Over time many species of death adder have been considered and disregarded with numbers ranging anywhere from 4 up to 15 (see species below).
Early Australian settlers called them the "deaf adder" due to their ambush hunting style and the fact they would stay motionless if approached, leading to the idea that these snakes couldn't hear. However like other snakes the death adder is in fact capable of perceiving ground vibrations.
Death adders are mainly nocturnal and terrestrial animals, they usually remain under cover during the day, very often close to pathways where small animals and people commonly wander. They usually rely on their camouflage and remain still ,but if provoked they flatten their body in a coiled position and will strike swiftly, only if this fails it resorts to escape.
The genus name, Acanthophis, derives from the Ancient Greek acanthos meaning "spine" and ophis witch means "snake", and refers to the spine found in it's tail.
The death adders have a very similar appearance to vipers or pit vipers, with a short and robust body, narrow neck, triangular shaped head and a tail spine. There is a slight sexual dimorphism with females being marginally larger than the males, the species reaches adult size at 2 or 3 years of age.
The several species reach adult sizes ranging from 1,15 ft (35 cm) for the smaller and slender bodied Pilbara Death Adder (Acanthophis wellsei) to a maximum of 4,25 ft (130 cm) for the Barkly Tableland Death Adder (Acanthophis hawkei). But death adders usually don't reach more than 3,25 ft (100 cm).
Just like size, colouration varies among species depending on their habitat, ranging from brown, black, greenish-grey to grey or red and yellow, many specimens have large bands wrapping the body.
The scales also vary from smooth or moderately keeled to strongly keeled like in the Rough-scaled Death Adder (Acanthophis rugosus).
Despite their name they aren't true adders and even though they have a striking resemblance to vipers (Viperidae), they in fact belong to the Elapidae family.
Death adders are more closely related to the deadly taipans, african mambas, cobras or even coral snakes. This similarity in appearance of snakes living half a world away is due to a phenomenon called convergent evolution.
Species / Taxonomy
There’s some controversy about exactly how many death adder species exist and it's still unclear how many species the genus should include. There were traditionally only 3 species recognized but in 1998 5 new species were described with 3 more described in 2002.
Most of these new species weren't widely accepted. In 2015 DNA studies revealed one more species the Kimberley death adder (Acanthophis cryptamydros), so the species taxonomy is likely to change again.
These are the most commonly found in literature and widely accepted:
Common death adder (A. antarcticus) - Found only in eastern and coastal southern Australia and Papua New Guinea.
Northern death adder (A. praelongus) - Found only in Australia.
Desert death adder (A. pyrrhus) - Found only in Australia from the Western Australia coast to south central regions and into the Northern Territory.
Pilbara death adder (A. wellsi) - Found in Australia in Hamersley and Chichester Range of the Pilbara.
Seram death adder (A. ceramensis) - Found Indonesia's Seram and Tanimbar islands.
Kimberley death adder (A. cryptamydros) - Found in the northwestern corner of Australia.
Barkly Tableland death adder (A. hawkei) - Found only in Tasmania.
Smooth-scaled death adder (A. laevis) - Found in in Indonesia and Papua New Guinea.
Rough-scaled death adder (A. rugosus) - Found in Indonesia, Papua (Irian Jaya) and Australia's Northern Territory, Western Australia and northwest Queensland.
Venom / Bite
Being among the deadliest snakes in the world it's still unique because unlike most venomous snake species the death adder venom contains no haemotoxin or myotoxins it's completely neurotoxic.
The death adder has longer and more mobile fangs than most elapid snakes, still much smaller than the fangs of some of the true vipers like the gaboon viper. They can inject anywhere from 40 to 100 mg of their highly toxic venom in a single bite, and about 60% of bites result in significant envenoming and require antivenom therapy. Putting them among the most dangerous australian snakes.
A death adder bite first symptoms are nausea, drooping eyelids, muscle weakness, speech difficulties and minor paralysis symptoms. But these can progress to breathing difficulties and full respiratory failure, leading to death in 6 hours.
The LD50 value of their venom was reported as 0.4 to 0.5 mg/kg subcutaneous, and before antivenom was introduced about 50% of bites proved fatal. Because of the slow progression of envenomation symptoms and today's wide availability of anti-venom deaths have become rare in Australia but they are still the cause of many snakebites and deaths in New Guinea.
The specific death adder antivenom works rapidly and the reversal of symptoms from bites is faster than with other snake species like the taipans or tiger snake.This is due to the fact that with other venomous snake bites several types of effects are experienced like haemotoxin and/or myotoxic effects, not only neurotoxic.
Diet / Feeding
The various species of death adder feed mainly on small mammals, rodents, lizards, frogs and birds. Unlike other snake species they don't actively hunt, the death adder buries itself among soil, leaf litter or sand, leaving only the head and tail exposed, but still very well camouflaged.
They use the end of the tail for caudal luring, wiggling it to attract prey. They then lie and wait often for several days until a victim passes near by.
Their ambush hunting tactics and camouflage means the death adder is a bigger threat to humans. Whereas other snakes will flee at the first sign of danger the death adder relies on it's camouflage and will usually stay put.
With probably the fastest strike of the world, it's typically to late when the snake is spotted if unsuspectingly we venture to close to it. They are able to strike in less than 0.15 seconds. However the death adder is really reluctant to bite humans, and normally only does so in self-defence.
The females give birth to large litters of live hatchlings in late summer. Although an average of 10 to 20 newborns is the usual, there are records of over 30 young in a single litter.
Conservation / Threats
The death adder population numbers in Australia are falling mainly due to habitat destruction and the introduction of feral animals such as foxes and cats. The death adder also faces the threat of the poisonous cane toad, introduced to Australia in the 1930's (to eat beetles), when native animals eat it they get a toxic or even lethal dose of its poison.
Death adder species found in Indonesia and Papua New Guinea have stable population number and face no major threats. These snakes are not listed under CITES and don't have a protected status.
Did You Know?
The Mojave rattlesnake venom is regarded as the most toxic of any rattlesnake because of the presence of the "Mojave toxin".