10.2e – Leadbeater’s Possum

A tragedy in the trees. (Photo by Pengo)

In the southeastern corner of Australia live perhaps the oldest and rarest of all possums, Leadbeater’s possum. They aren’t named for their ability to work with metals, but rather after an Australian taxidermist named John Leadbeater.

Their story begins in the years between 1867 and 1909, when science learned of this possum through only five specimens collected during that 40-year period. What they learned was that Leadbeater’s possum was a primitive, ancient type of possum that had survived down through the years while others had changed or gone extinct.

A nocturnal creature, the possum lives in family groups of up to 24 animals that nest together in the hollows of trees. However, hollows only form in very old trees, and in order to survive they also needed a constant supply of food. These restrictions kept the old possum species living in a very small area in the old growth forests of southeast Australia.

After 1909 scientists stopped being able to find even the occasional Leadbeater’s possum, and the scientific community figured that the poor old fellows had finally shuffled off to the great tree hollow in the sky.

But in 1961 a Leadbeater’s possum was discovered again, and in 1965 we finally found a whole small colony of them living together. More searches uncovered their whole population range, a small and specific area of the old growth forest where everything was like Baby Bear’s bed for Goldilocks — juuuuuust right.

The problem was that the possums needed trees of a very specific age to live in, and good supplies of fresh greenery to eat. We believe that in the past, the possums always moved on to a new area when the old area got too old. With humans logging much of the forests, the number of new areas to move to has grown steadily fewer as time goes by.

There were about 7500 Leadbeater’s possums by the 1980s, when they were living in an area that had been swept by fires in 1939 — there was good young regrowth and there were old dead trees to live in. But by 2009 they had declined to about 2000 possums as their forest was getting too old and they couldn’t really move anywhere else. That’s when the worst possible thing happened.

In February of 2009 the Black Saturday fires, a series of devastating bush fires in Australia, completely destroyed most of the possum’s remaining habitat, and most of the possums themselves in the process. By the time the smoke cleared, this already-endangered species had only about 100 remaining members.

Combined with continued logging in the region, this means that the possum’s only hope for survival rests in the hands of mankind. Efforts have been made to protect the possum’s area from any logging, but counter-efforts are trying to allow logging regardless of the presence of a critically endangered species. A handful of Leadbeater’s possums have been taken into captivity, but they have proven difficult to breed, though efforts are now being met with some success. But the truth is that there aren’t many left, and even those low numbers are falling. Our efforts may be too late.

10.2d – The Brushtail Possum

The roly poly possums and their pesky kids. (Photo by Bryce McQuillan)

Some of the best known possums are the brushtail possums, and particularly the common brushtail possum, which is found in most of the country’s coastal areas and in nearly all of its major cities. In fact it is the most widespread mammal on the continent.

The common brushtail possum is the biggest of all possums, about two feet long with a big bushy tail that stretches another foot or longer. Because this bushy tail is prehensile and used for grabbing branches, it has no hair on the underside, as hair would get in the way of gripping. This makes sense when you think about it — on surfaces meant for gripping, such as the palms of hands and the pads of feet, animals don’t have hair, and even the hairiest human grows nothing on the soles of his feet or the palms of his hands.

Though common brushtails live in in the wild, many of them have easily adapted to life in human cities as well, making them in some ways the raccoons of Australia. They are clever and can easily survive by stealing from fruit trees and gardens or even breaking into houses and going through any food left out on the counters. They are utterly omnivorous, and will eat both plant matter, insects, and even small mammals and birds. They will sometimes take up residence in attics and they make a lot of different sounds, which can bring the Australian night alive in the same manner as monkeys in the jungle might do.

Common brushtails have some interesting social habits. Like humans, they don’t have a mating season and can breed at any time, but to make up for this there are other rules that the males have to follow. In one population it has been observed that a male had to spend time with a female for at least a month before she would agree to mate, which is possum years is practically forever.

There is also a big social difference between having sons and having daughters in the possum world. Male common brushtails will go far away to establish their territory after they grow up, but females will stick close to their mother’s territory, and will grow up to compete with their mother for nesting sites and dens. Because of this, in areas where there aren’t enough nesting sites, common brushtails will give birth to more males than females so that there is less competition in the future. How this mechanism works is uncertain, but gender selection for joeys does not appear to be entirely random. When there are lots of nesting sites, more females are born to help fill them all up.

The moral of the story: it’s a weird, possumy world down under.

10.2c – The Gliding Possums

Up, up, and away! This feathertail glider is the smallest of the gliding possums, and the cutest of the gliding anythings. (Photo by Doug Beckers)

There are a number of gliding possums, such as the tiny feathertail glider pictured above, but the best-known of them is the sugar glider, a marsupial found in east and north Australia that measures about a foot from head to tail. Gliding has evolved several times in the mammal world, each time separately in creatures that are only very distantly related.

Sugar gliders are well-known because they can be easily domesticated, and are legal to keep as pets in most (but not all) places. Most pet sugar gliders are bred to be pets, but some are taken illegally from their natural habitat and sold to pet owners.

The sugar glider looks sort of like a squirrel, with a longer tail that is prehensile enough to grip branches. It’s a nocturnal animal that snacks on small animals and also on sweet tree sap, which is what puts the sugar in a sugar glider.

And what puts the glider in a sugar glider is of course the membrane of skin that stretches between the back legs and the front legs, called a patagium. With this the sugar glider can sail through the air for distances of 150 to 450 feet. Even the little feathertail glider can go 75 feet through the air. In this astonishing manner they soar from tree to tree in the darkness.

For the sugar glider, it ain't nothing but a thing. (Photo by Anke Meyring)

As though the evolution of gliding wasn’t improbable enough, it seems as though gliding has evolved in the possum group more than once. There are quite a few gliding possums, some more related to one another than others, and one, the greater glider of east Australia, doesn’t appear to be very closely related to the other gliding possums at all. Instead it is a type of ringtail possum that happens to have developed gliding all on its own. Perhaps it’s simply something that develops sometimes among tree-dwelling species. After all, if you fall out of trees sometimes, evolving a gliding membrane is pretty handy, and it’s only a small step from there to becoming the possum equivalent of Batman.

The greater glider is much bigger than the sugar glider. Just its body is more than a foot long, and it has a ridiculously long tail that measures nearly two feet beyond that. It also glides differently than the other gliding possums. The others throw their arms wide and have a patagium that fills all the space between their wrists and ankles, and they glide like a person pretending to be an airplane with their arms spread wide and maybe making motor noises with their mouth. The greater glider’s patagium only runs from its elbows to its ankles, making it vaguely triangular-shaped. The animal tucks its wrists under its jaw when it glides, and controls its movement by tilting its elbows.

Some gliding possums are endangered because of habitat loss, but others are doing all right, having adapted. They are vulnerable to predators on the ground, where they are typically slow and clumsy, meaning that areas where trees are too far apart to glide to are like buffet tables for invasive cats and foxes.

10.2b – The Honey Possum

Honey, I shrunk the possum. (Image by John Gould)

The honey possum is an itty-bitty opossum found in extreme western Australia, which weighs only about half as much as your average mouse. It is not closely related to any other possum, but that’s not what makes it strange. What makes it strange is that the honey possum is one of the only mammals, along with some bats, that is a nectavore.

A nectavore is an animal that survives mostly through eating nectar from flowers, though some nectavores are also insectivores. A nectavore is typically doing the flower a favour — the nectar is a sweet treat to tempt the animal in to feed, and in return the animal accidentally gets pollen on its feet or body, which it transfers to other flowers and so helps the flowers reproduce.

The honey possum is one of those animals that lives entirely off nectar. Because these possums are very small and cannot fly like many other nectar-eaters, they need lots of flowers in a small area in order to survive. As a result, they are quite common in their particular corner of Australia but cannot really venture any further as a species, since most of the continent is dry and spread-out.

In order to get at nectar, the honey possum has a long nose and an even longer tongue, and the tip of its tongue is bristled to help gather more nectar. It is essentially the mammal equivalent of a flightless hummingbird.

Because of competition for females during breeding season, male honey possums have the largest testes relative to body weight of any mammal in the world — the exact figure is 4.2 percent of body weight. Their sperm is also the largest of any mammal’s. So when it comes to questions of masculinity, you must ask yourself: are you a man, or are you a honey possum?

10.2a – The Possums

"Im-possum — oh, you did that pun already with the opossums. Well, fine. I see how it is." (Photo by JJ Harrison)

The most important thing to know about possums is that they are completely different from opossums. Both are marsupials, but they are not closely related, and they are very different animals. They don’t play dead like opossums do. They don’t scavenge like opossums do. They don’t live in the Americas like opossums do. Even though Americans refer to opossums as “possums”, when Australians say “possum” they mean something completely different. Which is pretty much par for the course when it comes to things Australians say, come to think of it.

Possums are part of the same order as koalas and kangaroos, and they are basically the big, chubby squirrels of Australia. Not all of them are big (the little pygmy possum is only three inches long), but most of them are bigger than squirrels, at any rate. They have long, sometimes bushy tails, and there are about 70 different species of possum.

There are a few different basic types of possums, plus a few that don’t really fit the common definitions. There are the small pygmy possums, which have prehensile tails and are sort of like mice, if mice climbed trees and could jump great distances. There are the brushtail possums, such as the mother and joey pictured above, which have big bushy tails, and there are the cuscuses, which are sometimes-strange possums that live scattered across New Guinea and various Indonesian islands.

There are the ringtail possums, which are essentially bigger versions of the pygmy possums. There are the gliding possums, which can glide through the air like a flying squirrel. One of the gliding possums is as small as a mouse, which makes for an adorable image when you think about it soaring through the air with its arms outstretched. And then there is the honey possum, which is the weird cousin of the group. Every family has one. If you don’t think your family has one, it’s probably you.

And if you spend your nights climbing utility poles like this ringtail possum, it's definitely you. (Photo by Superflewis)

Possums provide an interesting example of how, even though Australia is plagued with invasive species, it can still inflict that same ecological curse upon other places. European settlers in New Zealand wanted to start a fur industry there, and so they imported large numbers of brushtail possums from Australia. Since there are no natural predators on New Zealand that are willing to eat a possum, their population exploded to the point where there were 70 million possums in New Zealand, which is not an enormous country. The possums damaged trees and wildlife, and spread disease to native species. New Zealanders went nuts trying to trap and kill possums, producing countless articles of clothing labelled as eco-possum or possum wool clothes, marketed, strangely enough, as an ecologically friendly type of fur, since killing the possums was helping the natural island habitat. Today it is estimated that possum numbers in New Zealand have been reduced to a mere 30 million. Still a few coats to go, I guess.