19.1a – The Bandicoot

Putting the Q in “Quite strange, actually” (and also in Q fever). (Photo by JJ Harrison)

The bandicoot, besides having one of the best animal names in the world, is an Australian marsupial group with about 20 species. They are creatures that range in size from kind of small to very small, live on the ground, are omnivores, and look sort of like big, energetic shrews. It’s astonishing how much of the mammal world looks sort of like a shrew, really.

The word “bandicoot” essentially means “pig-rat” once you untangle and de-English it. As mentioned before, not only don’t we know exactly where bandicoots fit in the marsupial animal group, but they also have what is essentially a proto-placenta.

One of the things the makes marsupials a completely different type of animal is that they have no placenta. In placental mammals, including us, offspring grow relatively large while still inside the mother, gaining nutrients through the placenta. Marsupial babies are instead born very small and undeveloped, after which they live in the mother’s pouch and gain nutrient from milk.

While the bandicoot is definitely a marsupial, it has a very small and primitive type of placenta. The placental mammals did not develop from marsupials, so this is not some in-between form. Whether it evolved completely on its own by coincidence or whether it was some dormant part of the mammal lineage that in the marsupials only passed down to the bandicoots is uncertain. But there it is.

Some few reptiles and amphibians also form structures similar to a placenta, so it may just be something that is a part of our shared and very distant evolutionary lineage, the sort of thing that in most animals pops up only rarely but became a defining and consistent genetic feature of the placental mammals. In the same sort of way that syndactyly (fused fingers or toes) pops up now and then in animals, but is a consistent feature for kangaroos and their relatives (and also for bandicoots). Placentas are not the norm in the animal world, but the ancestor of all placental mammals happened — perhaps almost randomly — to have this feature, it happened to become a success, and it got passed down to everything from humans to rats to elephants to whales.

But back to bandicoots. Most live in nests that they build in dense or shrubby areas on the ground, or in fallen trees and such. As an ommnivore it eats just about anything, and female bandicoots have been known to even eat their own young when food is scarce. When times get tough it’s every bandicoot for itself, I suppose, but you know things are bad when your children start to look like chicken dinners.

“Come on, Timmy. If you don’t eat your veggies you won’t grow up big and tasty for mama. I mean, strong. Big and strong, right.” (Photo by Bertram Lobert)

Bandicoots live alone except for mothers with young, and though they are timid with other animals they will be quite aggressive and territorial with each other. Many bandicoot populations have decline on mainland Australia because of the invasive foxes and cats, and because of food competition with invasive rabbits.

One type of bandicoot, the northern brown bandicoot, has the shortest gestation period for young of any known mammal in the world. From conception to birth is only twelve and a half days. Yes, I know, every human mother in the audience is now frightfully green with envy, but perhaps you too could get it over with quickly if you were willing to pack the baby around in a pouch on your torso afterward.

Bandicoots are a primary natural storage tank for a bacteria called Coxiella burnetii, which can be passed, via ticks, to livestock. These livestock become infected and the bacteria comes out in their waste products. If a human happens to inhale the smell of these infected waste products, they might get the bacteria as well, and in this manner it can cause Q fever. It only takes one tiny bacteria to infect a human with Q fever.

The Q in Q fever stands for “Query”, because when it was first studied no one knew what caused it. It wasn’t until 1937 that the dastardly little bacteria was found. It can cause flu-like symptoms and pneumonia in humans, or in rare cases can cause hepatitis or chronic (ongoing) inflammation of the heart. As it is very contagious and easily transmitted, the United States has considered its use as a biological weapon. Since only one bacteria is needed to infect someone, it is a highly efficient disease.

Perhaps the bandicoots are getting us back for all those invasive species we introduced.

Bandicoot distribution.

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19 – The Book of Peramelemorphia

A marsupial conundrum. (Photo by Bertram Lobert)

We’ve been on quite a marsupial kick lately, and so I am delighted to tell you that Peramelemorphia is the very last group of marsupials, and once it’s done we’ll have covered them all.

There are two basic types of animal in this group — the bandicoots (about 20 species) and the bilbies (only two). The name of their order means “pouched and badger-shaped”. Pouched they are indeed, but you have to take the “badger-shaped” bit with a grain of taxonomic salt, as is often the case. In reality they look more like a cross between possums and large shrews.

Found in Australia and New Guinea, these animals are essentially the marsupial omnivores, eating anything and everything. What’s interesting about them as a whole is that we don’t have the faintest clue where they came from.

Often when looking at how an animal evolved, scientists look for common features with other groups. There are two main features that bandicoots and bilbies share with some other marsupials that give a strong sense of where they evolved from. The problem is that both of these features point in completely opposite directions.

First, they have several pairs of lower front teeth, which highly suggests that they are related to the marsupial carnivores — the Tasmanian devil, the quolls, etc. And indeed when you look at them you can see how this might be so.

Yet second, and conversely, bilbies and bandicoots all have fused toes in exactly the same manner as the diprotodonts, which is to say, the kangaroos and wallabies, koala and wombat and possums. This is the sort of genetic heritage that is unlikely to have evolved twice, since it formed (probably) to help with tree-climbing and remained even when most of the species took to the ground.

So which is it? We don’t know, but only one can be true, which means the evolution of the the other feature is simply an enormous coincidence. Perhaps the most likely answer is that they evolved from a possum-like creature and evolved extra teeth that just happened to be like those in the mouths of carnivorous marsupials.

But it could also be that the bandicoots and bilbies came first, and that kangaroos and such evolved from them; unlikely but possible. And just as strangely it could be that they evolved from the carnivores and in a staggering coincidence happened to develop the exact same tree-climbing toes as the diprotodonts, but this seems even more implausible.

To make things even worse, bandicoots give birth slightly differently from other marsupials, using something that is almost — but not quite — like a placenta, which is something marsupials in general are not supposed to have.

Confused yet? Science sure is.

Molecular studies solve everything these days, but in this case they have so far failed to shed any light on the problem of where these creatures came from and how they fit into the marsupial tree. When it comes to classification, some animals are outright troublemakers.

16.2a – The Echidna

The Goldilocks of the animal kingdom. (Photo by Laikayiu)

There are four species of echidna in the world, three found only on New Guinea and one found both there and throughout Australia. Along with the platypus they are the only other egg-laying mammals in the world.

They are known as spiny anteaters, but they aren’t related to real anteaters. However they have evolved similar features, including a long snout and an even longer tongue, both perfect for sticking into logs or ant hills to snaffle up a snack.

The “spiny” part of their nickname is accurate enough though. Echidnas are covered in thick spines and coarse hair that serves to protect them from predators. The echidna is generally a slow and non-aggressive beast, so when threatened it simply curls up in a ball, similar to a hedgehog, and waits for whatever is bothering it to go away. It can also swim, using its long nose as a snorkel, and has powerful claws for digging or ripping into food sources.

What it doesn’t have, however, is any sort of tolerance to temperature changes. If it gets too hot, the echidna is incapable of sweating and will avoid the sun for fear of overheating. If it gets too cold, it will enter a torpor to save energy. At both of these extremes, the creature does not enter REM (rapid eye movement) sleep, that deepest form of rest. Like Goldilocks, the echidna wants things juuuust right, and only then (at about 25 degrees Celsius) does it feel at home.

“Too cold. Not coming out.” (Photo by Nachoman-au)

Echidnas do not have particularly good eyesight, but they don’t need it, and even blind echidnas can survive in the wild. To be an echidna you only need to know what the temperature is, how to find some insects, and how to roll into a protective ball. It is helped in this by a weak form of electroreception — not nearly as strong as that possessed by the platypus, but enough to give it a general sense of what’s around it by reading electrical signatures.

One interesting thing about echidnas is that they don’t have normal stomachs. Where other mammals use acidic digestive enzymes to digest food, an echidnas stomach is not very acidic at all. Instead it is made of a very tough material, and the stomach itself clenches and contracts to grind food down into a digestible paste that then passes through the intestine. Its stomach is essentially a second, stronger mouth inside of its body.

This next bit is going to get a little PG, so cover your eyes before you read on. The male echidna is particularly strange because its penis has not one, not two, but four heads. It uses two at a time when it comes to mating, and then switches to the other two for the next time. Handy, one supposes.

All right, you can uncover your eyes now, just in time for one more bit of interesting echidna anatomy. Of all the mammals in the world, the short-beaked echidna has the biggest prefrontal cortex relative to its body size, which is the part of the brain that, in humans at least, is used for planning and analyzing. This has led some scientists to wonder if the echidna might not be an intelligent, reasoning animal. So far, however, tests have shown it to have thinking abilities similar to those of a cat — which isn’t bad, but also isn’t great.

The echidna is the most widespread native Australian animal. You can find it anywhere you go on the entire continent, because as long as there are ants or termites, the echidna can survive.

Echidna distribution.

10.3e – The Tree-Kangaroo

Are they lost, or just very confused? (Photo by Postdif)

There are 12 different types of tree-kangaroos, and they are by far the strangest of the macropods, even if you only consider their evolutionary history.

If you’ll recall, we believe that that the members of Diprotodontia (koalas, wombats, possums, kangaroos, etc.) evolved in trees, which is why their two middle toes are fused together. Eventually some of them came down from the trees and lived on the land instead, including all of the macropods. But then something curious took place. Some of the kangaroos, now living on the land, changed their mind and went back to the trees again.

We think this happened because their ancestors were among the forest-dwelling pademelons (a type of wallaby) that were cut off from all the others by natural forest shrinkage during an ice age. Cut off from other pademelons, they eventually evolved down a different path and returned to the trees, becoming tree-kangaroos.

As you can guess by now, tree-kangaroos are macropods that have adapted for life in the trees. They have completely lost the speed and grace of a kangaroo on the ground; put them on land and they are clumsy and slow, as though they can’t quite figure out what to do with a flat surface. But put them in a tree, and wow.

A tree-kangaroo in a tree is quick and agile, using their strong macropod legs to hop and climb tree trunks and branches like a human with a belt and spiked boots. The animal wraps its arms around the tree limb and shimmies up the tree like an expert. They can also use their powerful jumping powers to literally leap from tree to tree — they can cover a fantastic 30 feet through the air to land in a lower branch in another tree, and can jump down from up to 60 feet up and land on the ground without harm.

Sixty feet? There are superheroes who can’t do that. (Photo by Fred Hsu)

Yes, it’s exactly as weird as it sounds. Essentially they are kangaroos that have started to evolve in the same direction as monkeys. Some of them have even evolved an ability to walk slowly on two legs, because of how their legs are able to rotate in order to allow climbing. They have long tails that help them balance when scrambling along branches. Their hind legs are not quite as enormous as a normal kangaroo’s, but to make up for it their arms are stronger to help them climb.

Most tree-kangaroos live on the island of New Guinea, north of Australia, though some are also found on other small nearby islands and on the extreme northern edge of Australia itself. A handful of tree-kangaroos are endangered, and some others are even critically endangered due to habitat loss and hunting.

But we need to keep them around, and I’ll tell you why. If they’re evolving in a convergent-evolutionary manner in the same direction primates took, how can we resist the urge to give them a few million years and see if they turn out like us? I don’t know about you, but I don’t want to be known as the generation that let the ancestors of a potential race of intelligent kanga-men die off.

7 – The Book of Dasyuromorphia

Hungry marsupials with a hankering for meat. This is a quoll. (Photo by Leonard G)

Dasyuromorphia (pronounced da-see-YUR-oh-MOR-fee-uh) is quite a name, and with seven syllables you know it’s serious, but you won’t be required to remember it for the test. There’s an easier way to remember what they are, because if you had only two words to describe them, those two words are readily available — carnivorous marsupials.

We haven’t looked at marsupials yet, so it’s worth a moment to pause and do so. Marsupials are an older, more primitive form of mammal that give birth to under-developed young. After the young are born, they move into a pouch on the mother’s body, where they can feed and grow larger before venturing out into the world. All baby marsupials are known as joeys, even though the term is commonly used for baby kangaroos. Kangaroos are marsupials, as are koalas, but there are many more than that. There are in fact more than 300 species of marsupials, found in Australia, New Guinea, South America, and a very few in central and North America. Marsupials have developed a lot of different forms, some of which resemble non-marsupial forms because of convergent evolution.

Dasyuromorphia is an order with about 70 species, all of which are meat-eating marsupials found in Australia. There are some carnivorous marsupials found in the Americas, but they were turned away at the door of the Dasyuromorphia Club. Included in this order are a lot of mammals with fantastic names that you’ve probably never heard of, such as quolls, dunnarts, planigales, and the numbat, along with some you have heard of, such as the Tasmanian devil and the extinct thylacine (the Tasmanian tiger). We will soon make certain you have heard of them all! Some of them look sort of like cats, and some look sort of like shrews or mice, but they all have a unique marsupial twist, and they (almost) all have the marsupial pouch with which to carry their joeys.

A few of these animals have some good size to them, but most of them are very small, and because of this many of them are threatened by the plague of invasive species that has swept over Australia in the last century and more, including foxes and cats. You might wonder, how are they carnivores if they are so small? After all, the smallest member of this order is only half the size of a mouse. Shouldn’t a carnivore be big enough to attack things? Well, the trick is that to be a carnivore, you only have to be bigger than something else you can eat. Small carnivores merely need to attack small prey.

It is also worth noting that there used to be several larger marsupial carnivores in Australia, but humans caused all of them to go extinct since our arrival on the island continent 50,000 years ago. The most recent casualty of our presence was the unique and strange thylacine, which was lost entirely by the 1930s. We will still take a look at it, along with all of the other interesting animals in this order.

Dasyuromorphia distribution.