A rare animal that is a long way from home

The De Vis' Banded Snake (Denisonia devisi) is thick-set and relatively coarsely-scaled snake that grows to a little over half a metre.  It is active chiefly at night when it hunts small vertebrates, mainly frogs, and shelters during the day under leaf-litter, fallen logs and in cracks in the soil.  Its venom is highly toxic.  The only record for this species is from far north-western Victoria near the Murray River.  The De Vis' Banded Snake is classified as vulnerable in Victoria.

In 1856 a young German zoologist, Gerard Krefft, joined an expedition lead by, William Blandowski, the Curator of the Melbourne Museum, to explore the country around the junction of the Murray and Darling Rivers.  Along the way they passed through Lake Boga, 10 km south of Swan Hill, and Krefft recorded a Common Death Adder (Acanthophis antarcticus).  This species was known from Victoria and was considered, by Frederick McCoy (also of the Melbourne Museum), to be relatively common along the Murray in the state's north-west.  Indeed the Museum's Ludwig Becker had, a few years earlier, created a detailed illustration from a specimen he collected somewhere near the Murray.  Despite this apparent common knowledge of the species, however, Krefft's find was the only one which included a specific location.  The specimen was roughly treated, and almost decapitated, before being immersed in preserving fluid and eventually (according to Krefft) found its way to the Melbourne Museum.  Unfortunately the specimen was then lost or mislaid.  He did, however, provide a reasonably good description of the snake in his expedition notes and apparently illustrated both the characteristic head and tail.  The illustration disappeared as well.   

This species was apparently never seen in Victoria again.  Nevertheless Victorian zoologists have accepted Krefft's identification and the view that Death Adders were once common along the Murray.  The Death Adder is only one of several species, such as the Bridled Nailtail Wallaby and the Brush-tailed Bettong which Krefft saw many of along the Murray Valley and have since become extinct. 

In 1994 a biologist working for the Victorian government recorded another Common Death Adder from Walpolla Island, about 20 km west of Mildura near the Murray River, once again there was no verifiable specimen collected.  Coincidentally, this record was about 10 km west of the confluence of the Darling and Murray Rivers, where the Blandowski Expedition set up its base camp.  Both Death Adder locations are several hundred km away from any modern confirmed records.  In South Australia the nearest record is from coastal regions north of Adelaide, and the nearest records from NSW are from near coastal regions in the far south-east - one site, from 1971, is within a kilometre of the Victorian border in vegetation that extends well into this state.  Logic would tell us that if Death Adders were indeed to be found in Victoria then far East Gippsland is a much better option than the north-west.  Nevertheless, the 1994 sighting piqued the interest of Victorian herpetologists and in late 2005 a small team of them, lead by Nick Clemann and Peter Robertson, carried out a thorough search of the Walpolla Island site.

What the herpetological team found was not a Common Death Adder but a De Vis' Banded Snake and this time the identification was confirmed by photographs and by lodging specimens with the Victorian Museum.  The two species are fairly closely related and look superficially alike.  Both have broad heads and abruptly tapered tails, and both have alternating bands of light and dark brown along their bodies. It is not surprising then, that the animal was misidentified, particularly if the observer didn't get very close.  The other thing the snakes had in common was that the nearest confirmed record was hundreds of kilometres away,  The Banded Snake was previously known only from NSW and Queensland, and the nearest confirmed sighting is nearly 500 km to the north.  There were, however, two other unconfirmed locations which weren't so far away.  One from about 40 years ago, 100 k north of Wentworth, (the town on the Darling-Murray confluence) and more recently another from Wentworth itself.

It is tempting for a modern observer to suggest that an otherwise northern species finding its way to Victoria is a little piece of evidence that backs up some of the global warming theories.  However, it may have been that Krefft made an error in his notes (the Blandowski Expedition was famously disorganised) and that his record was from the Wentworth base camp, not Lake Bolac, and was actually a De Vis' Banded snake - the species was not described until 1920 so he wouldn't have seen one before.  However, that part of the story has been sorted out quite recently, once again by Nick Clemann and his colleagues.  The lost Death Adder specimen was not lost at all. It is still in the Melbourne Museum's collection, clearly labeled and possibly in the original jar - museum's rarely throw specimens away.  Krefft's illustration, on the other hand, was taken back to Prussia by Blandowski when he returned home a few years later.  It now resides in Zoologisches Museum, Berlin, and digital images of it match almost perfectly with the specimen in Melbourne.