Red-bellied black snake Pseudechis porphyriacus

Warning: Venomous

The red-bellied black snake (Pseudechis porphyriacus) is a species of elapid snake native to eastern Australia. Though its venom is capable of causing significant morbidity, a bite from it is not generally fatal and is less venomous than other Australian elapid snakes. It is common in woodlands, forests and swamplands of eastern Australia. It is one of Australia's best-known snakes, as it is common in urban areas along the eastern coast of Australia. It has an average total length (including tail) of 1.5 to 2 metres (4 ft 11 in to 6 ft 7 in).

Taxonomy

The red-bellied black snake was described by George Shaw in Zoology of New Holland (1794), placing it in the genus Coluber. He wrote, "This beautiful snake, which appears to be unprovided with tubular teeth or fangs, and consequently not of a poisonous nature, is three, sometimes four, feet in nature." The species name is derived from the Ancient Greek porphyreus, which can mean "dark purple", red-purple" or "beauteous". It was the first Australian elapid snake described. The accompanying illustration was attributed to James Sowerby, but is regarded as being produced from drawings by John White. The syntype is presumed lost. French naturalist Bernard Germain de Lacépède described it under the name Trimeresurus leptocephalus in 1804. His countryman René Lesson described it as Acanthophis tortor in 1826.

The genus Pseudechis was created for it by Johann Georg Wagler in 1830, though several subsequent species have been added.

Snake expert Eric Worrell analyzed the skulls of the genus and found that of the red-bellied black snake to be the most divergent. Its position as an early offshoot from the rest of the genus has been confirmed genetically.

Raymond Hoser described two subspecies in 2003: Pseudechis porphyriacus eipperi the Atherton Tableland and surrounds in North-east Queensland, which he noted was smaller, rarely attaining 2 m (7 ft) and had a white or pale pink rather than red belly, and Pseudechis porphyriacus rentoni from southeastern South Australia, which has a variable-coloured (often orange or even blueish-tinged) belly. He added that both were disjunct from the main red-bellied black snake population, and as the distinguishing traits of P. porphyriacus rentoni were not consistent then location was the most reliable way of identifying it. These subspecies have not been recognized by other authors. Hoser has been criticized by Hinrich Kaiser and colleagues for identifying some taxa on location alone.

As well as red-bellied black snake, the species has been called common black snake, redbelly and RBBS.

Description

The red-bellied black snake is glossy black on the dorsal surface and red, crimson or pink in colour on the lower sides and belly. The snout is often a lighter brown colour. It is a relatively medium species of snake reaching up to 2 metres (6 ft 7 in) in total length (including tail), with an extreme example measuring 2.5 metres (8 ft 2 in), although an average sized specimen would be closer to 1.4 metres (4 ft 7 in). Like all Elapid snakes it is front fanged. It has 17 mid-body scale rows. Juveniles are similar to the eastern small-eyed snake, with which it can be easily confused.

The red-bellied black snake can have a strong smell, which some field experts have used to find the snakes in the wild.

Other similar species include the blue-bellied black snake (Pseudechis guttatus) and copperheads of the genus Austrelaps

Distribution and habitat

The red-bellied black snake is native to the east coast of Australia. It can be found in the urban forest, woodland, plains and bushland areas of the Blue Mountains, Canberra, Sydney, Brisbane, Melbourne, Cairns and Adelaide. The Macquarie Marshes marks a western border to their distribution in New South Wales. It is most commonly seen close to dams, streams, billabongs and other bodies of water, although they can venture up to 100 m away. In particular, the red-bellied black snake prefers areas of shallow water with tangles of water plants, logs or debris.

Behaviour

Red-bellied black snakes have multiple places they can hide in their habitat including logs, old mammal burrows, and grass tussocks. They can flee into water and hide there, with one report of one staying submerged for 23 minutes. When swimming they may have the whole head or the nostrils above the water's surface. Within their habitat, red-bellied black snakes appear to have ranges or territories that they are familiar with and generally remain within. A 1987 field study in three New South Wales localities found that they varied widely, from 0.02 to 40 hectares in size.

The red-bellied black snake is generally not an aggressive species. However, when provoked, it will recoil into its striking stance as a threat, but will try to escape at the first opportunity. It is generally active by day, though nighttime activity has occasionally been recorded. When not hunting or basking it may be found beneath timber, rocks and rubbish or down holes and burrows.

Snakes are active when their body temperatures are between 28 and 31 C. They also thermoregulate by basking in warm sunny spots in the cool early morning and rest in shade in the middle of hot days, and may reduce their activity in hot dry weather in late summer and autumn. In July 1949, six large red-bellied black snakes were found hibernating under a concrete slab in marshland in Woy Woy, New South Wales. Groups of up to 6 hibernating red-bellied black snakes have been recorded from under concrete slabs around Mount Druitt and Rooty Hill in western Sydney.

Diet

The diet of red-bellied black snake primarily consists of frogs, but it also preys on reptiles and small mammals. They also eat other snakes, including those of their own species. Fish are hunted in water. As red-bellied black snakes grow and mature, they continue to eat the same size prey but add larger animals as well. Although they prefer live food, red-bellied black snakes have been reported eating frogs squashed by cars.

They are susceptible to cane toad toxins. The introduction of Cane toads in Australia dates to 1935, when cane toads (Rhinella marina) were introduced in an attempt at biological control of native beetles which were damaging sugar cane fields (a non-native plant). The intervention failed, mostly because the toads are on the ground while the beetles feed on leaves at the top of the plant. One research study concluded that in less than 75 years the red-bellied black snake had evolved in toad-inhabited regions of Australia to have increased resistance to toad toxin and decreased preference for toads as prey.

Reproduction

In spring, male red-bellied black snakes often engage in ritualised combat for anywhere from 2 to 30 minutes, even attacking other males already mating with females. They wrestle vigorously but rarely bite, and engage in head-pushing contests, where each snake tries to push his opponents' head downward with his chin.

Red-bellied black snakes are ovoviviparous; that is, they give birth to live young in individual membranous sacs. The young, numbering between eight and forty, emerge from their sacs very shortly after birth, and have an average length of about 12.2 centimetres (4.8 in).

Venom

The red-bellied black snake accounted for 16% of identified snakebite victims in Australia between 2005 and 2015, with no deaths recorded. Its venom consists of neurotoxins, myotoxins, coagulants and also has haemolytic properties. Bites from red-bellied black snake are rarely life-threatening, but require immediate medical attention. Symptoms of systemic envenomation—including nausea, vomiting, headache, abdominal pain, diarrhoea or diaphoresis—were thought to be rare, but a 2010 review found they occurred in most bite victims. Most people also go on to develop an anticoagulant coagulopathy in a few hours. This is characterised by a raised aPTT, and subsides over 24 hours. It resolves quickly with antivenom. A few people go on to develop a myotoxicity and associated generalised muscle pain and occasionally weakness, which may last for up to 7 days. The red-bellied black snake is the most commonly reported species responsible for envenomed dogs in New South Wales. In 2006, a 12 year old golden retriever suffered rhabdomyolysis and acute renal failure secondary to a red-bellied black snake bite.

Tiger snake antivenom is used to treat bites. While black snake antivenom can be used, tiger snake antivenom can be used at a lower dose. The smaller dose is cheaper to produce, and is less likely to cause a reaction in the patient. Patients may suffer anosmia.

Captivity

Red-bellied black snakes adapt readily to captivity and live on a supply of mice.