Tiger Snake (Notechis scutatus) – Sunshine Coast, Queensland

Tiger Snake (Notechis scutatus)

Tiger Snake (Notechis scutatus)
Matt Summerville
Sunshine Coast, Queensland

Also known ascommon tiger snake
Found: along the south-eastern coast of Australia, from New South Wales and Victoria to Tasmania and the far corner of South Australia

Mainland tiger snakes are responsible for the second-highest number of bites in Australia, as they inhabit highly populated areas along the east coast, including some metropolitan areas of Melbourne. They are attracted to farms and outer suburban houses, where they hunt mice nocturnally and can easily be trodden on by unsuspecting victims in the darkness.

Bites are fatal if untreated, causing pain in the feet and neck, tingling, numbness and sweating, followed by breathing difficulties and paralysis. The venom also damages the blood and muscles, leading to renal failure.

Adult snakes are usually (but not always) banded, with ragged stripes varying in colour from pale yellow to black along a solid, muscular body that can grow to 2m. When threatened, they flatten their necks and strike low to the ground. https://www.australiangeographic.com.au/topics/science-environment/2012/07/australias-10-most-dangerous-snakes/

Most Australians know of tiger snakes and are aware of their fearsome reputation, though few people will ever encounter one. Unfortunately this species is much maligned because of its aggressive nature and toxic venom; however the tiger snake should be recognised as a great survivor, superbly adapted to some of the most inhospitable environments in Australia.

Habitat

The species is often associated with watery environments such as creeks, dams, drains, lagoons, wetlands and swamps. They can also occur in highly degraded areas e.g. grazing lands, especially where there is water and local cover. Tiger snakes will shelter in or under fallen timber, in deep matted vegetation and in disused animal burrows. Unlike most other Australian elapids, tiger snakes climb well on both vegetation and human constructions, and have been found as high as 10 m above the ground.

Altitudinally, tiger snakes range from sea level to above 1000m (Tasmania).

Identification

In the past, two species of tiger snakes were commonly recognised: the Eastern Tiger Snake Notechis scutatus, and the so-called Black Tiger Snake Notechis ater. However, morphological differences between the two appear inconsistent, and recent molecular studies have shown N. ater and N. scutatus to be genetically similar, hence it would seem that there is now just one wide-ranging species that varies greatly in size and colouration – Notechis scutatus.

Despite this recent revision, the old classification is still in popular use and a number of subspecies are also recognised:

  • Notechis ater ater – Krefft’s Tiger Snake (Flinders Ranges, South Australia)
  • Notechis ater humphreysi – Tasmanian Tiger Snake (King Is. and Tasmania)
  • Notechis ater niger – Peninsular Tiger Snake (lower Eyre and Yorke Peninsulas, offshore islands of South Australia)
  • Notechis ater serventyi – Chappell Island Tiger Snake (Furneaux Group, Bass Strait)
  • Notechis scutatus occidentalis (sometimes N. ater occidentalis) – Western Tiger Snake (southwest corner of Western Australia)
  • Notechis scutatus scutatus – Eastern Tiger Snake (southeastern mainland Australia)

The common name refers to the prominent yellow and black cross-bands typical of some populations of tiger snakes, however not all have this pattern. The most commonly seen form is dark olive brown to blackish-brown, with off-white to yellowish cross-bands that can vary in thickness. Entirely patternless individuals may occur in banded populations, and these types range in colour from yellowish-brown to black. Some populations consist of almost entirely unbanded individuals, e.g. those of the central highlands and southwest of Tasmania. Melanism (dark body colouration) is most strongly developed in populations exposed to highly variable weather conditions and cool extremes, such as those experienced at higher altitudes or on offshore islands. The dark colouration is an adaptation that allows those snakes to absorb heat at a faster rate during the short growing season.
The head is moderately wide and deep and only slightly distinct from the robust, muscular body. The neck and upper body can be flattened to a considerable degree when performing a threat display, exposing the black skin between the relatively large, semi-glossy scales.

Midbody scales 17-21 rows, ventral scales 140-190, single anal and subcaudal scales. A large squarish frontal shield, not or scarcely longer than broad, is characteristic of Notechis.

Predators

The known predators of tiger snakes include the elapid snake Cryptophis nigrescensand certain birds of prey such as butcherbirds, goshawks, harriers, ibises, kites and kookaburras. In one survey taken on Carnac Island, a high proportion of the tiger snakes were blind in one (6.7 percent) or both eyes (7.0 percent) due the attacks by nesting gulls. While this is not predation per se, it does increase the catchability of the snakes by human hunters and hence probably increases the chances of their being taken by non-human predators. Tiger snakes have also been heavily persecuted by humans in the past and are still routinely killed when encountered. Many also become road victims.

Tiger snake are known to be parasitized by ticks, cestodes (tape worms), nematodes (round worms), pentastomids (tongue worms), and trematodes (flukes).

Danger to humans

The snake’s large size, often aggressive defence and toxic venom make it extremely dangerous to humans. Although generally shy and preferring escape over conflict, a cornered tiger snake will put on an impressive threat display by holding its forebody in a tense, loose curve with the head slightly raised and pointed at the offender. It will hiss loudly as it inflates and deflates its body, and if provoked further will lash out and bite forcefully. The venom of the tiger snake is strongly neurotoxic and coagulant, and anyone suspected of being bitten should seek medical attention immediately.

Evolutionary relationships

The present-day fragmented distribution of tiger snakes is due to a combination of geologically recent climatic changes (increasing aridity) and sea-level changes (islands cut off from the mainland in the past 6000-10000 years). Populations isolated through these events have undergone changes in their colour patterns, size and ecology in response to various environmental pressures. https://australianmuseum.net.au/learn/animals/reptiles/tiger-snake/

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