic prestrike stance.
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. Its body is capable of being flattened along its entire length when the snake is agitated or basking. Its average length is 0.9 m (2 ft 11 in), with a maximum length of 1.2 m (3 ft 11 in), but has been recorded at 2 m (6 ft 7 in). Highly variable in colour, its base colours are brown, grey olive, or green with lighter crossbands usually of creamy yellow. Occasionally, unbanded specimens are found. Scales appear like overlapping shields, especially around the neck. Ventral scales 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 head is distinct from its robust body, and grows to 2 m (6 ft 7 in) in length. Dorsally, it is steel-blue to black in color 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). The Chappell Island tiger snake has a blunt head distinct from a robust body. The giant of the tiger snakes species, it averages 1.9 m (over 6 ft) in length. Dorsally, its colour is 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.
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