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Safety around snakes

In Australia, more than 80 per cent of bites occur when people try to catch or kill snakes. The golden rule is not to corner or attack a snake. As identification is often difficult, people are advised not to handle a snake even if they believe it is non-venomous. When dealing with a snake bite the priority is to prevent the poisons from moving from the bite site into the general circulation.

  • Do not try to catch a snake, or kill it.
  • Do not apply a tourniquet or suck the wound.
  • Do not wash the wound. Traces of venom help medical authorities identify the snake.
  • The victim must keep calm and as still as possible.
  • Wrap the affected limb firmly with an elastic bandage or clothing, starting from the toes or fingers and moving towards the trunk.
  • Splint the limb to prevent movement. Do not remove the bandage. 
  • Call an ambulance or transport the victim to hospital.

Fang design

Many snakes, such as pythons, have lots of sharp teeth, but none dedicated to delivering venom. However, various groups have evolved pairs of hollow, elongated teeth which are connected to venom glands. As the snake bites, muscles in this gland contract and venom is squeezed through the teeth. Some snakes have fangs in the back of their mouths where leverage enables the snake to drive the tooth well into the victim — as long as it has been caught securely. Rear-fanged snakes include the brown tree snake, Macleay’s water snake and mangrove snakes. These are not considered dangerous to humans.

The more dangerous snakes, from an Australian point of view, are those with fangs at the front of their mouths. The fangs of almost all dangerous Australian snakes are fixed — they cannot move — so their length is determined by the need to fit in the mouth.

The longest fangs are found in the taipan, with the mulga, western brown, death adder and Collett’s black snake coming close. Vipers, found outside Australia, have the longest fangs, hinged to fold back into the mouth. Only one Australian species, the death adder, has fangs which fold back, but only to a limited extent.

Documents

Tropical Topics, No. 80, January 2004, Snakes in the savannas
Venomous snakes feature in this issue of Tropical Topics, with information on their toxicity, evolution, and reproduction. A brief description is given for a selection of venomous snakes found in Australian tropical savannas, and a list of useful references is provided. Also in this issue are brief notes on Kookaburras, Tuckeroo Cupaniopsis anacardioides, Water Rats, and kites that spread fires. [pdf 758.0 kb]

Snakes of the tropical savannas

From Tropical Topics newsletter, No. 80 January 2004, produced by Stella Martin at the Queensland Environmental Protection Agency. Download the PDF to read the whole issue.

Snake families | Evolution | Venom | Venomous but not necessarily deadly |

Snake families

Emerald python, Cape York
Emerald Python, Morelia viridia, Cape York
Photo: Greg Calvert 

There are six main snake families in Australia—elapids (venomous snakes, the largest group), colubrids ('harmless' snakes) pythons, blindsnakes, file snakes and sea snakes.

Australia is the only continent where venomous snakes (70 per cent) outnumber non-venomous ones. Despite this, very few deaths result from snake bites. It is estimated that between 50,000 and 60,000 people die of snake bite each year around the world. By comparison, in Australia there have been only 38 deaths from snake bites during the last 23 years — fewer than two a year.

Evolution

Snakes are generally believed to have evolved from lizards.

Why they lost their legs (though pythons retain traces of legsin the form of small spurs) has been disputed.

Originally this was thought to have happened to allow these creatures slidemore easily along narrow burrows. However, studies of thefeatures of early snakes suggest they were not burrowers butmay instead have developed from swimming, eel-like, marinegoannas called mosasaurs.

We know about Australia’s earliest snakes only from fossils. Many of these belonged to the Madtsoiidae group, some ofwhich are thought to have been enormous: 6–10m in length with the girth of a telegraph pole. Remains of these snakes have also been found in Africa and South America suggesting they evolved before the ancient continent of Gondwanabegan to break up about 180 million years ago.

Curiously, although they became extinct on all other continents about 55 million years ago, in Australia — where their remains areparticularly abundant, especially at the Riversleigh Australian Fossil Mammal Site in Boodjamulla National Park inQueensland — they started to decline only about 15 million years ago.

It is thought that some of these impressive animals were still around within the last 100,000 years so it is possible that Aboriginal people encountered them when they arrived. There may, in fact, be links to the Rainbow Serpent Dreamtime beliefs, widespread among Aboriginal people.

Venom 

Australia is home to some of the most venomous snakes in the world. Why?

It is possible that strong venom may have evolved chiefly as a self-defence strategy. It is interesting to look at the habits of different venomous snakes. Some, such as the coastal taipan (Oxyuranus scutellatus), bite their prey quickly, delivering a large amount of venom, and then let go. The strong venom means that the prey doesn’t get far before succumbing so the snake is able to follow at a safe distance. Taipans eat only mammals — which are able to bite back, viciously. This strategy therefore allows the snake to avoid injury.

On the other hand, the most venomous snake, the inland taipan (O. microlepidotus), also known as the small-scaled or fierce snake, tends to live in the burrows of its main prey, the long-haired rat. Unable to retreat from its prey in this confined space it has a greater need to finish it off quickly. Its more risky attack strategy entails holding its prey with its body and biting repeatedly. However, this snake can deliver, in one bite, more than40 000 times the venom needed to kill a 200 gram rat and it contains a special component which causes the toxin to rapidly invade the body. Its prey has little chance to fight back. While coastal and inland taipans eat only mammals, other venomous snakes feed largely on reptiles and frogs. Venom acts slowly on these ‘cold-blooded’ creatures with slow metabolic rates, so perhaps it needs to be especially strong. In addition, as many prey species develop a degree of immunity to snake venom, a form of evolutionary arms race may have been taking place.… but not necessarily deadly.

Venomous but not necessarily deadly  

Some Australian snakes may be particularly venomous, but they are not the most dangerous for humans, as the graph below shows. The low fatality rate, compared with many other parts of the world, is attributed to Australia’s sparse population, use of better footwear and better medical treatment, including availability of antivenoms. Also, Australian snake are shy and comparatively reluctant to bite, often not injecting venom when they do bite. Indeed, a New South Wales study showed that it is humans who are more aggressive with people 100 times more likely to attack a snake than the other way round.

snake graph4

A comparison of annual snakebite fatalities per million people from around the world. To standardise comparisons, published data compiled between 1945-1960 was used. Australia’s current figure is 0.13 per million but during the period used here it was 0.45 per million. Graph courtesy Brian Bush.