Red-bellied black snake

Identification

The red-bellied black snake is a medium-sized snake with a moderate to robust build and a head barely distinct from its neck¹. Its head and back are a uniform glossy black, except for the snout, which is often pale brown¹. The lowest scale rows on the sides and the outer edges of the belly scales are bright crimson, fading to duller red, orange or pink in the middle of the belly; in the north of its range the belly may be greyish-pink to white¹. Its body scales are smooth and glossy, and its eye has a dark iris, a round pupil and an obvious brow ridge¹.

Adults are usually 1.5–2 m long, and males grow slightly larger than females¹. The longest reliably reported total length is about 2.5 m (2,540 mm)¹.

Distribution

The red-bellied black snake is found only in eastern Australia^1,2. It occurs in scattered populations in northern and central eastern Queensland, and then more continuously from south-eastern Queensland through eastern New South Wales and Victoria¹. A separate population lives at the southern end of the Mount Lofty Ranges in South Australia¹. Despite claims to the contrary, it does not occur on Kangaroo Island¹.

Habitat

This snake is usually found in moist places, especially along streams and around swamps and lagoons, within forests, woodlands and grasslands, although it may also turn up well away from water¹. It lives in disturbed areas and on rural properties too, and is often seen around drainage channels and farm dams¹. It shelters in thick clumps of grass, logs, mammal burrows and under large rocks, and each snake seems to keep several favourite shelter sites within its home range¹. In south-east Queensland it is most often met in wetter vegetation, and is often found basking in sunny patches of grass⁹.

Behaviour

The red-bellied black snake is mainly active by day, but it can stay active well into the evening when the weather is warm¹. Active snakes keep their body temperature at about 28–31 °C by moving between sun and shade¹. It is a shy snake: when approached it often freezes, and if a person comes too close it usually flees towards the nearest shelter, which can look like an attack if that shelter is behind the person¹. If it cannot escape, it raises its forebody, spreads its neck, hisses loudly and may make mock strikes with its mouth closed¹. To escape a predator it may slip into water, and it has been recorded staying fully submerged for as long as 23 minutes¹. In spring, males travel up to 1,220 m in a day looking for females, and rival males wrestle each other when they meet¹.

Diet

It eats a wide range of animals with backbones, including fish, tadpoles, frogs, lizards, other snakes (even its own species) and mammals¹. In Queensland its main prey is frogs⁹. It hunts widely on land and in water and can climb several metres; in water it may forage with only its head under the surface or dive completely, and it has been seen stirring up mud, probably to flush out hidden prey¹. The introduced cane toad is deadly to it, and a snake can die quickly after eating or even mouthing one¹.

Reproduction

The red-bellied black snake gives birth to live young, and it is the only member of its genus to do so; the other black snakes all lay eggs¹. Mating takes place mainly in spring, from early October to November¹. Four to five months later the female gives birth to 5–18 young, each born inside a thin membrane and measuring about 28 cm¹. In some areas, pregnant females gather in small groups of up to six, basking together and sharing a night-time shelter¹. The young reach maturity in two to three years¹.

Venom and medical significance

This is a venomous snake of medical importance: the World Health Organization lists Australia’s black snakes (Pseudechis species) in Category 2, which covers highly venomous snakes that can cause disability or death⁵. Its venom mainly affects blood clotting and muscles, and symptoms include bleeding, pain or swelling at the bite, nausea, vomiting, headache, abdominal pain, sweating, muscle pain and weakness, and red-brown urine^1,3. In a study of 81 confirmed bites, 70% of patients developed effects through the body; among them, 61% had a clotting abnormality and 12% had muscle damage, and one patient needed help with breathing³. It caused 16% of the snake envenomings in Australia in 2005–2015 where the snake was identified, behind only brown and tiger snakes, yet neither study recorded a death and very few deaths have ever been attributed to it^1,3,4. Tiger snake antivenom is recommended for its bites, and black snake antivenom can also be used³. Anyone bitten should go to hospital immediately.

Conservation

The red-bellied black snake is listed as Least Concern on the IUCN Red List (assessment published in 2018)⁶. It is still fairly common in some areas, but its close link with wetlands makes it vulnerable when these are drained or badly managed¹. Cane toads are thought to have hit its numbers hard in the north of its range, including around Brisbane, although there are signs of recovery in some areas^1,9. Where toads have been present for decades, black snakes have evolved greater resistance to toad toxin and less interest in eating toads, in fewer than 23 snake generations since toads arrived in 1935⁷. In Queensland, all wildlife is protected under the Nature Conservation Act 1992⁸.

Similar species

The venomous eastern small-eyed snake (Cryptophis nigrescens) is smaller, reaching at most about 1.2 m, and has steely-black skin with pink belly scales; its pink colour does not extend up onto the sides, and its eyes are tiny^8,9. The Australian Museum also lists the blue-bellied black snake (Pseudechis guttatus) and copperheads (Austrelaps) as possible confusions¹. The harmless common tree snake (Dendrelaphis punctulatus) can be almost black and is sometimes killed when mistaken for a venomous black snake; it is far more slender, with a whip-like tail, large eyes and usually a lemon-yellow belly⁸. These differences are not a safe basis for handling any snake. Keep your distance from every snake you cannot identify.

In captivity

The red-bellied black snake is a venomous snake and is not suitable as a pet. Captive snakes readily eat rats and mice and are described as voracious feeders¹. Keeping them carries real risk: in one hospital study, 10 of the 57 people with systemic envenoming were snake handlers³. In Queensland it is an offence to take a snake from the wild, and keeping any snake requires a wildlife licence⁸.