King Brown Snake
With its wide distribution the Mulga Snake overlaps with a number of other similar-looking elapids, particularly species of brown snake Pseudonaja spp., and other members of its own genus Pseudechis, e.g. the Spotted Mulga Snake Pseudechis butleri.
As debate continues over its taxonomic identity, there’s no doubting the Mulga Snake’s status as one of Australia’s most formidable snakes.
Number of species
A number of new species of mulga snake have been proposed, however at present only one species is universally recognised, Pseudechis australis. Recent molecular studies have lent support to the identification of a number of cryptic species within P. australis.
Juvenile snakes may be of average built but adults are usually quite robust, with a broad deep head and bulbous cheeks. The scales on the back, sides and tail are usually two-toned; a darker colour covers the distal portion of the scale to various degrees (from just the very tip to almost the entire scale) and may be brown, reddish brown, coppery brown or brownish black. The base of the scale is usually yellowish white to greenish yellow, contrasting with the darker colour to produce a reticulated effect. Individuals from the far northern arid areas have almost no darker pigment whereas southern populations are almost black. The tail is usually darker than the body and the top of the head is a uniform colour similar to the dark of the body scales. The eyes are relatively small with a pale reddish brown iris. The belly is cream to salmon-coloured, and often has scattered orange blotches.
Mid body scales in 17 rows, ventrals 185-225, anal scale divided, subcaudals single anteriorly and divided posteriorly (occasionally all single).
The largest specimen reliably measured was an individual from near Darwin that measured 3.3 m in total length. However they generally average around 200cm (total length). Among adult specimens in museum collections, mean snout-vent lengths are significantly larger in males than in females.
Mulga Snakes have the widest distribution of any snake species in Australia, ranging throughout the continent except for the extreme southern and general southeastern parts.
Also found in south-eastern Irian Jaya, and possibly western Papua New Guinea.
The species occurs in a wide variety of habitats, from closed tropical mosoon forest to Triodia hummock grassland, chenopod shrubland and almost bare gibber or sandy desert. Mulga Snakes may also occur in highly disturbed areas such as wheat fields. They shelter in disused animal burrows, in deep soil cracks, under fallen timber and large rocks, and in deep crevices and rock cavities in outcrops.
Southern specimens that are typically darker coloured have been observed basking in winter.
Feeding and Diet
In the wild, Mulga Snakes feed on a wide variety of vertebrate prey, including frogs, reptiles, reptile eggs, bird eggs, birds and mammals. The species also occasionally eats invertebrates and carrion.
Mulga Snakes are apparently immune to the venom of at least one of their snake prey, the Western Brown Snake Pseudonaja nuchalis, and show no ill-effects when bitten by their own species. Unfortunately the Mulga Snake is not immune to the toxic Cane Toad, which is thought to have led to the snake’s decline in some northern parts of its range.
Other behaviours and adaptations
The species may be active both during the day and night (according to temperature), with diminished activity during mid-day and between midnight to dawn. During the hottest months, particularly in the northern parts of their range, Mulga Snakes become most active in the late evening and early hours after dusk.
Life history modes
crepuscular, diurnal, nocturnal, terrestrial
Male combat has been recording in early-mid spring for this species. The males entwine their bodies and with their raised heads attempt to push over their opponent.
In southwestern Australia, mating has been recorded in early spring, and in Eyre Peninsula in mid-spring. In a survey of specimens in all the major Australian museums, females with yolking follicles had been collected between mid-winter and late spring, and females carrying oviducal eggs were from mid-summer, mid- autumn and early spring. In northern populations breeding may be aseasonal or associated with the wet and post-wet season. The time between the last courtship/mating and egg-laying varies from 39 to 42 days. Clutch sizes range from 4 to 19, with an average of around 9. There is a significant positive relationship between the snout-vent length of the female and clutch size.
The eggs may take between 70 and 100 days to hatch, depending on the incubation temperature. There has been a case where two hatchlings emerged from one egg - the egg was normal sized but the hatchlings were about half the size of their clutch mates.
Predators, Parasites and Diseases
Large Mulga Snakes have few enemies, however small specimens may fall victim to birds of prey.
The species' known endoparasites include nematodes. Older specimens often carry a high burden of ticks.
Not listed as threatened.
Danger to humans and first aid
The temperament of the Mulga Snake appears to vary with locality. In southern areas of Eyre Peninsula and west coast of South Australia it is a shy, quiet snake, however northern specimens are reported to be quite excitable when disturbed.
When threatened, the Mulga Snake inflates its body and holds its head and flattened neck in a wide curve parallel to the ground. It will throw its head and neck from side to side, hissing loudly as it does. If pressed further it will lash out wildly in an attempt to bite. Mulga Snakes bite savagely and may hang on and chew as they inject their venom. The venom is highly toxic and can be expressed in enormous quantities. Its effects are mainly haemolytic (breaks down blood cells), cytotoxic (disrupts cells), myotoxic (affects muscle), and also mildly neurotoxic (affects nerve cells). Anyone suspected of being bitten should seek immediate medical attention. Should antivenom be required it is important to note that despite the alternative common name of King Brown Snake, the Mulga Snake is in fact a member of the black snake genus Pseudechis, therefore Black Snake Antivenom will be necessary.
Cogger, H. (2000) “Reptiles and Amphibians of Australia”, Reed New Holland
Wilson, S. and Swan, G. (2008) “A Complete Guide to Reptiles 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