About the Bobuck Underground
What are Bobucks?
The Bobuck, Trichosurus caninus or Trichosurus cunninghami is also known as the Black Possum or the Mountain Possum. As one of its names suggests, it is typically found only in mountain country of eastern Australia. It is adapted to endure the extreme cold of winter in the Great Dividing Range above the snow line. Its short ears, dark, almost black coat and large body size with "stumpy build", are adaptations wrought by Natural Selection that help to minimise loss of body heat. Evolution has thus produced an animal that is well able to cope with the harsh conditions of its snow-clad mountain home. Like all possums, it is a marsupial.
The Discovery!
In 2005 my automatic, infrared-activated cameras photographed a Bobuck in a reedy creek on Westernport. What was it doing so far from its usual haunts? What's more it was not the only one. I returned a week after this historic first photograph and collected over a dozen more shots of them. There is an entire population here along the shores of Westernport that had never been hitherto reported in scientific literature.
Where are The Gurdies?
An Infrared Camera Survey?
I became thoroughly intrigued. A population of large marsupials so close to farms and main highways and yet unknown to science? Who'd have thought it? And in rural Gippsland, of all places. I would find out more about them and, as luck and foresight would have it, I had the means to do so. My robotic cameras can go almost anywhere and they will detect any living creature whose body has an infrared heat signature.
Bobucks' Distribution
How Do We Know?
Possibly the most important question in science, and in life in general, is, "How do we know what we think we know?"
In this case, how do we know these animals are Bobucks and not Common Brushtail Possums?
Here's how ...
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Why Is This Discovery Important?
The broad distribution of these animals in Gippsland is quite surprising because Bobucks' habitat requirements are reported to be more restricted than for their close relatives the Common Brushtail Possums (Kerle, 2001) which have been able to colonise a greater variety of habitats than the Bobuck. For example, Bobucks are not known in urban areas and, until now, have been thought of as tightly adapted to stable environments (Tyndale-Biscoe, 2005). In view of the range of (human) commercial activities that take place there, from farming to extractive industries to land clearing and then re-vegetation, one would hardly think of Gippsland as providing a "stable natural environment".
Although they are reportedly highly dependent upon Silver Wattle A. dealbata (Martin 2005), there appears to be no association of Gippsland Southern Bobucks with any particular type of vegetation: they are to be found in a variety of Eucalypt spp stands or Tea Tree where Acacia spp are absent. Their habitats can be either older growth such as at The Gurdies or, more usually, in comparatively recent re-growth (Koonwarra, Bald Hills). Bobucks are known to feed not only on ground level plants (Kavanagh, 1984; Seebeck et al., 1984; Martin et al., 2004) but also ground level fungi (Seebeck et al., 1984; Claridge and Lindenmayer, 1998; Martin et al., 2004). We suspect this ability, is key to this colonisation of rural Gippsland.
Bobucks are also reported to require tree hollows for denning purposes (Martin 2005). In fact both the ready availability of hollow-bearing trees and Silver Wattle, Acacia dealbata, are held to determine the population density and distribution of Victorian Bobucks (Lindenmayer et al., 1990a). However, suitable hollows appeared to be very few to non-existent at most of the sites surveyed: yet Bobuck numbers seem high in most of coastal Gippsland. Other subjective impressions formed during this survey are that they do seem to require plentiful groundcover, usually in the form of bracken ferns. They also seem to favour locations where a watercourse is nearby.
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Although there are anecdotes and evidence (photographs) of their presence in south west Gippsland for almost the last 30 years, the authors' impression is that they were rare and hard to discover for most of that length of time. For example, biodiversity surveys in the early to mid-90s using spotlights, hair tubes and traps failed to detect them either in or near The Gurdies Reserve. (Kutt and Yugovic 1996, Wilson 1990).
Accepting that these native marsupials were rare or absent for decades past yet are now to be found along the coast from Corner Inlet to Westernport and at points inland means accepting that a substantial yet unobserved population expansion, or more accurately a large-scale colonisation of atypical lowland habitat, has occurred in comparatively recent times. This is a riddle: has such a range extension really occurred? If it has, what might the driving force have been? Was it something something associated with general climate change or rather some purely local alteration in farming or land care practices? This survey was not designed to tell. These are questions that must be left for future work: all we definitely have at the moment is the puzzling fact of their presence.
Habitats of South West Gippsland.
Previous Sightings and History of Bobucks in Gippsland
Amazingly few sightings of Bobucks have been reported from the study area. Apart from three fortuitous photos taken by property owners over a period of more than 30 years, there appears to be no local knowledge of or folklore about these animals at all.
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Bobucks: What's in a Name?
In a recent paper arising from the Survey, the present authors (Hynes & Cleeland) suggested that the name "Southern Bobuck" should replace potentially misleading popular names like "Mountain Brushtail Possum" and others. This would seem less confusing because the Gippsland population, living as they do in a swampy, coastal habitats are hardly "mountain" possums. They can't be called "brushtail possums" because that name is already universally applied to their cousin species Trichosurus vulpecula. Nor is "Black Possum" entirely appropriate because not all members of the population are coloured black.
Why not therefore use "Northern Bobuck" to refer to the northern population, Trichosurus caninus and use "Southern Bobuck" for the the southerners, Trichosurus cunninghami?
Seems logical?
Hynes, D. and Cleeland, M. (2010). Extended range of bobucks Trichosurus cunninghami in south-west Gippsland, Victoria. The Victorian Naturalist, v127(1): 15-19
Many Thanks To ...
- Dr. Jenny Martin: Melbourne University
- Dr. P. Menkhorst: Arthur Rylah Institute
- Department of Sustainability & Environment (DSE)
- Parks Victoria
- Mike Cleeland
- Gary Wallis, Jan Hillyard Anne & Phil Westwood of "Bassbush"
for information about bobuck sightings in Gippsland.
Companies and Products
Endorsed by the Bobuck Survey
The Victorian Naturalist
And, of course, especial thanks to The Victorian Naturalist for taking a scientific interest in my work.
Copyright © 2009 to D. Hynes. All rights reserved.
