Hello Possums!

I imagine that most of my Australian readers will recognise the allusion in the title, but for anyone else you could search for 'Dame Edna' on your favourite search engine or, perhaps more sensibly, just ignore it! This was to be quite a short post relative to some of my recent ones, partly because I don't have all the photos I'd like for it, and also because the three-part Alphabet of National Parks which began in my last post is something of an odyssey, and we'd probably both appreciate something a bit less substantial. However, a couple of my friends have come to the rescue regarding photos - it's curious that I, who have no artistic bents, have artists among my friends and Kathy Walter and Julian Robinson are among those friends who are much better photographers than I. Kathy in particular is also a mammal aficionado. Their photos are acknowledged as we go; those without acknowledgement are mine. I am very grateful to them for making this a much better post than it would have been.

Before we get to the Australian possums which are the subject of today's post, a quick revision of the origins of marsupials. Perhaps counter-intuitively they seem to have arisen in North America, with the oldest fossil which is definitely that of a marsupial being from Utah and dated at 80 million years ago. From here they spread throughout Eurasia presumably via a land bridge where the Bering Strait now is. It seems that they reached South America about 65 to 55 million years ago, perhaps by the hypothetical Aves Ridge (it exists, but its above-sea history is debated). Here they flourished while elsewhere the rise of the eutherians eventually spelled the fall of the marsupials. From South America marsupials, perhaps just one species, reached Australia via Antarctica about 50 million years ago. 

Big-eared Opossum Didelphis aurita, Trilha dos Tucanos, a lodge in the Atlantic
rainforest inland from Sao Paulo, Brazil. It seems appropriate to offer you a Brazilian 
species here, as it was from here that the American opossums first became known in 
Europe, when Vicente Pinzón presented one to the king and queen of Spain in 1500.

All this is really to say that the numerous American opossums, for which our possums were named, are only very tenuously related. (You will read elsewhere that the Virginia Opossum is the only opossum in North America, but this is untrue - there are eight species in Costa Rica for instance; the previous statement should include 'north of Mexico'.) These species, or their ancestors, moved north from South America when the Isthmus of  Panama rose to join the continents together just three million years ago.

White-eared Opossum Didelphis albiventris, Iguacu Falls, far southern Brazil.
The word 'opossum' is apparently from the Powhatan language of what is now Virginia.

When this officially became 'possum' in Australia is surprisingly unclear. I generally find Edward Morris's 1898 Dictionary of Australian English helpful in such matters but from it I can only deduce that 'opossum' was still the formal term here at that stage, but that 'possum' was being used less formally. Oh well, I don't suppose it matters here!

I suspect that to most eastern Australians at least 'possum' means the Common Brushtail Trichosurus vulpeculus. In fact I was prompted to post on possums by the appearance one morning recently of an adult Brushtail sleeping the day away just outside my study window on the balcony in an uncomfortable-looking site formed by the gap between the heat pump for the house heating and cooling, and the brick dividing wall between us and the neighbours. 

Brushtail Possum sheltering by day on our balcony, presumably because s/he couldn't find
an appropriate hollow (or had been ousted from one). It has now moved on and I hope is
sleeping more comfortably!

Given the short time they've had to adapt to our cities compared to other large urbanites such as raccoons and foxes, I suspect that this may be the best-adapted (or rather fastest-adapted) larger urban mammal in the world. In my experience they are much commoner, or at least easier to see, in cities than in the bush. 

 

But where do possums fit into the world of Australian marsupials? (You can skip this bit without losing the thread if you want, but I'll be brief.) There are some 230 species of marsupial in Australia, New Guinea and nearby islands, and roughly 110 in the Americas. In Australia there are four Orders - the carnivores, the bandicoots, the herbivores (wombats, koala, possums and kangaroos) and the two extraordinary species of 'marsupial mole'. Possums and kangaroos together form a Suborder, also with four groups; the pygmy-possums, the gliders and ringtails, the brushtails and cuscuses - and all the kangaroos! Yep, kangaroos are just the ones who stayed on the ground. It seems that their distant ancestors, the oldest Australian marsupials that we know about, were small carnivores, some of whom took to the trees to access the fruits and flowers up there. In time (at least 35 million years ago), some of them came down again to live on the ground as herbivores and became the ancestors of the wide range of kangaroos, wallabies, potoroos etc.  

Musky Rat-kangaroo Hypsiprymnodon moschatus, Lake Eacham, Atherton Tablelands,
tropical Queensland. This is the smallest and most ancient living kangaroo, and 
perhaps gives us an idea of the ancestral kangaroo.

Those ancient marsupials which stayed in the trees became the ancestors of the modern possums, which form three subgroups (Superfamilies, but let's not go there) of some 70 species. While it's worth remembering that the kangaroos etc are as closely related to the possums as each of the possum sub-groups are to each other, we're otherwise ignoring them today. (But for a lot more about them, see here.)

The largest group, with about 35 species in four families, comprises the gliders and ringtails plus the tiny Western Australian Honey Possum and Feathertail Glider - about half of these are Australian, the rest are from New Guinea and associated islands. Remarkably it seems that gliding, a means of moving between trees without being exposed to the hazards of having to come to ground, has evolved on three separate occasions within this group. Two of the families have both gliding and non-gliding members, while the Feathertail Glider is alone in its family (though it may actually represent two species). There are about 17 species of ringtail, of which six live in Australia. The most familiar of these overall is probably the Common Ringtail Pseudocheirus peregrinus, found all along the eastern seaboard though there is probably more than one species involved here too. It is a much quieter and less pugnacious species than the Brushtail with which it often cohabits in urban situations.

Common Ringtail Possum Pseudocheirus peregrinus, Deua NP, southern NSW.
I unfortunately seem to have missed the characteristic white-tipped short-furred 
prehensile tail here. It has a long bare gripping pad below and acts as
a fifth limb both in climbing and carrying nesting material. They build
characteristic spherical grassy nests, in hollows or foliage, which are
called dreys after similar structures built by squirrels in Britain. In southern Australia
a Common Ringtail is likely to have several dreys in its home range; in the tropics 
it's more likely to use a tree hollow.

 

The Western Ringtail P. occidentalis of south-western Australia is sometimes lumped in with the Common. 

The other ringtail species (in different genera) are all tropical, including three with very small ranges in north-east Queensland rainforests.

Green Ringtail Possum Pseudochirops archeri by the famed and much-visited Curtain Fig
near Yungaburra on the Atherton Tablelands inland from Cairns. It typically hunches like
this to sleep on a branch in the open. Its greenish fur is due to an unusual blend
of white, black and yellow hairs. 

There is also a fascinating rock outcrop specialist ringtail, the Rock (or Rock-haunting) Ringtail Petropseudes dahli from the sandstone country of the Top End of the Northern Territory and the Kimberley. They spend the day sheltering among the rocks but forage at night in trees.

Right among the various ringtail genera is Petauroides, a group of three species of Greater Glider (until recently lumped as one species P. volans). Their gliding membrane stretches from the elbow to the 'shin' (or tibia) and with it they can cover distances of 100 metres, making turns of up to 90 degrees and flattening at the last moment to hit the trunk of the target tree vertically. Because of this attachment it doesn't spread its arms out while gliding but sticks out its elbows and tucks its paws under the chin.

Southern Greater Glider P. volans, Boonoo Boonoo NP, north-eastern NSW. A truly
beautiful mammal, one of only two (along with the Koala) to live almost solely on
eucalypt leaves - an awful diet but a guaranteed one. Unlike most other possums they are
almost entirely silent. The colour is very varied and near-white individuals are common.
Photo courtesy Kathy Walter.

A second family within this grouping comprises most of the rest of the gliders - the 'wrist-winged' gliders - and the enigmatic and striking tropical Striped Possum.

Striped Possum Dactylopsila trivirgata, Lake Eacham, Atherton Tableland,
tropical Queensland. This is probably the most visually spectacular of possums;
this one, plus three other species, are also found in New Guinea. This lodge on
the edge of Crater Lakes NP attracts these and Sugar Gliders in the evenings by
applying honey to the trunks in front of a small 'grandstand'. This would normally
make me very uncomfortable but the animals are clearly not dependent on the
offerings; some nights they don't come at all and they don't come at predictable times.
Moreover, the Striped Possum is largely carnivorous.

This fuzzy blow-up features the greatly elongated fourth toe which is critical to its
foraging for wood-boring beetle larvae, an important food source. Its two adze-like
lower incisors chew away the wood and bark, and the toe (or its long tongue)
hooks out the wriggling snack. This is probably the least-known of Australian possums,
though it is not uncommon in its tropical forests and woodlands.

Until recently there were four species of the 'wrist-wings' in the genus Petaurus, but now the (relatively) familiar and very widespread Sugar Glider (P. breviceps) has been split into three - and it seems that further work in the tropics may reveal even more species. The true Sugar Glider seems now to occur only to the east of Great Dividing Range; the animals west of the range (including around Canberra) are Krefft's Gliders P. notatus and the tropical savanna populations are of Savanna Glider P. ariel. My previous neighbours in inner northern Canberra had a family of Krefft's Gliders living in their roof cavity! I haven't tried to illustrate all three, as they are physically very similar.  As the group name implies they have a full gliding membrane attached at wrists and ankle and are very adept aerialists. They are small, with a body less than 20cm long and the tail about the same length again.

Krefft's Glider (almost certainly) at the feeding station at Lake Eacham. Unlike the Striped
Possums with which they sometimes feed here, nectar and other plant exudates feature in
their natural diets. They roost in hollows in family groups of half a dozen adults plus
young, and emerge together to forage. The edge of the non-extended gliding membrane
can be seen in the photo.

Other members of the genus are larger. The Squirrel Glider P. norfolcensis is a woodland species of about twice the bulk. In the south-east it is only found west of the Great Divide, but further north it comes to the coast. 

Squirrel Glider, Chiltern forest, Chiltern-Mt Pilot National Park, northern Victoria.
The very bushy tail, especially at the base, is a good identification distinction 
from the sugar gliders. 
Photo courtesy Julian Robinson.

The highly endangered Mahogany Glider P. gracilis is noticeably larger again; it is limited to a very small section of coast in the Wet Tropics of Queensland between Ingham and Tully. It was only recognised as a separate species in 1993, having been 'lost' for a century since its initial description as a separate species, which was soon after rescinded. By this time much of its habitat had disappeared, especially to the sugar cane industry.

The largest by far though of these gliders is the spectacularly active and noisy Yellow-bellied Glider P. australis. They are found along much of the east coast and hinterland and, while threatened by logging, they are still reasonably common in the south, but the tropical populations (represented by the one below) are in danger. 

Yellow-bellied Glider, Atherton Tablelands; the alert posture in typical. Its attention-
grabbing shrieks are said to be audible half a kilometre away. 
I once heard one glide past my tent in the Brindabella Ranges, with a truly
alarming gurgling wail; I have since heard that this call is only uttered 
while gliding (and is uttered during most glides) so probably has 
a function in the coordination of group movements. 
Like other wrist-wing gliders it chews holes in tree trunks to lap the sap flow.
Photo courtesy Kathy Walter.

The highly endangered Leadbeater's Possum Gymnobelideus leadbeateri of the montane ash forests of Victoria near Melbourne is in the same family and is like a sugar glider without the gliding facility.

 

Two other very small families (in species numbers and individual size) complete this group. The tiny Honey Possum or Noolbenger Tarsipes rostratus of south-western Australia is less than 20cm long including the tail and weighs less than 15g. It is entirely reliant on nectar and pollen and is an important pollinator of plant groups such as banksias. It is the only member of its family. The three remarkable photos that follow were all provided by Julian Robinson and were taken at Cheynes Beach near Albany.

 

Honey Possum with its nose deeply embedded in the banksia flower spike.

Honey Possum licking nectar from the banksia flower, its tongue clearly visible.

Honey Possum with banksia pollen on its whiskers (you may have to click
on the photo to see it properly).

The final family in this grouping comprises just two species of equally tiny possums, though only one is found in Australia. The Feathertail Glider Acrobates pygmaeus is found from the south-east coast to the tip of Cape York Peninsula though its size (think a small mouse) means that it isn't often seen. (There is actually a good argument for two Australian species being involved, though that's not yet been generally adopted.) The relatively thick gliding membrane is attached to elbows and knees, and the eponymous feathery fringed tail doubtless assists in the glide too. It has insect-eating teeth and a brush-tipped pollinator's tongue. 

Feathertail Glider Acrobates pygmaeus Beowa NP, far south coast NSW. 
This is the world's smallest gliding mammal. I have spent time in the same campground 
without seeing this little beauty - note to self, be more assiduous! 
Another remarkable photo. Photo courtesy Kathy Walter.

The second group of Australian possums comprises larger animals, the brushtail possums, cuscuses and the Scaly-tailed Possum.

 

The brushtails, as I mentioned earlier, are doubtless the possum that most Australians will think of, because one species, the Common Brushtail Trichosurus vulpeculus, is found across most of the continent, though it's now very rare in the arid lands and declining in the north and south-west. However it is still an abundant urban animal in the east, and is likely to be found scrounging in most park campgrounds. Atypically among possums, the brushtails inexplicably lack the powerful gripping structure of the front feet, where the first two toes oppose the other three.

 

Common Brushtail investigating the bird feeder at night in my former Canberra 
back yard. I had three or four living in my garage most of the time and except in 
drought time they foraged away from home and mostly left my vegie garden alone.
When the Millennial Drought was at its peak though they even ate the bark off
my chilli plants; I gave up at that point. They are mostly vegetarian and eat a lot
of leaves - including some that are toxic to most animals - and fruit and flowers.
They are big animals, up to three kilograms, so need a lot of food.

While they 'normally' spend the day in tree hollows, there are simply not enough
such hollows to support the large urban populations, and like the one on our
balcony that I mentioned earlier, will make do where they can. This mother and
baby had settled into the one of the bird hides at Canberra's Jerrabomberra Wetlands.

There has long been also recognised a closely related species of the ranges, the Mountain Brushtail or Bobuck T. caninus. However in 2002 it was realised that this comprised two species, roughly north and south of Newcastle in hinterland forests; the new species, T. cunninghamii, referred to the southern animals and retained the Mountain Brushtail (or Bobuck) name (though the subsequent discovery of Victorian populations in eastern lowlands was unfortunate in this regard!). T. caninus in the north became Short-eared Brushtail (or Bobuck). Confused? Never mind, here's one to take your mind off the names! 

Short-eared Brushtail, Chichester State Forest, south of the Barrington Tops in NSW.
This one was very much at home in the campground.

In addition the isolated and distinctive coppery race of the Atherton Tablelands, and the not-very-brushy-tailed brushtails of the Top End are also considered by some to be separate species, which may well be accepted in time.

The most numerous possums within this group are the 22 species of cuscus, most of which are in New Guinea and nearby islands, though two of them are also found in tropical far north Queensland. They have distinctive short faces and long prehensile tails, and are mostly vegetarian though at least some also take eggs and small animals opportunistically. They are hard to see in the rainforest canopy and roost well-hidden during the day. 

Waigeou Cuscus Spilocuscus papuensis, West Papua, Indonesia.
This species is closely related to and very similar to the Common Spotted Cuscus
S. maculatus, found on Cape York.
 Photo courtesy Kathy Walter.

Lastly in this group is something of an outlier, the rock-specialising Scaly-tailed possum Wyulda squamicaudata of the remote and rugged Kimberley region of far north-western Australia. 

Scaly-tailed Possum at Bachsten Camp, Kimberley.
During the day they rest in rock piles and crevices such as this, and 
forage for plant material at night, mostly in trees.
Photo courtesy Kathy Walter.

Finally the third group of possums comprises just five species of tiny pygmy possums (though some would include them in the previous group). They are mouse-sized, with long prehensile tails and occupy habitats from heathlands to wet forests and tropical rainforests, and to alpine boulder fields in the case of the Mountain Pygmy-possum, Burramys parvus. This one has a total, non-continuous range of only some 600 hectares in the Australian Alps, so is at extreme risk from climate change - once you've been driven by rising temperatures to the top of the mountain there's nowhere else to go. The other four are not regarded as nearly so precarious. They are mostly insectivores though some take nectar and the Mountain Pygmy-possum eats hard seeds. 

The story of the discovery of the Mountain Pygmy-possum deserves retelling. In 1966 a strange mouse-like animal with a prehensile tail was captured in the University ski lodge at Mt Higinbotham in the Victorian Alps. Back in Melbourne it was held at the Fisheries and Wildlife Department and examined by Norman Wakefield, a scientist and pioneer biology communicator who’d actually been working on Burramys fossils that he’d recently found in East Gippsland. He looked at the teeth and immediately recognised the living animal from the fossil. The following telegram was sent to mammal doyen David Ride in Perth. "BURRAMYS EXTANT STOP NOT REPEAT NOT EXTINCT STOP LIVE MALE CAPTURED MOUNT HOTHAM STOP AM TRYING FOR FEMALE."

Later in his book Guide to the Native Mammals of Australia, Ride wrote with passion and allusion of his reaction to that telegram. “Burramys had come to life. The dream dreamed by every professional palaeontologist had come true. The dry bones of the fossil had come together and were covered with sinews, flesh and skin. Burramys lived”. This seems to me a wonderful and wholly appropriate expression of joy from a senior, and sometimes dour, scientist.

Eastern Pygmy-Possum Cercatetus nanus, Beowa NP, above and below. This one is
somewhat atypical in mostly eating nectar and pollen, and is known to be a significant
pollinator of banksias and waratahs. 
Photos courtesy Kathy Walter.

This post has turned into a longer journey than I'd planned (as is often the case I find!) but I hope you've enjoyed the ride and found something of interest and pleasure along the way. And I hope you love our possums as much as I do!

NEXT POSTING THURSDAY 6 NOVEMBER

I love to receive your comments and in future will be notifying you personally by email when a new posting appears, if you'd like me to. All current subscribers have been added to this mailing list and have already been contacted. This will mean one email every three weeks at the current rate of posting. I promise never to use the list for any other purpose and will never share it.
Should you wish to be added to it, just send me an email at calochilus51@internode.on.net. You can ask to be removed from the list at any time,or could simply mark an email as Spam, so you won't see future ones.
If you do leave a comment - and I love it when you do - please remember to click the
box below your comment that says 'Email follow-up comments to...[your address]'
so you'll know when I reply - and I always do!