Weekly Wildlife Profile: Red Belly Black Snake

Red-bellied Black Snake . (Photo credit: Wikipedia)

The Red-bellied Black Snake (Pseudechis porphyriacus) (RBBS) is one of natures true gentleman who suffers from far too much bad press. In this animal profile, we explore the myths and facts surrounding this iconic Australian native species of venomous snake.

Morphology

The RBBS is one of Australia’s most iconic species. Its dorsal surface is black and often highly glossy while its belly is usually pink ranging to crimson red at the sides.  A bright red line is often visible along the sides of the animal when the snake moves. The danger with using such descriptions to visually identify a snake is the risk of misidentification. RBBS are similar in appearance to another (more venomous) snake known as the Eastern Small Eyed Snake (pictured below for comparison). The only real method of identifying a snake is to count its scales and study the scale configuration. This technique should only be preformed by a specialist. For matter of interest, however, the RBBS has 17 scales per mid body row.

This small eyed snake could easily be misidentified as a Red Bellied Black Snake due to its similar appearance. (Photo credit: Snake Catchers Brisbane)

The RBBS is a medium size snake, ranging to 2 metres in length although larger individuals have been recorded. Males are generally larger than females. Maturity is usually reached within two to three years. The lifespan of a wild RBBS is unknown, although they have been known to live to 20 years in captivity. It is assumed that wild animals may live longer given their slower growth patterns.

They are mostly active during the day but take refuge in burrows, under logs or any other shade source to avoid excessive heat. They are known to occur throughout the eastern seaboard, inhabiting grasslands, woodlands, forests and urban areas alike. As a semi aquatic snake, they are often found close to water ways. Their diet mostly consists of frogs, however, like most Australian snakes, they also feed on other reptiles, including smaller members of their own species. 

Red-bellied Black Snake (Photo credit: teejaybee)

The Red Bellied Black Snake is known to be a shy, non aggressive snake. When provoked, they will strike at their attacker and then attempt to escape while the attacker is distracted. The RBBS is an elapid, meaning its fangs are fixed in the front of the mouth. The venom of this species is a cocktail of neurotoxins, myotoxins and coagulants. Their bite often causes necrosis and while bites should be considered serious and medical attention should be obtained immediately, they are rarely considered life threatening. Although tiger snake anti-venom is often used to treat patients with confirmed RBBS bites, they are unrelated to tiger snakes. The use of tiger snake anti-venom is directly related to the costs associated with anti-venom production, rather that any other correlation.

It is important to note that snake bites of any species should be considered dangerous. When snake bite is suspected, sit the patient down, wrap the limb with a pressure bandage and wait for medical attention to arrive. The bandage should be applied similarly to that of a sprained ankle and NOT as a tourniquet. Do not move the patient. There is no need to attempt to capture or kill the snake. Do not attempt to cut out, wash, suck out the venom or otherwise tamper with the bite site. The minute traces of venom that is swabbed by medical staff from the bite site is used to confirm the venom type that will allow medical attention.

Conservation Status

The RBBS is not currently considered threatened, and does not appear on any state conservation lists. This is primarily because populations when viewed at a state level appear to be stable. Notwithstanding, several threatening processes are identified and should be noted.

As part of their life cycle, RBBS are reliant on water sources. When urbanisation occurs, water sources are often adversely affected by pollution. This reduces localised frog populations which in turn contributes to a decrease in RBBS numbers. Land use competition is another significant factor as habitat destruction results in restricted areas of safe habitat for RBBS.

Red Bellied Black Snake (Photo credit: Aaron Gustafson)

The introduction of the cane toad has been identified as a contributing factor in the declining populations of many reptile species. The RBBS has been identified as one of the more signification impacted species due to their dietary dependency on frogs. Reptiles are unable to identify the potential dangers of consuming cane toads as opposed to other frogs and are often unable to avoid exposure to a lethal dose of toxin.

Although legislation is slow to identify these threats accordingly, there is significant support in the scientific community to apply conservation legislation to this species. In 2009, Minister for the Environment, Heritage and the Arts decided to approve the development of a threat abatement plan to deal with the cane toad intrusion. Ironically, cane toads were identified to have a negative impact on native reptile species during the approval process, and RBBS in particular were named as one species suffering notably from cane toads.

REPRODUCTION

Red Bellied Black Snakes are ovoviviparous meaning they give birth to live young which are born in individual membranous sacs. The female will give birth to up to 40 neonatal hatchlings. Approximately 20cm at birth, these hatchlings are independent at birth, and despite popular urban mythology, are as venomous as their parents at birth. Mortality rates amongst hatchlings is known to be high, and few make it to adulthood.

Ritualised combat between males can be seen throughout spring when males seek out females to mate with. During combat that may last for several hours, males raise up and attempt to push each other down using nothing but muscle strength. Once a victor has been determined, the lose will leave the territory in search of a weaker competitor.

 

Mythology

It is commonly believed that RBBS will chase and eat other snake species, including the worlds second most deadly snake, the Eastern Brown Snake. This urban legend is actually true. RBBS like many species of snake are cannibalistic, but unlike other species, they do not tolerate direct competition and will actively eat perceived threats.

Of recent times it has been suggested that the RBBS is adapting to the risks of cane toads. According renown herpetologist Rick Shine, RBBS are showing some remarkable evolutionary traits to cope with this ongoing threat. It seems that RBBS are developing smaller heads which make it difficult to ingest a toad that may deliver a lethal dose of toxin. Additionally to this physical adaptation, it seems that RBBS are learning to avoid eating toads, possibly making this knowledge a hard-wired instinct. This evolutionary adaptation has been exceedingly rapid; it has only been 70 years since the cane toads introduction.

Pseudechis porphyriacus (roadkill), found between Marlo and Cape Conran, Victoria, Australia; tooth exposed (Photo credit: Wikipedia)

It is often believed that RBBS are a threat to humans. As pointed out above, their venom is not considered to be dangerous. Despite common urban mythology, no one has ever died of a bite from this species in Australia. Notwithstanding, seek medical attention if a bite is suspected.

It is not unusual to hear snakes being referred to as aggressive. This label is often undeserved. Snakes react to threats by striking out as a warning, much like a dog will bark at a perceived threat. Although most bites do not deliver venom (most strikes are actually close-mouthed lunges!) it is unfortunate that the potential risk of a lethal bite can not be ignored. This risk often causes hysterical reactions in people. It should be noted, however, that the snake is often reacting in a defensive manner, waiting for an opportunity to escape its predicament.

Snakes are territorial by nature. In an established home range, snakes will know the location of food, water and shelter sources. They often will spend their entire lives within this home range.

I have heard many stories of snakes chasing their intended human victims. When the facts are observed, the people are often running in the same direction as the snake who is desperately trying to avoid them.  

It is fact that snakes can not hear. They lack open ear structures, although, some species do in fact have the evolutionary remains of ear drums within the skull. Snakes use their belly scales to detect minute vibrations through the ground beneath them that foretells of approaching danger (in the form of heavy footed animals).

Snakes have poor eyesight. Most snakes have a limited field of vision with most seeing less than six feet. Unless an object is moving, it is often not seen. As a result, snakes tend to react poorly to sudden unpredicted movement. I have seen snakes striking at shadows that suddenly move out of confusion (ie: something large suddenly moving right beside them such as an ambush predator that poses a threat). If you do find yourself in close proximity to a snake, stand still.

Snakes, including the RBBS are useful bio control agents for pest species such as mice and rats. While their diet is primarily amphibian and reptile base, they will never say no to an easy meal such as a nest of mice and rats.  Like all snakes, they are also prone to being opportunistic, such as this snake feasting on eggs.

Pseudechis porphyriacus eating eggs of the green tree snake (Photo credit: Wikipedia)

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References

ABC report on Red Bellied Black Snakes featuring Dr Rick Shine: http://www.abc.net.au/local/audio/2009/06/24/2607346.htm

Cogger, H. (2000). Reptiles and Amphibians of Australia (6th ed.). Sydney, NSW: Ralph Curtis Books.

Eastern Small Eyed Snake: Brisbane Snake Catchers

Shine, R. (1998). Australian Snakes: A Natural History (Revised ed.). Sydney, Australia: Reed New Holland.

Somaweera, R., Crossland, M., & Shine, R. (2011). Assessing the potential impact of invasive cane toads on a commercial freshwater fishery in tropical Australia. Wildlife Research, 38(5), 380-385. doi: http://dx.doi.org/10.1071/WR11026

Swan, G., Shea, G., & Sadlier, R. (2004). A Field Guide to Reptiles of New South Wales (Second ed.). Sydney, New South Wales: Reed New Holland.

Zukerman, W. (2010). Cane toad invasion: ugly, but not so bad. [Article]. New Scientist, 207(2777), 18-18.

I had opptounity to visit a collegue last week who had a Red Bellied Black Snake in care. This snake had been attacked by a dog. Here, wildlife carer Michael McGrath gives it the antibiotics vital for its recovery. (Photo Credit: Rhianna Blackthorn)

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