Eastern brown snake

Identification

The eastern brown snake is a medium-sized snake with a slender to moderate build and a smallish head that is barely wider than its neck¹. Adults can be almost any shade of brown, from light tan, chestnut or burnt orange to nearly black, and the back is usually plain¹. The belly is cream, yellow or orange with pinkish-orange, brown or grey blotches, and the smooth, slightly glossy scales lie in 17 rows at midbody¹. The eye has an orange iris ringed with black, a round pupil and an obvious brow ridge¹. Hatchlings have a dark patch on the head and nape, and some are banded along the whole body; these markings usually fade with age, although some populations keep the bands as adults¹.

Adults average about 1.5 m long, and the largest specimen reliably measured was 2.01 m¹.

Distribution

The eastern brown snake is widespread in eastern Australia, from northern Queensland to South Australia, with isolated populations in central and western parts of the Northern Territory¹. The Reptile Database records it from New South Wales, Victoria, Queensland, South Australia, the Northern Territory and Western Australia, and from Papua New Guinea². Brown snakes of this species group also live in southern and eastern New Guinea¹. These were once thought to have been brought there by people, but genetic evidence suggests they arrived naturally from northern Queensland and Arnhem Land during the Pleistocene¹.

Habitat

This snake lives in a wide range of habitats but avoids rainforest and alpine areas, preferring open country such as woodland, scrubland and savannah grassland¹. In the arid inland it is found along watercourses and swampy areas that flood at least seasonally¹. It can be especially common on farmland and is often met on the edges of towns and cities¹. When inactive it shelters under logs and rocks, in deep soil cracks and animal burrows, and readily uses sheets of iron and building materials¹.

Behaviour

The eastern brown snake is active mainly by day, although in very hot weather it may hunt in the late afternoon or early evening¹. It can be out on mild winter days and has been seen basking at air temperatures as low as 14 °C¹. It is alert and nervous: approached from a distance it usually flees or keeps still, but if surprised or cornered it puts on a threat display¹. In this display it spreads its neck sideways and may lift the front of its body into an S-shaped coil with the mouth slightly open, and this neck-spreading comes before most bites¹. Many bites have happened when people tried to kill the snake¹.

Diet

It eats a wide range of vertebrates, including frogs, reptiles and their eggs, birds and mammals, especially introduced rats and mice¹. Smaller snakes eat proportionally more lizards, while larger ones take more warm-blooded prey¹. It hunts actively, searching likely hiding places with its good eyesight, and subdues prey with both venom and constriction¹. Land clearing for farming brought plentiful rodents, and the species’ numbers have grown as a result¹.

Reproduction

The eastern brown snake lays eggs². Breeding begins in mid to late spring, when males wrestle in ritual combat for access to females¹. Females lay up to 25 eggs, 15 on average, and may lay several clutches in a good season¹. The eggs take from 36 days at 30 °C to 95 days at 25 °C to hatch, and communal nests have been found, including one in an abandoned rabbit warren¹. Eastern brown snakes have lived for 7 years in captivity and probably live for at least a decade¹.

Venom and medical significance

The World Health Organization places the eastern brown snake in its highest category of medical importance in Australia, and a specific brown snake antivenom has been made there since 1956^3,5. Its fangs are only about 3 mm long and a bite may be painless, yet it causes more snakebite deaths than any other Australian snake¹. Its venom contains powerful nerve toxins and clotting toxins, as well as toxins that affect the heart and kidneys, and deaths have occurred from bleeding into the brain¹. In a study of 136 people envenomed by brown snakes in Australia, all lost the ability to clot their blood normally, and over a third had serious complications such as collapse, kidney injury from damaged small blood vessels, major bleeding or cardiac arrest³. From 2005 to 2015, brown snakes caused 41% of confirmed envenomings and 17 of the 23 snakebite deaths recorded by the Australian Snakebite Project⁴. Anyone bitten should go to hospital immediately.

Conservation

The eastern brown snake is listed as Least Concern on the IUCN Red List, based on an assessment published in 2018⁶. It readily lives in areas disturbed by people and feeds on abundant introduced house mice, so the Australian Museum considers its future assured¹. Many are still killed on roads or by landowners, and snakes that eat cane toads die quickly from the toads’ poison¹. In New South Wales, all native reptiles are protected under the Biodiversity Conservation Act 2016⁹.

Similar species

The eastern brown snake is easily confused with other brown snakes (Pseudonaja), and close inspection is usually needed to tell them apart¹. It has a flesh-pink mouth, while the speckled, western and northern brown snakes have a mostly black mouth, and its blotched belly separates it from the peninsula brown snake, whose belly is entirely dark¹. The coastal taipan (Oxyuranus scutellatus) usually has a pale face and snout, a large head and a slender neck, whereas a brown snake’s snout is the same colour as its body or darker and its head is barely wider than its neck⁷. Banded eastern brown snakes can also be mistaken for tiger snakes (Notechis scutatus)⁸. These differences are not a safe basis for handling any snake. Keep your distance from every snake you cannot identify.

In captivity

The eastern brown snake is dangerously venomous and is not suitable as a pet. In New South Wales, keeping venomous native reptiles requires an advanced reptile keeper licence and references confirming experience in handling them¹⁰. Captive eastern brown snakes may eat each other, especially when crowded; one 165 cm snake swallowed a 150 cm cagemate¹.