Kangaroos are Australia's best-known animals. Since they were first seen by European settlers - who were amazed at such strange animals - a lot has happened to these unique creatures. There are now more of some kangaroo species, generally the larger ones, than when the European settlers arrived. Other species are gone forever, made extinct by surroundings that were changed too much for them to survive. Many of the surviving species are also decreasing in number. They, too, may become extinct if we do not take the necessary actions.
The Kangaroo Family
The rare Long-footed Potoroo lives only in Australia's south-eastern forests. Photo: F. Mercay A.N.T. Photo Library
Kangaroos, and their close relatives, vary greatly in size, ranging in weight from 500 grams to 90 kilograms. There are at least 69 different types of kangaroo, called species. These species are found naturally in the wild only in Australia and New Guinea, although feral populations of some species have been introduced in New Zealand, Great Britain and Hawaii. Recently, scientists have separated these species into two families (the Macropodidae and the Potoroidae) which together form a super-family known as the Macropodoidea (or macropods). The family Macropodidae includes kangaroos, wallabies, wallaroos, pademelons, tree-kangaroos and the forest wallabies of New Guinea. The family Potoroidae is made up of potoroos, rat-kangaroos and bettongs which are only found in Australia.
The best-known macropods are kangaroos, which is why the word 'kangaroo' is often used to describe any of the members of this family. We use "kangaroos' in this brochure whenever these animals are being discussed in general.
Getting Around
Kangaroos of all sizes have one thing in common - powerful back legs with long feet. They are distinguished from other animals by the way they hop on these strong back legs. Only a few other small mammals, such as hopping mice, do this.
Hopping uses slightly less energy than four-footed running, but this advantage is lost at low speed. To move slowly, kangaroos balance on their front paws and tail, and then swing their hind legs forward in a pendulum motion.
One of the many odd things about kangaroos is that, on land, they can only move their hind feet together but when swimming they can kick each leg independently. Tree-kangaroos can move each hind leg separately when climbing. It is also interesting to note that, while several species of kangaroos have tails that can wrap around and carry nesting material such as grass and small branches, not one of the tree-kangaroos has the ability to grasp branches with its tail.
Development of the Young in the Pouch
Kangaroos have adapted to the varied conditions across Australia in many ways. One of the most unusual, is the way females of some species can delay the progress of pregnancy. In this way the female is ready to give birth to a replacement for her pouch young if it dies early, or within a week when it permanently leaves the pouch. This ability to delay births means that there can be up to 12 months between a mating and the birth of the young one resulting from that mating (when the normal gestation period is less than 35 days). It also means that the species can best respond to periods of drought and plenty.
Species which have this unusual ability normally mate again soon after the female gives birth. The tiny newly born kangaroo (less than 25 mm long) moves unaided into its mother's pouch and attaches itself to one of four teats. During the early stages of pouch life the young is permanently attached to the teat, but as it matures and begins to grow hair it also develops the ability to release and reattach itself to the teat.
In the late stages of pouch life, once it has a thin covering of fur, the young one begins to explore the outside world for increasing lengths of time until eventually it is old enough to be excluded permanently from the pouch. Complete weaning may take a number of months more after the young has permanently left the pouch. If the mother gives birth during this time, the newborn young will attach itself to a different teat to that being used by the older young. It is remarkable that when this happens the mother produces two different kinds of milk for the two different-aged young.
Different Species for Different Habitats
Australia is a large country with a wide range of landscapes and climates. Yet kangaroos, rock-wallabies, pademelons, rat-kangaroos, potoroos and others have found all sorts of living areas, or habitats, to suit them across the continent.
The Family Macropodidae
There is no real difference between the kangaroos and wallabies that form this family - other than size. Wallabies are generally smaller species, with none weighing over 25 kilograms. Wallaroos (or euros) prefer a habitat of steep, hilly country. On the other hand, the larger kangaroos prefer open flat plains, woodland or open forest.
Members of this family are generally grass and leaf eaters, able to convert dry grass into energy-giving glucose. Their ability to thrive on such a poor diet explains their success at living in so many parts of Australia.
The Red Kangaroo
The Red Kangaroo (Macropus rufus), is the largest living marsupial. Males can be as tall as two metres and weigh up to 90 kilograms. The animal can live in most of dry inland Australia, including desert, grassland, mallee and mulga country. It is able to go without drinking as long as green grass is available, and it adapts well to drought. Despite its name, the Red Kangaroo is sometimes a blue - grey colour, particularly the female. Together with the Eastern and Western Grey Kangaroos (Macropus giganteus and Macropus fuliginosus), these are the largest and best known of the kangaroos.
The Eastern and Western Grey Kangaroos
The Eastern and Western Grey Kangaroos live where rainfall is greater than 250 millimetres a year, through eastern Australia and across the southern coast to south-west Western Australia. Populations vary considerably according to conditions, but the two species are very common, except in Tasmania where small numbers of the Eastern Grey Kangaroo are found.
Wallaroos
There are three species of wallaroos. The common Wallaroo (Macropus robustus) is found throughout mainland Australia and has a preference for rocky hills and stony rises where caves and rock ledges provide shelter from extremes of temperature. The Black Wallaroo (Macropus bernardus) in contrast is restricted to a small area of central and western Arnhem Land in the Northern Territory. The Antilopine Wallaroo, (Macropus antilopinus) is found in the tropical monsoonal forests of Northern Australia where it replaces the Red and Grey Kangaroos.
Tree-kangaroos
Tree-kangaroos are adapted to living in trees. They have stronger front limbs than other kangaroos, shorter hind legs, and feet with a rough-textured sole to allow for a better grip. Despite these features, they are awkward in trees. Most species are found in the dense forests of New Guinea. The two Australian species - Lumholtz's Tree-kangaroo (Dendrolagus lumholtzi) and Bennett's Tree-kangaroo (Dendrolagus bennettianus) - are found in small areas in the tropical rainforests of north Queensland. They feed on leaves and fruit.
Hare-Wallabies
Hare-wallabies look a bit like European Hares. They also have the European Hare's habit of hiding in tufts of grass. There are five known species of hare-wallabies. Of these, the Eastern Hare-wallaby (Lagorchestes leporides) is already extinct, and the Central Hare-wallaby (Lagorchestes asomatus) possibly so. Only one species, the Spectacled Hare-wallaby (Lagorchestes conspicillatus) is still widespread. Hare-wallabies mostly prefer tropical plains and grassland.
Nail-tail wallabies
These wallabies are so named because of the horny spur they have at the end of their tails. There are three species of nail-tail wallabies. One, the Crescent Nail-tail Wallaby (Onychogalea lunata) is extinct. The Bridled Nail-tail Wallaby (Onychogalea fraenata) is found only in a small area around Dingo in Queensland. The Northern Nailtail (Onychogalea urguifera) is found across the top end of Australia and is still common.
Rock wallabies
Rock wallabies are a large group of quite different-looking species. As their name implies, they prefer rocky regions. They are found throughout Australia. Because they prefer rocky gorges, cliffs and boulder jumbles, populations may be confined to widely separated and small areas. The most beautiful and strikingly coloured of all macropods is the Yellow-footed Rock Wallaby (Petrogale xanthopus).
Competition with feral goats is a problem for rock wallabies in many areas, and we believe foxes have reduced the numbers of some rock wallaby species. The Nabarlek (Petrogale concinna) is the smallest of the rock wallabies. It is unique among all marsupials in that it can continue to produce more than the normal four molar teeth. It prefers grasses rich in silica, and this abrasive food may explain why the animal can continually replace its grinding teeth.
Pademelons
The Red-necked Pademelon (Thylogale thetis) lives in sub-tropical rainforests and wet eucalypt forests. Photo: F. Park A.N.T. Photo Library
Pademelons are small wallabies that live in wet forest areas. There are three species in Australia: the Red-legged, Red-necked and the Tasmanian Pademelon (Thylogale stigmatica, T. thetis and T. billardierii). All live in rainforests or wet forests along the east coast and in Tasmania. The Tasmanian Pademelon is noted for its fine fur. It was once hunted in great numbers, but remains abundant today. Pademelons prefer similar habitats to potoroos, but have a different diet - they eat juicy grasses and shrubs. All three species remain common.
The Family Potoroidae
Potoroids are smaller macropods and were once called the rat-kangaroos. Some, such as the Musky Rat-kangaroo (Hypsipymnodon moschatus) of north Queensland rainforests are no bigger than a rat, and others grow to the size of a rabbit. Potoroids have an unusual diet - of mushrooms, roots, and insects. Mostly, they live in dense undergrowth and make nests from material carried by curling their tails around it. However, this is not always the case. Even though it has not been seen since 1935, the Desert Rat-kangaroo (Caloprymnus campestris) lived in one of the hottest, driest and most exposed areas in Central Australia.
Many of these small species have been badly affected by European settlement. Their preferred habitat has often been cleared for farming, and they have had to deal with the effects of many introduced animals, such as the fox, the cat and the rabbit. Two species of potoroids (there are nine known in all) are already extinct. Two more now survive only on coastal islands and another is rare.
Potoroos
Potoroos are mainly found in the wet forests and heathlands of east and south-east Australia. They feed in the open, but retreat to thick undergrowth for protection. The rare Long-footed Potoroo (Potorous longipes), is found only in the forests of east Gippsland and south-eastern New South Wales. The broad-faced pottoroo (Potorous platyops) was found in south-western Australia, but has not been recorded since 1875. Interestingly, Gilbert's Potoroo, the western Australian race of the Long-nosed Potoroo (Potorous tridactylus) was recently rediscovered in south-west Western Australia after an absence of more than 80 years.
Bettongs
Bettongs are found in drier areas than those preferred by the potoroos. Like most small macropods found in arid areas, bettongs are active at night to avoid moisture loss during the heat of the day. The Burrowing Bettong (Bettongia lesueur), does not drink. It gets the moisture it needs during the night from juicy sandhill plants.
One of the endangered species of bettongs, the Brush-tailed Bettong (Bettongia penicillata), has been bred and released on islands off the coast of South Australia in a program supported by the Australian Government. Only two species, the Tasmanian Bettong (Bettongia gaimardi) and the Rufous Bettong (Aepyprymnus rufescens), can be regarded as common. Even so, they are found over a smaller area than before, due mainly to clearing of their habitat for farms.
The Tasmanian Bettong (Bettongia gaimardi) Photo: D. Watts A.N.T. Photo Library
Conserving the Kangaroo
Of the 53 species of macropods found in Australia, six have become extinct since European settlement. For another 11 species, the area in which they are found has declined to less than half of what it was in that same 200 years.
What is being done?
Research and re-establishment programs
A lot of valuable research has been carried out into the habitat needs of declining species. But there is still much more to do. The Australian Government has assisted research and re-establishment programs for species such as the Bridled Nail-tail Wallaby, the Brush-tailed Bettong and the Rufous Hare-wallaby (Lagorchestes hirsutus).
Management, Protection and Commercial Harvesting
Management methods, such as deliberate control of fire patterns, have been tried on a small scale for particular species. All species of macropod are protected from hunting by state and territory legislation, except for a small number of large species for which commercial harvesting is permitted under approved management programs. The greatest threat to all macropods, however, is reduction or complete destruction of the habitats upon which they depend. This is particularly important for the smaller species where legislation to protect vegetation, such as the Vegetation Retention Scheme in South Australia, is more likely to help ensure their continued survival.
National parks and nature reserves have been important in helping to protect and re-establish some species, especially those that include the offshore islands of Western Australia. These islands are now the main, or only sites, of several species of macropods. But it is not always enough just to declare a reserve. Active management, including deliberate habitat changes, may be needed for some species.
Farmers and graziers have an important role to play in preserving macropods and other Australian wildlife. The Wallaby Creek area in north-eastern New South Wales has an unusually large number of different macropods - eleven species. There are no conservation reserves in the area, and it is used for light cattle grazing and timber production. Understanding why so many macropod species can live in this area, which is also being used for primary production, could help conservation in other areas outside of the reserve system.
About 75 per cent of Australian animal species are found only in Australia. Our kangaroos, wallabies, potoroos, pademelons, rat-kangaroos and the others are an essential part of our unique heritage. They can only be preserved by protecting the whole range of habitats found in Australia.
Threats to Survival
European settlement of Australia has worked against the survival of many native animals, including some species of kangaroo, in four main ways: fire patterns have changed, domestic stock have grazed large areas of native habitat, new predators have been introduced, and land has been cleared. Each of these factors has had a major, though different, effect on the habitat of our native species.
For example, the various hare-wallabies have:
lost much of their food and shelter because burning patterns have changed, with grasslands being transformed into grazing lands for sheep or cattle, or turned into farmland;
had to compete more and more with introduced species, such as sheep, cattle and rabbits, for the remaining food;
had to deal with massive wildfires, fuelled by a build up of forest debris, and with introduced predators, such as the fox and the cat.
Australia's arid environment is most fragile and here the impact of Europeans has been most drastic. Past distributions show that the arid areas favoured either large or small macropods - not the midsize species. Then, with the arrival of the fox and cat, the advantage of being small also vanished.
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Spider:
Australian Spider and Insect Bites
Of all the thousands of Australian spiders, arthropods and insects, only three have bites which alone are capable of causing death - the funnel-web spider (and related atrax species), the red back spider and the paralysis tick.
In most other spider or insect bites, rest and elevation, local application of ice packs and lotions, simple analgesics and antihistamines are all that is required.
In some patients, anaphylactic reactions may occur after insect bites, and these may be life threatening.
I have some information on the following:
Spiders:
Funnel Web
Red Back
White tail
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Spider Bites
The Sydney funnel web (and a few related atrax species) is unquestionably the most dangerous spider in Australia; the red back and the paralysis tick are the only other two arachnids with potentially fatal bites.
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Sydney Funnel Web (Atrax robustus)
Female funnelweb on the left, male on the right.
This is one mother of a spider!
It is a large (6-7 cm), black, aggressive, ugly looking spider with massive fangs. These are large and powerful enough to easily penetrate a fingernail. When disturbed it tends to rear up on its hind legs, aggressively exposing the fangs. The spider firmly grips its victim and bites repeatedly; in most cases the experience is horrific. The venom is highly toxic. Before an effective antivenom was developed, significant bites usually resulted in severe symptoms and death was not uncommon.
The Sydney funnel web spider is mostly found near Sydney (from Newastle to Nowra and as far west as lithgow but sightings have been reported as far north as Brisbane. Related species are found along the eastern coast of New South Wales. The Australian Museum has some some general info on their web site.
The venom of the slightly smaller male spider is five times as toxic as the female. This is unfortunate, as male funnel webs tend to roam about, particularly after heavy rain in summer, and often wind up indoors. The primary toxic component is atraxotoxin, which alone can cause all the symptoms. The venom also contains hyaluronidase and other components (GABA, spermine, indole acetic acid). For some strange reason, human beings (and other primates and monkeys) are particularly sensitive to the venom, whereas toads, cats and rabbits are almost unaffected!
Atraxotoxin causes acute massive release of neurotransmitters at autonomic and neuromuscular junctions with associated uncontrolled autonomic hyper-reactivity and muscle twitching, followed about 2 hours later by neurotransmitter depletion and weakness.
Symptoms
The bite is usually immediately painful, and if substantial envenomation occurs, symptoms commence usually within a few minutes. They include, progressively:
Piloerection, sweating, muscle twitching (facial and intercostal, initially), salivation, lacrimation, tachycardia, and then (fairly rapidly) severe hypertension.
Vomiting, airway obstruction, muscle spasms, writhing, grimacing, pulmonary oedema (of neurogenic or hypertensive origin), extreme hypertension.
Unconsciousness, raised intracranial pressure, widely dilated pupils (often fixed), uncontrolled twitching, and death unless artificial ventilation is provided.
After about 2 hours the muscle fasiculations and most symptoms start to subside, and are replaced with insidious but profound hypotension, primarily due to severe cardiac failure.
First Aid:
The pressure immobilisation technique MUST be commenced as soon as possible. Any delay risks the rapid onset of systemic symptoms. There have been no reports of deaths when effective first aid had been instituted.
The patient should immediately be evacuated to a medical facility capable of managing the envenomation. Treatment will require giving antivenom, providing artificial ventilation, and invasively monitoring the patient. Bandages MUST NOT be removed prematurely.
There is evidence that the venom may inactivated by prolonged localisation.
Medical Management
Institute intravenous access, adequate monitoring (iv, SpO2, non-invasive or arterial BP) and obtain antivenom BEFORE removing first aid bandages! An apparently well patient may suddenly deteriorate when they are removed.
The moment symptoms or signs of systemic toxicity develop, the antivenom should be administered intravenously. Supportive management, including oxygen, iv atropine, antihypertensives and sedation is usually required even if the antivenom is given. If the antivenom is administered early, the clinical situation is unlikely to get out of control.
Management of severe envenomation involves:
Airway control (intubation), administration of muscle relaxants, hyperventilation.
Invasive monitoring.
Gastric drainage (to prevent acute gastric dilation occurs).
Atropine iv to control cholinergic hyperactivity.
Sedation - benzodiazepines.
Anti-adrenergic agents early to control hypertension; later, inotropic agents and volume support - may require swan-ganz monitoring if difficult to manage.
Antivenom administration - one to two ampoules intravenously, slowly. May be repeated, according to response, at 10 to 15 minute intervals.
The antivenom is a highly purified rabbit IgG immunoglobulin and is highly effective; it should be given as soon as signs of significant envenomation are seen. Prophylactic adrenaline is not required, nor steroids, and there have been no reports of adverse reactions following its use.
Occasionally bites from the mouse spider or other atrax species may develop similar symptoms; if these are severe enough it may be useful to try funnel web antivenom.
Some more pics:
Sydney Funnel Web - Atrax robustus (39K jpeg)
Northern Tree Dwelling Funnel Web - Hadronyche formidabilis (31K jpeg)
Eastern Mouse Spider - Missulena bradleyi (33K jpeg)
More info is available from the AVRU funnel web pages.
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Red Back (Latrodectus mactans hasselti)
The adult female red back is about 2-3 cm long, quite black, with a distinctive red stripe on its abdomen. The male is much smaller and considered harmless. Neither are aggessive. Here's some general info from the Australian Museum.
Red back venom contains neurotoxins, but works very slowly. Fatalities, even from untreated bites, are rare.
The bite is immediately painful; the pain may involve the whole limb. Sweating is common, starting only on the affected limb. Systemic envenomation usually results in headache, nausea, vomiting, abdominal pain, pyrexia, hypertension and in severe cases, paralysis. Untreated, the symptoms worsen over a 24 hour period and may take weeks or months to resolve.
The pressure and immobilisation technique is NOT recommended as local pain may become excruciating. It may be relieved by the application of ice packs.
The red back specific anti-venom is reliable and is given to around 250 cases each year. It should be withheld unless signs of systemic envenomation develop, and if none occur with 24 hours is usually not required. However, if administration is delayed, it is still effective in relieving symptoms up to 10 days after the bite.
Antivenom may be given intramuscularly, because of the small volume involved. Adrenaline need not be given beforehand, unless the patient has prior exposure to equine antivenom or antitoxin or has an allergy to equine protein, in which case steroids should be given for four days as well.
Another pic:
Red Back Spider - Latrodectus mactans hasselti (31K jpeg)
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White Tail
The white-tailed spider (Lampona cylindrata), and bites from some other spiders, such as the common black window or house spider (Badumna species), the cupboard or brown spider, and (in the US)the brown recluse (Loxosceles reclusa) and hobo spiders (Tegenaria agrestis), have been infrequently implicated in the development of the so-called necrotising arachnidism syndrome, in which a near-painless bite progresses to painful cutaneous blistering and inflammation which may progress into intensely cyanotic lesions, occasionally resulting in substantial recurrent local tissue necrosis with a deep rolled ulcer involving fat and skin and exposing muscle. Amputation has been required for severe necrosis, and ulcer recurrence may last for years.
The precise cause is unknown, however it appears to be due to locally acting necrotising toxin (the recluse venom alone causes necrosis), probably in association with secondary infection. Approximately 25% of cases are associated with skin cultures positive for staphlococci . Strep pyogenes or mycobacterium ulcerans have been causatively implicated, however new evidence suggests that mycobaterium ulcerans may not play a significant role in the syndrome.Treatment depends on severity. Please review the literature.
If an area of redness and blistering develop, the limb should be elevated and the patient rested. No drug treatments, including antibiotics, have been clearly shown to be effective at this stage. Blisters may be cultured and a microbiologist needs to be involved to look for mycobacteria as well as other bacteria. Antibiotics should be administered on positive culture or on reasonable suspicion of secondary infection, however poor clinical response is to be expected. Lesions ahould be carefully observed; it may be a good idea to photograph them daily, and the patients temperature and general condition should be observed and recorded.
Should the situation deteriorate, the skin may start to look mottled or pale or bluish, or the redness and swelling may spread widely. This is unusual, but if it happens the patient needs admission to hospital. Ruling out serious secondary infection is advisable; this may include skin biopsy. The role of empirical antibiotic therapy is unclear. Should gangrene and/or skin necrosis occur surgical management may be appropriate, however early aggressive surgical therapy is not advocated. Hyperbaric Oxygen and Dapsone have been shown to be of benefit, mostly on data from treatment of experimental brown recluse venomation of animal models. It is probably worth discussing severe cases with the Venom Research Unit of the University of Melbourne. The AVRU site provides information about white tail spider bites and necrotising arachnidism. They are conducting a research sudy of necrotising arachnidism. "If you live in Australia, have been bitten recently (in the last few days) by a spider and have the spider that bit you, AVRU would like to hear from you. Please contact AVRU during office hours, or by mail or email, for further information about the study."
There has been some difficulty in clearly identifying the offending spider in cases of necrotising arachnidism. Convalescent serum (stored at -20C) may be tested against known spider venom components
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Snakes:
Australia's Venomous Snakes: The Modern Myth or Are You A Man Or A Mouse?
by Brian Bush
Author's Note: When concerning reptiles, the terms poisonous and venomous require redefining.
Poison is toxic if inhaled or ingested. The only poisonous reptiles known in Australia are the Green Turtle and the Hawksbill Turtle. More people have probably died on this earth as a result of consuming turtle flesh than ever has been the case from snakebite in Australia. There are no reported deaths from turtle poisoning here since 1945.
Venom is generally harmless if ingested but toxic when it comes in contact with the underlying tissue normally protected by the skin. Venomous animals have to break the skin with body-spines, stings or teeth (includes fangs in spiders and centipedes). The only venomous reptiles found in Australia are snakes.
For too long we have been telling the world, as well as each other, that Australia's snakes are the most venomous. On what evidence do we make this assumption? Solely on their ability to kill mice! What a joke!
The basis for the following discussion and points of view are personal experience, comments heard and questions asked during my time lecturing on venomous animals as well as a perusal of the relevant literature. I might just mention here that I have never lectured to mice!
I have heard it said many times by people I believe should know better that this or that Australian snake is "more deadly", "more toxic" or "more venomous" than the Indian Cobra (Naja naja). This is a misrepresentation of the facts and gains little support from the evidence available concerning humans. These types of statements have no place in education if positive results are the goal. All venomous snakes have the potential to be dangerous because of the variable sensitivity between individual people to venoms. However, first a bite has to occur.
Australian snakes are inoffensive and very shy. They have had only forty thousand years of human predation to contend with. None of their behaviour has evolved targeting humans. The traditional Aboriginal people only harvested the "quiet" nonvenomous snakes, rarely were the "cheeky" venomous species taken. Maybe this is why it is almost impossible to accidentally get bitten by one unless you run around the scrub in bare feet with your eyes shut, and half full on alcohol.
On other continents humans have existed for hundreds of thousands of years. Therefore, has the cobra evolved the hood, elevated stance and, in some species, the ability to "spit" venom as a direct response to human predation? What about the snakes that play dead? The Ringhals (Hemachatus haemachatus), one of a few "cobras" capable of spitting, also plays dead. This behaviour would have little effect in deterring a predator looking for a feed, but it may deter a passing human from taking up a club and clobbering the snake into lifeless pulp.
There is a widespread misconception that our snakes are very dangerous animals. Many of us do little to dispel this belief, maybe because we like to believe that Australia's snakes are the most dangerous. This is definitely the modern myth!
In the past 35 odd years I have met many people who believe tiger snakes have chased them. However, I have yet to meet someone that has been caught by one!
I often publicly comment that Australia's snakes are the deadliest in the world if you are a mouse. This is an objective statement supported by the available data. See Figure 1 for a true appraisal of which country/continent has the deadliest snakes.
Anyone perusing the literature will have seen reference to the LD50 using mice to measure relative toxicities of various snake venoms. This is great data if you are a veterinarian specialising in the treatment of snake-bitten mice! I believe it has little relevance when gauging the danger of a particular species to humans. The LD50 is scientifically indefensible in this regard. The snake currently ranking number one on that list has not been the cause of death to a human in any documented case history that I have seen. No doubt, Australia's medical scientists can take some credit for this. However, the Russell's Viper (Daboia russelli) found from Pakistan to China and Indonesia; the "lance-headed" group of pit-vipers (Bothrops spp.) of South America, the "saw-scaled" vipers (Echis spp.) of northern Africa, the Middle East, India and Sri Lanka are believed responsible for up to 50,000 deaths each year (Swaroop & Grab, 1954) and do not rank a mention. Maybe there has been no comparison made yet, or maybe they have venoms that are more dangerous to humans than to mice.
Number 24 on that list (Broad et al., 1979) is the Olive Whip Snake (Demansia olivacea). I believe it would have Buckley's chance of killing any human except maybe a decrepit old snake handler hypersensitive after years of continual exposure to venoms. All the LD50 does is compare the different venoms' toxicities on mice and is, therefore, biased towards mammal-specific feeders. To be more relevant each specific venom must have the LD50 criterion applied using a variety of animals such as fish, frogs and birds. Even then, the data collected would not reflect the toxicities of the respective venoms on humans. Mouse tissue is 50 times less responsive to Sydney Funnelweb Spider (Atrax robustus) venom than tissue from humans or monkeys (Underhill, 1988: 170). Kellaway (1934: 678) found that adult mice were unaffected by A. robustus venom. A worker could mistakenly judge this spider to be harmless when examining the LD50 toxicity of its venom on mice!
Remember also that Australia's snakes rarely envenom when biting defensively. Envenomation occurs in less than 1 in 10 bites (Sutherland & King, 1991: 1), or is it that a minority of people bitten experience systematic envenomation due to a hypersensitive reaction to the venom?
Many of Australia's venomous snakes such as Pseudonaja spp. do not even wait for their venom to immobilise prey. Instead, using constriction to restrain it, they often swallow it alive. I am of the opinion its primary purpose is digestion.
I can't help wondering, why has there been this preoccupation with the emphasis on exaggerating the danger of Australia's venomous snakes? Could it be that many of the researchers involved are government funded. They would have a vested interest in obtaining results that would most suit a favourable decision on continued funding.
It is probable that more people die each year in Australia from horse riding related accidents than snakebite. We do not go around hitting horses on the head with a shovel!
Those educators specialising in reptiles must definitely do all in their power to improve the snake's image. Rather than promote the negatives, emphasise the positives!
Figure 2 is from Sutherland (1992 & 1994), media reports and other sources to 1998. It presents the causes of snakebite believed to have resulted in 30 deaths in the past 18 years in Australia. An increased awareness of snakes through education and appropriate footwear could have reduced this by 16. A further reduction of 13.3% may have been possible if it was illegal to kill snakes. Four of the above victims may have still been alive today. The fact is that while the relevant wildlife authorities allow the killing of snakes they are directly contributing to the frequency of snakebite and therefore fatalities from this.
Both professional and amateur herpetologists must encourage a more positive attitude towards Australian snakes. This means less emphasis on the irrelevant laboratory tests of venom toxicity.
Those in a position of authority perpetuate many myths unknowingly. For example, some diving instructors continue to incorrectly refer to the "small mouth and rear fangs" in sea snakes. They often comment that sea snakes can only bite between the fingers or on the ear lobes. This is far from the truth (see Limpus, 1987 Pg 198). Zimmerman (1988) relates an experience where a Stokes Sea Snake (Astrotia stokesii) bites both a camera's strobe arm and a diving flipper thrust towards it. However, there are no documented fatalities in Australia from sea snake bite.
I once had an article refereed and returned with the comment that "...... Australia's elapids have grooved fangs". Along most of the fang's length this "groove" is a closed seam, only being opened towards the tip where it does not detract significantly from the fang's function or effectiveness.
Many people make an erroneous distinction between tiger snakes' (Notechis spp.) fangs and Taipans' (Oxyuranus scutellatus), saying the former differ by being grooved. The only distinction is the length, in both species they are effectively hollow.
On another occasion and another referee a problem with semantics arose in reference to the words "dangerously venomous". The comment came back. "...delete dangerously, you already have venomous". These terms are far from synonymous!
We strive for objectivity but when dealing with snakes, subjectivity commonly comes to the fore. Many believe the widespread fear of these animals is a result of teaching but, after working with aborigines, I think that in many of us our fear is instinctive. On top of this we have the added burden of the way snakes have been portrayed historically. Moses, in the Book of Genesis, symbolised evil as a serpent. As snakes were the bad guys already he wasn't treading on any toes. The mythical Medusa and Cleopatra do little to improve the image.
To increase people's awareness and improve the snake's image in Australia much more positive information must be available in any educational session. Maybe this will encourage people's want to conserve them.
I am of the opinion that changes to the relevant Policies and Acts allowing the killing of snakes need to occur to place more responsibility on the person to justify the killing. The respective wildlife authorities have only limited resources for the education needed to bring about this type of change. However, both amateur and professional herps, with our altruism are ready to go. Tread carefully though, do not fall into the trap of perpetuating the myth just because someone else did.
Ponder On This
One of a government's responsibilities is to protect its people. In allowing the killing of venomous snakes it contributes towards snakebite resulting in injury and death. Therefore it may be negligent in its responsibility by continuing to endorse open seasons or similar.
The LD50 Described
The LD50 is a standard laboratory test with set guidelines laid down by the World Health Organisation. With the toxicity test in snakes, individual mice within a sample receive equivalent quantities of venom (each mouse is of the same weight). Each sample receives less venom than the previous. The LD50 is the amount of venom administered to each mouse to cause 50% of the sample to die. The lower the LD50 the higher the toxicity is on mice!. For the limitations and problems with this type of test see White (1987).
The Answers To Some Common Questions
Australia's most venomous (yield) snake is the King Brown (Pseudechis australis). Believed involved in very few fatalities.
The most toxic snake venom on mice (of the species tested) is the Inland Taipan (Oxyuranus microlepidotus). See Figure 3.
Australia's deadliest snakes are the brownsnakes (Pseudonaja spp.). Believed involved in 18 of the past 28 deaths attributed to snakebite. See Figure 4.
The world's deadliest snake, based on documented deaths, is probably the Saw-scaled Viper (Echis carinatus) especially in Sri Lanka. The deaths of nearly fifty people per million from snakebite occur there each year. Today in Australia we have 0.13/million deaths each year. See Figure 1.
The most misrepresented data by the Australian herpetological community is the list of snakes showing their lethality on mice compiled by Broad et al (1979). Often presented as if it directly relates to humans. It does not.
Acknowledgment
I thank Pat Garland for his critical appraisal and constructive comments on this article, much of which comes from the heart not the head.
References
BROAD, A.J., SUTHERLAND, S.K. & COULTER, A.R 1979. The lethality in mice of dangerous Australian and other snake venom. Toxicon 17: 661-664.
KELLAWAY, C.H. 1934. A note on the venom of the Sydney Funnelweb Spider Atrax robustus Med. J. Aust.. 1: 678-9.
LIMPUS, C. 1987. Sea Snakes. Pp 195-204 In Toxic Plants & Animals, a Guide for Australia.. (Eds. J. Covacevich, P. Davie & J. Pearn) Queensland Museum.
MUNRO, D. 1988. Chambers World Gazetteer. 5th Edit. Chambers & Cambridge, International.
PARRISH, H.M. 1963. Analysis of 460 fatalities from venomous animals in the United States. Amer. J. Med. Sc. (Feb).
SPAWLS, S. & BRANCH, B. 1995. The Dangerous Snakes of Africa.
SUTHERLAND, S.K. 1992. Deaths from snake bite in Australia 1981-1991. Med. J. Aust. Vol. 157: 740-746.
SUTHERLAND, S.K. 1995. Snakebite deaths in Australia 1992-1994 and a management update. Med. J. Aust. Vol. 163: 616-618.
SUTHERLAND, S.K. & KING, K. 1991. Management of snake-bite injuries. RFDSA Monograph Series 1: 1-12.
SWAROOP, S. & GRAB, B. 1954. Snake bite mortality in the world. Bull. of World Health Organisation 10: 35-76.
TRINCA, J.C. 1963. The treatment of snake bite. Med. J. Aust. 1: 275-280.
UNDERHILL, D. 1988. Australia's Dangerous Creatures. Readers Digest, Sydney. 368pp.
WHITE, J. 1987. Elapid Snakes: Venom Toxicities and Actions. Pp 369-89In Toxic Plants & Animals, a Guide for Australia. (Eds. J. Covacevich, P. Davie & J. Pearn) Queensland Museum.
ZIMMERMAN, K.D. 1988. The question of sea snake aggression. Herpetofauna 18(2): 11.
Figure 1. A comparison of annual snakebite fatalities per million people from around the world. To standardise comparisons published data compiled between 1945-1960 used. Australia's current figure is 0.13 per million however for relevant period used here it was 0.45 per million.
Venom toxicity is only one of many contributing factors determining how dangerous a particular species is. Australia's snakes pale to almost insignificance when compared to the fatalities caused by their counterparts in other parts of the world. The above figures are very conservative for the developing countries sampled, eg, West Africa has recently been found to have 23,000 deaths each year with less than 10% of victims being treated in modern medical facilities (Spawls & Branch, 1995). Many victims probably die in the bush and are not included in any sample. The 23,000 figure may be very conservative!
Data for USA from Parrish (1963); Africa, India and South America from Swaroop & Grab (1954); and Australia from Trinca (1963). Populations are from Munro (1988).
Figure 2. Comparing the relative frequency of causes of snakebite in Australia resulting in the deaths of 30 people over a 18 year period (from Sutherland, 1992 & 1994 and media reports for 1993-98).
Accident - unavoidable without exceptional awareness.
Herp - herpetologist bitten while handling snake.
Kill - bitten while killing snake.
Mis ID - bitten while handling venomous snake believing it to be harmless.
Trod - bitten after treading on snake.
? - insufficient data to determine cause.
LETHALITY IN MICE
From Broad, Sutherland & Coulter (1979)
(In descending order including LD50 in mg/kg. In first figure venom diluted in saline solution only, 2nd includes the addition of a blood protein, bovine serum albumin)
Inland Taipan (Oxyuranus microlepidotus) 0.025 0.010
Eastern Brown Snake (Pseudonaja textilis) 0.053 0.041
Northern Taipan (Oxyuranus scutellatus) 0.099 0.064
Eastern Mainland Tiger Snake (Notechis s. scutatus) 0.118 0.118
Reevesby Island Tiger Snake (Notechis ater niger) 0.131 0.099
Beaked Sea Snake (Enhydrina schistosa) 0.164 0.173
Western Mainland Tiger Snake (Notechis scutatus occidentalis) 0.194 0.124
Chappell Island Tiger Snake (Notechis ater serventyi) 0.338 0.271
Southern Death Adder (Acanthophis antarcticus) 0.400 0.338
Copperhead (Austrelaps superbus) 0.560 0.500
Indian Cobra (Naja naja) 0.565 0.500
Black Mamba (Dendroaspis polylepis)
Dugite (Pseudonaja a. affinis) 0.660 0.560
Papuan Black Snake (Pseudechis papuanus) 1.09 1.36
Stephens's Banded Snake (Hoplocephalus stephensii) 1.36 1.44
Rough-scaled Snake (Tropidechis carinatus) 1.36 1.09
King Cobra (Ophiophagus hannah) 1.80 1.91
Spotted Black Snake (Pseudechis guttatus) 2.13 1.53
Collett's Snake (Pseudechis colletti) 2.38
King Brown Snake (Pseudechis australis) 2.38 1.91
Red-bellied Black Snake (Pseudechis porphyriacus) 2.52 2.53
Small-eyed Snake (Cryptophis nigrescens) 2.67
Olive Whip Snake (Demansia olivacea)
Eastern Diamond-backed Rattlesnake (Crotalus adamanteus) 11.4 7.70
Figure 3. The most widely misrepresented data concerning venomous snakes in Australia. It is usually stated that this ranking is an undisputable reflection of dangerousness.
Figure 4. Comparative frequency of fatalities relative to the five species of snake believed involved for the 18 year period 1980-1998.
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