Inland Taipan

Introduction

Often cited as the world’s most venomous snake, the Inland Taipan is far from the most dangerous. Unlike its congener, the common and fiery-tempered Coastal Taipan, this shy serpent is relatively placid and rarely encountered in its remote, semi-arid homeland.

Identification

A medium to large snake, with a robust build and a deep, rectangular-shaped head. Dorsal colour varies from pale fawn to yellowish-brown to dark brown, with the head and neck being several to many shades darker than the body. Colour changes seasonally, with individuals becoming darker in winter and fading in summer. Many dorsal scales have a blackish-brown lower anterior edge which creates a broken herringbone pattern along the length of the body. The ventral surface is yellowish with orange blotches; this colour often extends to the lowermost lateral scales. Eyes are large, with a very dark iris and round pupil.

Midbody scales in 23 rows, ventrals 211-250, anal scale single, subcaudals divided.

Habitat

Inland Taipans are associated with the deep cracking-clays and cracking-loams of the floodplains, however they also venture onto nearby gibber plains, dunes and rocky outcrops if cover is available. The vegetation in these areas is usually sparse, consisting of chenopod shrubs, lignum and the occasional eucalypt near the water channels.

The snakes shelter in soil cracks and crevices, and in holes and mammal burrows.

Distribution

The species occurs in the Channel country of south-western Queensland and north-eastern South Australia. There are two old records for localities further south-east, i.e., the junction of the Murray and Darling Rivers in northwestern Victoria (1879) and "Fort Bourke" (= Bourke?), New South Wales (1882); however the species has not been collected in either state since then.

Biomaps map of Inland Taipan specimens in the Australian Museum collection. http://www.biomaps.net.au/biomaps2/mapam.jsp?cqn=Parademansia%20microlepidota&cql=sn&csy=Square

Seasonality

Road-killed specimens have been found in "winter", hence the species is presumably active on the surface at this time of year.

The seasonal change in body colouration presumably helps the Inland Taipan to warm up quickly during the cooler months (dark colour) and avoid overheating in the warmer months (pale colour).

Feeding and diet

In the wild Inland Taipan appear to feed entirely on small to medium-sized mammals, particularly the Long-haired Rat Rattus villosisimus, as well as the introduced House Mouse Mus musculus and various small dasyurids. Prey is usually cornered in a burrow or soil crack before being bitten several times in quick succession. The venom acts so rapidly that the snake can afford to hold on to its prey instead of releasing (to avoid injury) and waiting for it to die.

In captivity Fierce Snakes may also accept day-old chicks in addition to rats and mice.

Other behaviours and adaptations

The species is primarily, if not exclusively, diurnal in its activity on the surface. They are most active in the early half of the morning, briefly basking and foraging in or near deep soil cracks and animal burrows, before retiring to shelter for the rest of the day. In cooler weather the snakes may also be found active in the afternoon.

The favoured prey of the Inland Taipan is the Long-haired Rat Rattus villosissimus. This species goes through “boom-and-bust” cycles, breeding up to plague proportions during the good seasons and virtually disappearing during times of drought. When rats are in high numbers the snakes grow very sleek and fat, however once the rats disappear the snakes must depend on less prevalent prey and/or draw upon their fat reserves until the rats return.

Breeding behaviours

Behaviour typical of male combat has been recorded occurring in late winter between two large, but unsexed, individuals. During the approximately half-hour combat, the snakes intertwined, raised their heads and forebodies and "lashed out" at each other with closed mouths. Inland Taipan have also been observed presumably mating in the wild in late winter. Females with oviducal eggs can be found in mid-spring (second half of November). Clutch size ranges from 11-20, with 16 being the average. The eggs measure 6 x 3.5cm when laid and take 9-11 weeks to hatch at 27-30°C. Newly-hatched young have a total length of around 47cm long.

In captivity, females can produce two clutches within what would effectively be one breeding season.

Conservation status

• Rare (Queensland)
• Presumed extinct (NSW, Victoria)

Danger to humans

Inland Taipans are rarely encountered in the wild by the average person because of their remoteness and brief above-ground appearance during the day. Compared with the related Coastal Taipan (and despite the alternative name ‘Fierce Snake’) this species is actually quite shy and many reptile keepers regard it as a placid snake to handle. However, like any animal, it will defend itself when provoked. Firstly it makes a threat display by raising its forebody in a tight low S-shaped curve with its head facing the offender. Should the offender choose to ignore the warning the Inland Taipan will strike, making a single bite or several quick bites. Symptoms of envenomation include headache, nausea, vomiting, abdominal pain, collapse and paralysis. The venom of the Inland Taipan is extremely potent and is rated as the most toxic of all snake venoms in LD50 tests on mice. As well as being strongly neurotoxic the venom contains a ‘spreading factor’ (hyaluronidase enzyme) that increases the rate of absorption. The venom’s toxicity coupled with its spreading action makes a bite from a Fierce Snake potentially life-threatening, and anyone suspected of receiving a bite should seek immediate medical attention.

To date only a handful of people have ever been bitten by this species, and all have survived due to the quick application of correct first aid and hospital treatment.

References

Cogger, H. (2000) “Reptiles and Amphibians of Australia”, Reed New Holland

Greer, A.E. (2006) “Encyclopedia of Australian Reptiles : Elapidae”, Australian Museum

Ehmann, H. (1992) “Encyclopedia of Australian Animals : Reptiles”, Australian Museum, Angus & Robertson

Mirtshin, P. and Davis, R. (1991) “Dangerous Snakes of Australia”, revised edition, Ure Smith Press

Wilson, S. and Swan, G. (2008) “A Complete Guide to Reptiles of Australia”, Reed New Holland