Australian mammals - monotremes, marsupials and placentals

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Mammals of Australia 

Australian Aboriginals had been accustomed to them for millenia,
but early white explorers were amazed by what they found in Australia,
and even today we are uncovering more and more remarkable facts about our mammals

What is so odd about Australian mammals?

whiptail wallaby
  • Australia is the only continent (and one of the only two countries - the other being New Guinea) in the world to still have all three of the major groups of mammals: monotremes, marsupials and placentals
  • Half of Australia's mammal species are marsupials (South America has a few dozen species - all in the opossum family - and a couple of species have found their way into North America, but Australia is the only continent to have such a diverse range or to have marsupials as their most common and conspicuous land mammals)
  • It is the only country in the world to have platypus, kangaroos (although New Guinea and some neighbouring islands do have wallabies), koalas, wombats, marsupial "moles" and numbats
  • It is the only continent other than Antarctica to not have native hoofed animals, or terrestrial native Carnivora (dogs, bears, cats, weasels etc., but we do have seals and sealions) - the dingo appears to have arrived from Southeast Asia only about 4,000 years ago, probably with Indonesian traders. It is also the only continent to have rainforests but no monkeys
  • Not only do we have mobs of great, two-legged hopping herbivores taking the place of deer and cattle, but we have a strange little furry creature that swims, lays eggs, give milk to its young, has a venomous spur, and uses electricity to find its prey, also small predators that revel in mating encounters only to have all males die of stress-related conditions within three weeks, a spiny but furry animal that develops a pouch shortly before laying an egg  .... and much more

koala

The world's three great groups of mammals: monotremes, marsupials and placentals are all found in Australia

The evolutionary relationships between this groups is not yet completely understood.

Further references

What is a mammal anyway?

The short answer is a vertebrate that gives milk to its young.

A more detailed response is that a mammal:

Monotremes

platyp[usMonotremes lay eggs but give milk to their young, are covered in fur, and share other characteristics of marsupial and placental mammals.  Their body temperature is lower, and they can when need arises allow it to drop considerably to slow down metabolism. Their locomotion has reptilian qualities, and the adults have no teeth. The name means one opening, which refers to the cloaca (similar to that of birds and reptiles) through which the eggs are laid as well as waste products being eliminated.

 Platypus are found only in Australia, but we share echidna with New Guinea ( three species over there, including our species).

The first platypus skin to be taken to England was simply not believed - skeptics were convinced it was the work of a skilled taxidermist stitching various other animal parts together. And that was only because of its bizarre appearance.  No one yet knew that this furry, milk-giving animal also laid eggs (that discovery was to cause further furore, although Aboriginals had long known this fact), that the male had a venomous spur (making it the only known venomous mammal in the world), that they have the highest rate of REM sleep of any mammal, or that they seek their prey not by sight but by using their rubbery bill which is sensitive to electrical and other vibrations from the muscles of aquatic crustaceans, insects and other small creatures. The white you see around the eyes when they forage are small patches of white fur - the eyes are closed while diving and pursuing prey.

echidnaThe echidna, though often mistakenly called a porcupine or thought of as an aberrant hedgehog, is no less strange.  It also lays eggs although furry and milk-giving, and the female develops a pouch while pregnant - the young live there until they become too prickly! The long rubbery bill is a similar substance to that of the platypus bill, and is used in procuring ants and termites from their nests. There is just one species in Australia, found also   in New Guinea along with a further one to three species, depending which taxonomy is accepted (most commonly accepted nowadays seems to be dividing the long-beaked echdina into thee species - western, eastern and Attenborough's (or Sir David's)). Males (which incidentally have a strange, four-pronged penis) may sometimes be seen in  the breeding season (winter) forming a 'love-train' in pursuit of a female, and soon both sexes start digging small trenches to facilitate mating.

That  then is the sum total of all living monotremes - but what amazing creatures they are!

Steropodon galmani was a monotreme that lived amongst the dinosaurs in the early Creatceous, suggesting the group evolved within the Australian section of Gondwana in the Jurassic - they have certainly been in Australia a long time! There have also been fossilized platypus (different species to today's) found in Argentina - not surprising as Australia, Antarctica and Australia were still joined during the Cretaceous. They may have also had relatives in Madagascar, but fossil records are scarce and this hypothesis does not seem to currently hold much favour. It is thought that the echidna lineage evolved in Australia  from platypus-like ancestry.


Marsupials

Marsupial young are born t a very elementary stage of development.  This seems a but hard on Junior, but it's good for Mum - no long and heavy pregnancy. The tiny newborn - with mouth and arms well-developed but not much else - must climb all the way to the nipple and attach for the next few weeks. There are also skeletal differences that are used to distinguish marsupial fossils from placentals

Four orders of marsupial are now generally recognized in Australia and another two in South and Central America (opossums - one of which has reached North America - and shrew-opossums)

The four orders of Australian marsupials are:

Carnivorous marsupials: (Dasyuromorphia)

dunnart
Tasmanian devils, quolls, dunnarts (the mouse-sized predator pictured to the right) and other members of family Dasyuridae have many sharp teeth on both upper and lower jaws, and relatively simple feet (compared with herbivorous marsupials). Most species are  rat-sized or smaller and all are nocturnal, so most Australian residents do not even notice their existence, except that ion some country areas the mouse-sized  antechinuses enter houses in search of insects or winter warmth, and the larger phascogales (squirrel-size) or quolls (large cat-size) occasionally help themselves to chickens. The introduced cane toad is a serious threat to these larger species.
The smaller members of the family go into a kind of frenzy of fighting (males) and mating in early spring, the couple staying physically coupled and active for several hours, then within the month all males die of stress-related disorders while the female lives on to raise her brood.

The numbat has similar feet and basically similar dental structure but with highly reduced teeth due to specialization for its diet of ants and termites.This attractive, alert  and delightful little animal is sufficiently different to have a family of its own, and is now regrettably endangered, and confined to the southwest corner of Australia

The wolf-like thylacine was also sufficiently different to have a family of its own.  According to the fossil record there were several species, just one remaining by the time Aboriginals arrived in Australia.  After the dingo arrived (probably brought in by Indonesian traders around 3000 years ago) the thylacine became extinct on the mainland, but was still going strong in Tasmania, until white settlers arrived and found it was eating their chickens and sheep. By the time legislation was passed to protect it, it was too late, and the last known individual, Benjamin, died in captivity in 1936,  on September 7th, a day that is now remembered each year as Threatened Species Day.

northern brown bandicootBandicoots and Bilbies (Peramelemorphia)

This order appears to be half-way between the carnivorous and herbivorous groups in two ways:
Some bandicoot species are common, even appearing in suburban backyards, but others are threatened, by habitat loss, competition with rabbits, and predation by foxes and cats

There were two species of the strange, rabbit-eared bilbies.  The lesser bilby has not been seen since the 1960's and is probably extinct, but the greater bilby, while till endangered, is now the subject of some very active campaigns to protect it.

Herbivorous marsupials (Diprotodontia)

This group is united by the following features: This herbivorous order includes:

Kangaroos, wallabies and pademelonseastern grey kangaroo

There is no sharp zoological division between kangaroos and wallabies. The three largest species were called kangaroos and most of the others are called wallabies regardless of how closely related they are to the species known as kangaroos.

The red kangaroo is very wide ranging in inland areas, from woodlands through to deserts

The eastern grey kangaroo (pictured)  is the only kangaroo seen on the east coast (and the only one in Tasmania), but is also found as far west as southeastern South Australia in the outback

The western grey kangaroo is found from Australia's southwest coast through to western Queensland, western Victoria and western New South Wales, their range thus overlapping with the eastern grey. They are darker and browner in colour than the eastern grey.

Next in size to the kangaroos but still in the same genus (Macropus, meaning 'big foot') are two species of wallaroo (as though someone couldn't decide whether to call them kangaroos or wallabies) and the euro.

red-necked wallabySeveral wallabies are also in the same genus, and would have been called kangaroos if they had been big enough (thus there is no sharp scientific division between the terms 'kangaroo' and 'wallaby.' Pictured to the right is a red-necked wallaby, in the genus Macropus.

brush-tailed rock-wallabyThere are several other wallabies belonging to separate genera, such as the swamp wallaby, the nail-tailed wallabies, the hare-wallabies and the rock-wallabies (pictured to the left is the brush-tailed rock-wallaby).

Tree kangaroos are true members of the kangaroo family (but not in the kangaroo genus) that have adapted to life in the trees in the rainforests of far north Queensland and New Guinea. There used to be more species in Australia in the geological past when rainforests were more extensive, and nowadays we have have only two, while several species still occur in New Guinea. They hop like 'normal' kangaroos along the branches and on the ground.

Pademelons are small wallabies of the east coast living in dense forests that would impede the leaping ability of some of the larger species.

Quokkas are wallabies from the southwest of Australia, nowadays mostly on Rottnest Island near Perth

Conservation note:

A number of species of small wallaby are now threatened because of habitat destruction and feral predators (the kangaroos and larger wallabies are locally threatened in some areas but the species are nowhere near as endangered as some of these smaller wallabies).

 

Potoroos, bettongs and rat-kangaroos

These are small relatives of kangaroos and wallabies, possibly a similar size to the early kangaroo ancestors about 15 million years ago.

The musky rat kangaroo is one of the few marsupials active during daylight hours, and is found in the tropical rainforests of far north Queensland, where it is an important disperser of seeds. They have prehensile tails, with which they carry foods and nesting material. The desert rat-kangaroo (not closely related to the musky) was by contrast an animal of extreme aridlands of the outback but is now probably extinct.

Potoroos (see photo to left) are found in rainforests and eucalypt forests, and are important dispersers of miccorhyzal fungi (fungi which live in a symbiotic relationship with roots of forest trees: they process certain minerals in such a way as to make them much easier for the roots to absorb, and in turn get structural support from the roots). There were three species but now only two.

There are several species of bettongs (some endangered), collectively found throughout Australia but each restricted to particular habitats
 

Possums and glidersbobuck


There are four "super-families" of diprotodont marsupials collectively containing the families of animals we collectively call possums (none of which resemble the opossums of the Americas - a totally different group of marsupials) :

    * Pygmy possums (Burramyoidea)
    * Ringtail possums, striped possum, Leadbeaters possum and several gliding possums (Petauroidea)
    * Brushtail possums, cuscuses and scaly-tailed possum (Phalangeroidea)
    * Honey possum and feather-tailed glider (Tarsipedoidea: some dispute the close relationship of these species)



 

Wombats


There are three species of wombat - the common wombat found in southeastern Australia including Tasmania, and two much rarer species, the southern hairy-nosed wombat of outback South Australia and the highly-endangered northern hairy-nosed wombat of outback Queensland (which used to also be found in parts of New South Wales but is now extinct there). They are powerful burrowers, and live mainly on grasses. An oddity is their droppings, which are cubic - this appears to be so that a wombat can leave a deposit to mark his territory on new objects that appear within it - a deposit that will not roll off as readily as a round one would.

koalaKoala


The closest living relatives of the koala are the wombats (turn a wombat 90 degrees, put it in a tree and give it fluffy ears and it would almost look like one). It is unusual for a tree-climbing animal to lack a tail, so it seems probable that the ancestors of both were ground-dwelling animals, and the koala secondarily moved back into the trees. In the geological past there were several species of koala, but there is now only one, although there are a few different races.

They have a very restrictive diet, eating only the leaves of Eucalyptus and Corymbia species (Corymbia are so similar to Eucalyptus that until recent years they were include in the same genus), and not just any species even of these. Eucalypt leaves are difficult to get all one's nourishment from - they have low levels of nitrogen, they have many indigestible chemicals, and only the young leaves are tender. There are only a couple of dozen species koalas regularly eat, and in any particular area within Australia there are usually less than half a dozen species the koalas will eat.


Marsupial "mole" (Notoryctemorphia)

This odd little animal is sufficiently different from other marsupials to have a whole taxonomic order to itself. It looks remarkably like the golden mole of Africa, and behaves in a somewhat similar way, but they are not at all closely related: they just have very similar lifestyles and have adapted in similar ways (but of course the golden mole is a placental, its young are thus born at a more advanced stage and they are not kept in a pouch). The marsupial 'mole' (since we don't yet seem to have a better common name for it) has a beautiful golden coat but is seldom seen, as it spends most of its time underground in remote areas of the outback.


Placentals

Australia has NO native placental carnivores (i.e. cats, dogs, bears, raccoons etc - the dingo, now known as "Australia's wild dog", was introduced about 3000 years ago), NO native hoofed animals (deer, goats etc.) NO primates (monkeys and apes) and indeed NO native placentals except those listed below

The native placentals we DO have are:

little red flying fox

fruitbats in flightBats

Because they could fly, bats reached Australia quite early - at least  50 million years ago, and about a quarter of all native Australian mammal species are bats. Bats belong to two sub orders which are similar in having their fingers greatly extended and modified for flight but differ in some important ways:

Megabats

These include the flying foxes (fruitbats:pictured above), the blossom bats and the tube-nosed bats, found in northern and eastern Australia. Because they do not echolocate they do not need the elaborate nose-leaves and large ears the microbats usually have, but instead have more typically mammalian faces, leading to the common names 'flying fox' in English and 'flughund' in German. Their diet consists of fruit and nectar, some species favouring one more than the other.

Microbats

There are six families in Australia, and although some species are rare, collectively the microbats are very common throughout Australia, often a dozen or more species being found in any one locality. They are not, however, 'interchangeable.' Some prefer more open habitats to others, some forage above the canopy and others below, some catching insects from the water, some eating small vertebrates as well as insects, some able to keep hunting during winter while others can't, etc. Some sleep in caves, others in vegetation or old bird nests.

Rodents

About a quarter of all native Australian mammal species are rodents (which comes as a surprise to many suburban Australians who usually only see the introduced rodent species). Three of the world has a higher proportion - about half the world's mammal species are rodents, but they entered Australia relatively recently, when Australia and New Guinea drifted close enough to southeast Asia for temporary land bridges to form).

In Australia all native rodents are in the rats-and-mice family (i.e. there are no squirrels, porcupines, beavers etc. native to Australia). The ancestors of the native rats and mice appear to have arrived in Australia around 4 million years ago and have diversified since then into many different species, especially in drier regions (although several species are very common in our rainforests).

Seals and sealions

Seals

Seals belong to family Phocidae, and have no external ears.
None currently breed on Australian coastlines, and are more animals of the Sub-Antarctic islands and Antarctica itself.

Sea-lions and fur seals

Fur seals and sea-lions belong to the family Otariidae, and have visible ears.
Two species of fur seals breed in Australia, and another two on SubAntarctic islands
The Australian sea-lion is found only in Australia.

Dugong

The dugong is closely related to the manatees, and although a sea-dweller it is more closely related to elephants than to seals or whales.
It is unique amongst marine mammals in being entirely herbivorous.
It is found from the coastal waters near Brisbane northwards, around the northern tropical waters and down the west coast to a point roughly level with Brisbane. It's numbers are regrettably declining.

Whales and dolphins

Several species of dolphin inhabit waters around Australia, the most common being the bottle-nosed dolphin
Several shales migrate along the Australian coasts in winter, coming up from Antarctica to breed in warmer waters. The most commonly-seen in the south is the right whale, the most common on more northerly coasts being the humpback whale.


References and links


wikipedia - monotremes
comparisons between monotremes, and between monotremes and other mammals

The Australian Museum Complete Book of Australian Mammals (Angus & Robertson, 1983)  edited by R. Strahan has long been the standard reference to mammals of Australia. 'Mammals of Australia' by R. Strahan is a revision of this important document.

Other books on Australian mammals include:
 See also these references to Australian mammal books
The Australian Mammal Society was founded in 1958 to promote scientific study of the mammals of the Australian region.
See also the Australian Museum's comprehensive pages on Australian mammals



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