Inland Taipan (Oxyuranus microlepidotus): Facts and Venom

Appearance

The inland taipan is a robust snake with a deep, rather rectangular head, a rounded snout and smooth, glossy scales. Its body color ranges from pale fawn or straw yellow through olive and light greenish brown to rich dark brown. Many of the scales on its back have dark edges, and because the scales lie in diagonal rows, these edges line up into a broken herringbone or chevron pattern along the body.

The head and neck are usually several shades darker than the body: glossy black in winter and dark brown in summer. The belly is yellowish with orange blotches, and the color often creeps up onto the lowest scales of the flanks. The eyes are fairly large, with a very dark iris and a round pupil, which is typical of Australia’s elapids, the family that also includes cobras, mambas, coral snakes and sea snakes.

The most remarkable feature is that the whole snake changes shade with the seasons, becoming darker in the cool months and fading in the hot ones. Read more in why does the inland taipan change color?

Size

Adult inland taipans usually measure about 1.5 to 2 m (5 to 6.6 ft), with an average of about 1.8 m (5.9 ft). Large individuals reach about 2.5 m (8.2 ft). That makes it a big snake by Australian standards, though a little smaller on average than its relative the coastal taipan.

Weights are rarely published. Field researchers note that the snakes become sleek and plump when their main prey is abundant and grow thin during long droughts. Hatchlings are about 47 cm (18.5 in) long. The fangs are short for such a dangerous snake, about 3.5 to 6.2 mm (0.14 to 0.24 in).

Habitat and range

The inland taipan lives in the semi-arid Channel Country of central-east Australia, near the border of southwestern Queensland and northeastern South Australia. This is a vast region of braided river channels, such as the Diamantina River and Cooper Creek, that flood only occasionally. Records come from places such as Diamantina National Park, Goyder Lagoon, the Sturt Stony Desert and the Innamincka area, with an isolated population known near Coober Pedy.

Its key habitat is cracking clay. When the floodplains dry out, the heavy soil shrinks and splits into a network of deep cracks and holes. These cracks give the snake shelter from the extreme heat and cold and lead it straight to the burrows of its prey. It also ventures onto nearby gibber plains (stony desert covered in pebbles), sand dunes and rocky outcrops where there is cover. Vegetation is sparse: low saltbush and other chenopod shrubs, lignum, grasses and a few eucalypts along the channels.

Two specimens were collected in 1879 at the junction of the Murray and Darling Rivers in northwestern Victoria, and another near Bourke, New South Wales, in 1882. The species has never been found in either state since, and both list it as presumed or regionally extinct.

Diet and hunting

The inland taipan is a specialist hunter of mammals. In the wild its main prey is the long-haired rat (Rattus villosissimus), along with the plains rat, the introduced house mouse and small carnivorous marsupials known as dasyurids. Unlike most snakes, it seems to eat almost nothing else.

It hunts mostly underground or at burrow entrances. The snake corners a rat in a burrow or soil crack and bites it several times in quick succession, sometimes up to eight times, often holding on and pressing against the prey with its body. Most venomous snakes strike and let go to avoid being bitten back, then follow the scent trail. The inland taipan’s venom acts so fast that the prey has almost no chance to fight, so the snake can afford to hold on.

This explains why its venom is so potent against mammals. A rat trapped in a tight tunnel can bite back hard, so a venom that stops it within moments is a big advantage. The long-haired rat also goes through boom-and-bust cycles, breeding to plague numbers after good rains and almost vanishing in droughts, so the snakes feast in some years and live on fat reserves in others.

Venom

Inland taipan venom is the most toxic of any snake when tested in mice. Its subcutaneous LD50 (the dose that kills half of the test mice when injected under the skin) is about 0.025 mg per kilogram of body weight. That is roughly twice as potent as the eastern brown snake and many times more potent than cobras or rattlesnakes. An average bite delivers about 44 mg of venom, and the largest recorded yield is about 110 mg.

The venom is a cocktail. Its most important parts are neurotoxins that block the signals between nerves and muscles, including paradoxin, one of the most potent toxins of its kind known. It also contains powerful procoagulants that use up the body’s clotting factors so that blood stops clotting, and myotoxins that damage muscle. The comparison with other snakes is explained in is the inland taipan the most venomous snake? and in our list of the most venomous snakes.

A bite is a life-threatening medical emergency. Anyone bitten by any Australian snake should seek emergency medical help immediately (000 in Australia, 911 in the US, 112 in the EU or 999 in the UK). Taipan antivenom, first made in the 1950s from coastal taipan venom, is also effective against this species.

Behavior

Inland taipans are active by day, and mostly in the early morning. They bask briefly and forage in and around soil cracks and burrows, then retreat underground for the rest of the day. In cooler weather they may also come out in the afternoon. They spend most of their lives hidden, which is one reason so little was known about them for so long.

The species has a calm reputation. When disturbed, it usually tries to escape into the nearest crack. If it is cornered, it raises the front of its body in a tight, low S-shaped curve facing the threat and may then strike quickly and accurately. Read more in is the inland taipan aggressive?

Reproduction and lifespan

Males fight for females in late winter. In one observed bout, two large snakes twisted around each other for about half an hour, raising their heads and forebodies and lashing out with closed mouths. Mating has also been seen in late winter.

Inland taipans lay eggs. Females carry eggs in mid-spring, around November in the Southern Hemisphere, and lay them in old mammal burrows or deep crevices. Clutches usually hold about 10 to 20 eggs, averaging around 16. The eggs are about 6 by 3.5 cm (2.4 by 1.4 in) and hatch after about 9 to 11 weeks at 27 to 30 °C (81 to 86 °F). In poor years, when rats are scarce, females may skip breeding or lay fewer eggs.

How long inland taipans live in the wild is not known. In zoos they usually live about 10 to 15 years, and one snake at Australia Zoo is reported to have lived more than 20 years. Young snakes face the highest risk from predators.

Predators and threats

Adults have few natural enemies, but juveniles are vulnerable. The mulga snake (king brown snake), which resists the venom of many Australian snakes, has been recorded eating young inland taipans. The perentie, Australia’s largest lizard, shares much of the same country and readily eats venomous snakes once it is large enough.

Human threats are limited because the range is so remote and thinly settled. Possible pressures include overgrazing by livestock, which can change the floodplain vegetation, and introduced predators such as feral cats and red foxes, though their real impact on this species is poorly studied.

Conservation status

The IUCN Red List first assessed the inland taipan in 2017 and lists it as Least Concern. It is widespread within its range and not thought to be in overall decline, although the assessment notes that the effects of threats need more study and may matter locally. Like all native Australian snakes, it is protected by law. Queensland moved it from Near Threatened to Least Concern in 2014, while New South Wales and Victoria treat it as presumed or regionally extinct.

Discovery and history

The inland taipan has an unusual scientific history. Frederick McCoy described it in 1879 from the two Victorian specimens, naming it Diemenia microlepidota, the “small-scaled” snake, and William John Macleay described the Bourke snake as a separate species in 1882. After that the species was almost forgotten, and for about 90 years virtually nothing was added to what science knew of it.

In 1972 a grazier on a station west of Windorah in southwestern Queensland sent the head of an unfamiliar snake to the Queensland Museum. Herpetologists Jeanette Covacevich and Charles Tanner traveled to the site and found 13 live snakes, rediscovering the species. In 1981 studies of its anatomy and chromosomes showed that it belongs in the same genus as the coastal taipan, and it has been called Oxyuranus microlepidotus ever since. Local Aboriginal people around Goyder Lagoon know it as dandarabilla.

Myths and facts

Myth: the inland taipan is the world’s deadliest snake. It has the strongest venom in mouse tests, but bites are extremely rare and no death has been conclusively linked to it since antivenom became available. Vipers in South Asia and Africa, and in Australia the eastern brown snake, cause far more deaths because they live close to people. See is the black mamba the deadliest snake? for how venom and real risk differ.

Myth: “fierce snake” means it is aggressive. The nickname reflects the venom, not the behavior. The coastal taipan, which lives near towns and farms along the northern and eastern coasts, is generally considered more dangerous in practice.

Fact: one bite could kill many people. Based on its LD50 and average yield, a single bite is often estimated to hold enough venom to kill at least 100 adult humans. This is a calculation from laboratory data, not an observed number.