WHY DEATH ADDERS (ACANTHOPHIS ANTARCTICUS) ARE ALMOST CERTAINLY NOT A PART OF VICTORIA'S SNAKE FAUNA.
488 Park Road
Park Orchards, Victoria, 3114, Australia.
Originally Published in Bulletin of the Chicago Herpetological Society 44(8)(August 2009):125-128.
Evidence suggests that contrary to the speculation of many people, Death Adders (Acanthophis antarcticus) are not a part of the Victorian (Australia) fauna. This paper provides the factual evidence in terms of these snakes not being in the Australian state of Victoria.
Death Adders (Genus Acanthophis) are unique among the family Elapidae in that their appearance and biological habits have evolved in a manner convergent with viperid snakes.
Included is the stout body, ambush predation as a feeding strategy and use of a caudal lure as part of their ambush predation (Chiszar, et. al. 1990, Hoser 1995).
In Death Adders the lure takes the form of a modified scale at the end of the tail terminating in a spine (see Carpenter et. al. 1978). The latter part of the tail is often of a different colour to the rest of the snake, including being sometimes white, cream, or black (see Hoser 1989 for photographs of examples).
They are found in all mainland Australian states except for Victoria (see below), including islands off the coasts in SA, Western Australia, northern Australia, Torres Strait, New Guinea and islands west of there (see Hoser 1998 and Hoser 2002).
The species is not known from Victoria, although it's occurrence has been suspected or speculated along the northern border of the state, especially in the north-west and north-east.
There are some isolated and unconfirmed records for Victoria, however the basis of this paper is to suggest that the species may never have occurred in this state at any time since European settlement, or if so, then it is no longer in this state in any area.
The best known citations for Death Adders in this state are as follows.
1. A line drawing by Gerard Krefft, of a specimen allegedly from Lake Boga, in the Murray Valley, northern Victoria. The drawing was made in 1856 in his diary and little is known of the basis for it. No suitable habitat for the species exists in the area and it's thought that if it was there in the first instance, then the population has long since been extinguished (see Coventry and Robertson 1991). However another very real possibility and one countenanced by myself is that the record may have been in error and/or the specimen may have originated from somewhere else. Evidence for this is the continued absence of the species from apparantly suitable habitat west of this location in the Sunset Country National Park in Victoria.
2. Another record of note is that of an alleged specimen found on Walpolla Island in the Murray Valley, north-west Victoria. No specimen was retained and the sighting was by Peter Menkhorst who said he identified the snake after checking in a relevant herpetological field guide. This claim is disputed on the basis of a lack of a specimen, no further specimens being found in the area, a general lack of suitable habitat for the species on the island and the fact that the species may be confused with others known to occur in the area, most notably Tiger Snakes (Notechis).
3. There are regular news reports of Death Adders turning up in areas around Albury-Wodonga, along the Murray River. Within the five years to 2003 there was a report of one such snake in the local paper (The Border Mail) replete with a photograph of the said snake. The snake was merely a Tiger Snake (Notechis scutatus) and a very normal one at that. No records of Death Adders from the Albury Wodonga area have checked out as true and based on the known habits of the species and the local habitat, which is totally unsuitable for the species, any claims of Death Adders in the area must be treated with the utmost skepticism.
4. Coventry and Robertson (1991) speculate that the species may still be present in coastal heaths of far east Gippsland, as Death Adders are found in similar habitats on the south-east coast of NSW. This speculation is discounted here on the basis that the relevant areas near Genoa and Mallacoota are heavily collected by private herpetologists, including at least one who has lived in the area for some years (Clinton Logan) and yet none has turned up any evidence of the species in Victoria. The closest known locations are coastal heaths north from about Eden, NSW (including as cited in Longmore 1986), where these snakes are both common and commonly seen.
5. Swan 1990 reports on a record in New South Wales from the Bondi State Forest (20 minutes drive south of Bombala, NSW) and within a short distance of the NSW/Victorian border. This record does not appear in Longmore (1986) and I have no knowledge of the basis for the record. While there is apparently suitable habitat for Death Adders in the area, the Bondi State Forest record and any others from the area must be doubted as the area is generally colder than other areas inhabited by the species and by a significant margin based on altitude. The idea that these snakes are found in suitable habitats inland from coastal heaths that apparently lack the species also flies in the face of what is known about the distribution of these snakes in places such as south-eastern South Australia.
Notwithstanding the published records and speculation as given above, the known distribution of Death Adders in south-east Australia as of 2003 leads to the conclusion that Death Adders have not been in Victoria at any time since European settlement and probably for quite some time beforehand.
The basis of this conclusion can be seen from the distribution of these and other species of elapids, including species as well-known as Tiger Snakes (Notechis) and Copperheads (Austrelaps) and a reconciliation of these known facts with other data such as climatic for south-east Australia.
MODERN DISTRIBUTION OF ELAPIDS IN SOUTHERN AUSTRALIA
In the recent geological past (the last 20,000 years), Australia's climate has got progressively warmer. The result of this has been a receding of the distributions of cold-climate genera/species of snake such as Tiger Snakes (Notechis) and Copperheads (Austrelaps).
In terms of Tiger Snakes, their distribution has become disjunct across southern Australia with the Eastern and Western populations becoming split as the Nullabor Region of southern Australia has become too hot and dry for them. In Queensland at least one outlier population has formed at high altitude in the Canarvon region, being cut off from the others by a region of warmer lowlands.
For the Copperheads a similar situation has occurred.
The distribution in northern New South Wales, in the New England Tableland has become disjunct and restricted to cooler high-altitude locations. The Victorian population enters South Australia near Mount Gambier, then is cut off from the other population of Copperheads in the Adelaide Hills and Kangaroo Island by an area of relatively warm lowlands.
Noting the stark differences between the regional variants of Copperheads in southern Australia, it appears that periods of warming and cooling in Australian climate have occurred at least twice over the recent millenia.
Geological records confirm the same in other parts of the world.
Other cooler climate species (or genera) to have their distributions broken up into disjunct populations include the Rough-scaled Snakes (Tropidechis) and the Red-bellied Black Snakes (Pseudechis), whose Queensland populations have formed outliers in the montane areas.
Noting that the climate has warmed over the last 20,000 years, it is not surprising that cool climate species have tended to have their distributions decline and become fragmented.
However in terms of warm climate species in southern Australia, the reverse has evidently been the case.
For King Brown Snakes (Cannia australis) the distribution appears to be more-or-less continuous extending southwards from warmer parts of northern Australia.
Death Adders also appear to have expanded their distribution southwards in the recent past in southern Australia and within their known present range, their distribution is effectively continuous (as befits a species with an expanding range). This of course discounts the effects of the removal of habitat since European settlement.
It is also notwithstanding the two known populations of A. antarcticus being themselves separated. These populations are the one in the Eastern states, centered along the NSW and Queensland coasts and the other starting in South Australia from the Gulf of St. Vincent and extending west from the Eyre Peninsula, more or less continuously to the south-west of Western Australia.
That temperature has been the principal determinant of distribution is indicated by the distribution of the species in South Australia and New South Wales.
In both states, the southernmost known populations tend to be found at or adjacent to coastal heaths that are protected from the cold by a moderating sea influence.
In terms of South Australia, these snakes are found further south along the Gulf of St. Vincent on the warmer western side than on the cooler Eastern side.
Using this criteria alone, the only likely places in Victoria that the species could be found are in the far north-west or the far north east along the coast.
Both areas are heavily surveyed by reptile collectors and have not yielded Death Adders. It's also known that where these snakes occur, they do occur in large numbers are generally well-known by local inhabitants. As this is not the case for either part of Victoria, it must therefore be concluded that these snakes are not present in these regions.
In terms of north-east Victoria, the picture seems self-evident. The range of these snakes had not extended to the north-east of Victoria, even if in the recent past, the climate and other factors made the habitat suitable for them.
It is also worth comparing the Death Adders with a somewhat more mobile snake species that has also extended it's range southwards in the recent geological past. The Diamond Snakes (Morelia) have only managed to just cross the NSW/Victorian border and are not found in areas of apparently suitable habitat further south. These snakes are also found in colder parts of the Blue Mountains in New South Wales than Death Adders (e.g. on top of the Newnes Plateau), which may also in part explain their distribution running further south than that of the Death Adders.
Another noteworthy variable is fire.
Death Adders are also slow moving and hence relatively unable to flee bushfires. Hence areas without hills, rocks or large gaps in vegetation are likely to burn totally if on fire and kill all or most Death Adders.
Throughout southern Australia, Death Adders tend to be found at or near areas that have refugia to fire and their distribution tends to reflect this fact. The range has tended to expand along coasts and ridgelines.
Even as far north as Sydney, Death Adders are not found on the Cumberland Plain which as a natural habitat provides no refuges for these snakes during fires. They do however survive quite well in hilly and coastal areas with natural retreats from flames. The same situation is seen in the plains immediately west of Brisbane city in the Ipswich region.
The fire factor may also explain why Death Adders have been rare or absent in western New South Wales, even before the time of European settlement.
There are only a few records of the species from inland New South Wales, all are very old and all are from hilly areas. However these snakes are known from inland areas of Queensland, where habitat was more heavily wooded in the pre-European period.
The patchy distribution of Death Adders in the Darling River Basin appears to go against the idea of a warm climate species expanding it's distribution. However if reconciled with the recent arrival of Aborigines (in the last 40,000 years) and a changed fire regime as a result, it seems likely that by changing the vegetation cover in these areas through fire and perhaps increasing numbers of certain grazing animals at different times, that Death Adders may well have found themselves in areas now made unsuitable for them.
Hence they died out in this area and their distribution became patchy.
They are relatively unusual among Australian snakes in that they cannot tolerate habitat modification and rely on a thick matting of leaves or other vegetation litter in order to survive.
Areas heavily grazed by native or domestic animals are rendered unsuitable for these snakes and they die out.
This may well explain the patchy distribution of these snakes in inland NSW and further north in inland Queensland in the time of immediate post-European settlement.
WHY THERE ARE NO DEATH ADDERS IN NORTH-WEST VICTORIA
In the far north-west of Victoria, in the region generally known as Sunset Country is a vast belt of habitat that is evidently suitable for Death Adders. The present day climate appears to be warm enough for the snakes, as evidenced by them being found in similar parts of Western Australia. Furthermore the habitat appears to be optimal in that it has sandy or rocky soils, stunted gum trees, spinifex tussocks and so on.
In spite of these facts and the fact that the area is heavily collected by herpetologists, no Death Adders have turned up.
That there are no Death Adders here is confirmed by a similar absence of these snakes in other areas of suitable habitat to the immediate north in New South Wales and to the immediate west in places like Renmark, South Australia, the latter being inhabited by the snake collecting Bredl family for many years.
If there had been Death Adders there, then the Bredl's would have found them.
Instead they used to travel to places like Whyalla on the Eyre Peninsula to get their stock.
The obvious question then becomes why no Death Adders?
Based on what's already known about the local climate, it is reasonable to infer that the north-west of Victoria was not always suitable habitat for these snakes.
Furthermore the main basis for the claim that the area is now optimal habitat is the presence of more than one variety of Spinifex (Triodia spp.) in the area.
However what appears to have been missed by many commentators is how these species of grasses get to be in these areas.
Most importantly, Spinifex seeds are light and may be transported via the wind. During summer dust storms which occur most years, seeds and the like may be transported many hundreds of kilometers through the air before being deposited on the ground. By way of example, the entire north-west of Victoria is covered with reddish sandy soil (bulldust) to an average depth of some feet even though the locally occurring rock is white. The soil is blown in from central Australia and parts of Western New South Wales.
Hence, it's obvious that in the recent geological past, Spinifex has also been blown into these parts of Victoria.
Spinifex can only grow in stony and sandy habitats and these grasses don't grow on low lying river flats, floodplains, black soiled areas and other situations.
In other words the species is able to jump vast areas of unsuitable habitat.
By contrast, Death Adders can't do this.
Even in areas of good habitat, these snakes more than any other Australian reptile are known for one trait … not moving.
Furthermore, recent DNA studies on West Australian Acanthophis wellsi and A. pyrrhus by Ken Aplin and Steve Donnellan (1999) and venom-related studies by Fry et. al. (2001) on several species have indicated that even close populations have been separated for some time, indicating the lack of mobility for these snakes, even across short distances.
Additional evidence of the lack of mobility of Death Adders comes from their distribution in Southern Australia. They are found on islands off the coast, including Revesby Island, South Australia and others off the WA coast, which have all been disconnected from the mainland in the last 12,000 years or less and in terms of SA, there is little evidence to suggest much expansion south of the species in the time frame since then, even though evidence suggests that the changes in the local climate could have facilitated a reasonable south-ward expansion of their range beyond that which we know exists.
IS THE DEATH ADDER RARE IN VICTORIA?
Finally there is the theory bandied about that because Victoria lays on the edge of the potential range for the Death Adder species, that it may be either rare here or harder to find. Worrell 1972 was one proponent of this theory.
However there is no basis for it.
By contrast, in the most southern parts of the known range for Death Adders in places like Revesby Island and Ardrossan, South Australia, these snakes are particularly common and easy to find. In terms of the Diamond Python (Morelia spilota) a NSW species which also occurs on the Victorian side of the state border at Mallacoota, Genoa and nearby areas, it too is easy to find in these places, which happen to lie at the southern edge of the known range of the species.
By virtue of their ecology and habitats, it is fairly safe generalization that where Death Adders occur they are common. Even if not easy to find by collectors on a given day, these snakes are found if looked for enough and they are regularly seen, caught and identified by non-herpetologists. Once again, I note none have turned up in Victoria and hence the only inference can be that they are not here.
Also of note is that while much of Victoria's habitat has been altered since European settlement, the two areas of likely habitat near the NSW border in the North West and North-east are effectively unchanged and hence if they had Death Adders 200 years ago, they still would have. It is for that reason that old records and claims of Death Adders must be dismissed as either hoaxes or inaccurate.
The Death Adder in Victoria has become somewhat of a Holy Grail, much in the same way as the Thylacine in mainland Australia. It's become a status symbol to claim to know they are in the state or to have found one once. However the evidence of the species occurring in this state is absent and unless and until a population is identified here, the species should be regarded as being absent from the state's fauna now and at all other materially relevant times since European settlement of Australia.
The evidence of suitable habitat in Victoria for Death Adders cannot be taken as evidence of the snakes occurring in this state. The fact that none have been found in spite of extensive collecting of reptiles in the only areas of suitable habitat in the north-west and north-east of the State must be taken as showing that Death Adders do not occur in Victoria.
If the snakes were in Victoria, they would have been found and based on the size of the areas of apparently suitable habitat, could be collected at will.
The distribution of Death Adders in southern Australia has expanded in recent geological times, but had not yet reached Victoria at the time of European settlement. Since European settlement of Australia the possibility of the species expanding it's range into Victoria has been removed, other than via a deliberate and planned introduction of specimens into an area. This is not foreseeable.
Carpenter, C. C., Murphy, J. B. and Carpenter, G. C. 1978. Caudal luring in the Death Adder (Acanthophis antarcticus (Reptilia, serpentes, elapidae)). Journal of Herpetology 12:574-577.
Chiszar, D, Boyer, D., Lee, R., Murphy, J. B. and Radcliffe, C. W. 1990. Caudal luring in the southern death adder, Acanthophis antarcticus. Journal of Herpetology 24(3):253-260.
Coventry, A. J. and Robertson, P. 1991. The Snakes of Victoria. Department of Conservation and Environment, East Melbourne, Victoria, Australia. 75 pp.
Fry, B. G., Wickramaratna, J., Jones, A., Alewood, P. F., and Hodgson, W. C. 2001. Species and Regional Variations in the Effectiveness of Antivenom against the in Vitro Neurotoxicity of Death Adder (Acanthophis) venoms. Toxicology and Applied Pharmacology 175:140-148.
Hoser, R. T. 1989. Australian Reptiles and Frogs. Pierson and Co., Sydney, NSW, Australia:238 pp.
Hoser, R. T. 1995. Australia’s Death Adders, Genus Acanthophis. The Reptilian 3(4):7-21 and cover, 3(5):27-34.
Hoser, R. T. 1998. Death Adders (Genus Acanthophis): An overview, including descriptions of Five new species and One subspecies. Monitor - Journal of the Victorian Herpetological Society 9 (2):Front Cover, 20-41.
Hoser, R. T. 2002. Death Adders (Genus Acanthophis): An updated overview, including descriptions of 3 new island species and 2 new Australian subspecies. Crocodilian - Journal of the Victorian Association of Amateur Herpetologists 4(1):5-11,16-22,24-30, front and back covers.
Longmore, R. 1986. Atlas of Elapid Snakes of Australia. Australian Government Publishing service, Canberra, ACT, Australia:120 pp.
Swan, G. 1990. A field guide to the Snakes and Lizards of New South Wales. Three Sisters Productions, Pty, Ltd, Winmalee, NSW, Australia:224 pp.
Worrell, E. R. 1972. Dangerous snakes of Australia and New Guinea. Angus and Robertson, Sydney, Australia. 65 pp.
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