Reconsidering Kangaroos #1

It's been some four years since I posted on kangaroos and in the meantime our understanding of the relationships of different kangaroo groups to each other has changed considerably, so it's probably time to revise and update that post. Moreover that post was only on the 'main line' of kangaroos and I've been meaning for some time to add a post on the 'other', equally interesting, members of the family. That will finally occur next week!

The story of people and kangaroos in Australia is at least 60,000 years old (and almost that old in New Guinea) but that story isn't mine to tell. The first kangaroo (and I'll be defining my terms soon) to have the misfortune to be killed by a European seems to have been a Dusky Pademelon Thylogale brunii on the South Coast of New Guinea in 1606, by Captain Don Diego de Prado y Tovar. Prado, apparently a Spanish nobleman, was in command of the San Pedrico which accompanied Luis Váez de Torres on the expedition which sailed between New Guinea and Australia, through the strait that now bears Torres' name. Soon afterwards, in 1629, the Dutchman Francisco Pelsaert described the first Australian kangaroo, probably a Tammar Wallaby Notamacropus eugenii, while rescuing survivors of the Batavia disaster off the west coast of Western Australia. The first English account was by naturalist-pirate William Dampier in 1699 also from northern Western Australia, seemingly this time the fascinating Banded Hare-wallaby (see next week).

All this means that when Captain James Cook's crew encountered (and cooked) Eastern Grey Kangaroos in northern Queensland in 1770, they were not quite as surprised by the creatures as they are sometimes portrayed as being.

Eastern Grey Kangaroos Macropus robustus, Namadgi National Park, south of Canberra.

In vernacular, we tend to use 'kangaroo' for the larger members of the family Macropodidae (which has some 60 members), and 'wallaby' for smaller ones, but it's not taxonomically meaningful. Indeed until very recently all the best-known Australian kangaroos and wallabies were included in just one genus Macropus (ie 'big foot'), from which the kangaroo family name Macropodidae derives. I use 'kangaroo' loosely to refer any member of the family, but better still is the word macropod, which I'll use from now on. 

It was only by accident - literally - that we use the word kangaroo, that being the name for Eastern Grey Kangaroo in the Guugu Yimithirr language of north Queensland. It came to our attention when Cook's Endeavour struck a reef in 1770 near where Cooktown now stands, necessitating an extended stay, during which naturalist Joseph Banks learnt the word for the animal his greyhounds caught. I like to muse that had Cook sailed on by, as he'd intended, we'd almost certainly be calling them something like Patagarang or Badagarang, that being the word in the language of the people who lived in the area where the first settlement intruded on them, in 1788 where Sydney now stands. 'Wallaby' also comes from the language of the Sydney people (a language often referred to as Dharug, though there seems to be some doubt about that), apparently being the word for what we call Swamp or Black-tailed Wallaby Wallabia bicolor. 

And to head off another oft-asked question, 'wallaroo' is not a kangaroo-wallaby hybrid, but any of three species of mostly stocky muscular hill kangaroos; unfortunately the hybrid name furphy was recently perpetuated again in a widely read on-line ABC story on kangaroos. Wallaroo is yet another Sydney language word. This term is used for Osphranter robustus along the Great Dividing Range along the east coast, while the word Euro (from the Adnyamadhanha language of the Flinders Ranges in South Australia) is used throughout the inland for the same species.

Wallaroo, Nangar NP, New South Wales.
Wallaroos (mostly from the Great Dividing Range) are blue-grey, while Euros (from the drier inland)
are reddish grey, despite being the same species.
Note the shaggy coat and big ears.

Euros, Broken Hill, far western New South Wales, in typical rocky range habitat.

Those who are familiar with kangaroo species names might now be getting agitated about my use of unfamiliar genus names Notamacropus and Osphranter instead of the familiar Macropus. May I explain my temerity? Macropus as we generally understand it was not always set in stone. Osphranter was actually coined by Gould back in 1842 for the euros and, despite being included in Macropus by some authorities later in the 19th century, Osphranter was still being used by respected macropod taxonomists such as Ellis Troughton and Tom Iredale into the second half of the 20th century. (At this stage, and even later, Megalaia was also widely used for the Red Kangaroo.) In 1985 Terence Dawson (one of the greatest kangaroo field ecologists of all) and Tim Flannery, eminent marsupial zoologist (et alia!), proposed three sub-genera within Macropus. Macropus itself contained just the two grey kangaroos; Osphranter held the three wallaroos plus the Red Kangaroo; Notamacropus comprised the 'main line' wallabies. This was widely accepted by science, but had little effect on the wider world, as no-one else takes much notice of sub-genera.

This changed in 2015 with the monumental tome Taxonomy of Australian Mammals, by Stephen Jackson (widely published on marsupials, working for NSW government) and Colin Groves (of the Australian National University, and a doyen of world mammal taxonomy until his untimely death last year). They raised the three sub-genera to full genus level and I found their reasoning to be interesting, and indeed refreshing. "... we urge an objective standard for the recognition of genera, and ... the only one that seems readily applicable is time depth; and our preferred time depth for a genus is 4-5 million years." These three groups seem to have separated 8-9 million years ago, so readily meet this criterion. Indeed, the proposal seems to have been near-universally accepted by those in the field, so I could hardly do otherwise, even were I so inclined.

I hear so many stories of people coming to Australia and expecting to see kangaroos in the main streets that I suspect that some of them must be true. And here in Canberra it's pretty close to the way things are! In suburbs near the numerous hill reserves which are scattered through the urban area it's common to see roos grazing the lawn or drinking from garden ponds in dry spells. And driving anywhere in Canberra can be potentially hazardous when the roos are on the move. I could meet you at the airport and pretty much guarantee to find you Eastern Grey Kangaroos within about 10 minutes. The abnormally very high numbers of this species in precious Canberra grassy woodland reserves has led to science-based regular culls to keep kangaroo numbers within sustainable levels, which has of course led to community conflict. No sane person enjoys killing animals, but our stewardship of the natural world comes with sometimes difficult responsibilities.

Eastern Grey Kangaroos Macropus giganteus, just a few minutes from my Canberra suburban home.

The animals in this photo are showing the classic kangaroo characteristics of powerful hind legs, short forelimbs with grasping paws and a long heavy counter-balancing tail. Lounging about stretched out on the ground is typical daytime behaviour too.

Eastern Grey Kangaroo lounging, Mulligans Flat Nature Reserve, northern Canberra.

The long hind legs are an adaptation to hopping, a form of locomotion which seems to have arisen in the ancestral kangaroos somewhere between 15 and 20 million years ago, though this is a relatively unusual situation where the fossil record has so-far unfilled and frustrating gaps. While members of a few rodent families, and a member of one other family of small marsupials (the carnivorous Kultarr) have independently evolved hopping, the kangaroos are the only large vertebrates ever to have developed the trick. (Tales of hopping dinosaurs seem to be no more than tales.)

Eastern Grey Kangaroos on the move.

The leaps that these legs can power are sometimes astonishing. These Eastern Greys were moving back from early
morning feeding in the paddocks to the shelter of Mt Ainslie Nature Reserve. Most went under the fence, as is
normal - I was still probably 100 metres away and they were in no panic - but this relatively young
animal went over the fence from a standing jump with little effort.
You can see the height of the fence relative to the size of the hopper.

Hopping is not an efficient mode of locomotion at low speeds; at less than 12km an hour a trotting dog for instance uses less energy. As speed increases however the hopping kangaroo begins to pull ahead energetically, and increases its relative efficiency further as its speed increases. At 22km per hour, the highest speed that I'm aware that energy expenditure has been measured, a hopping kangaroo uses less than 75% of the energy a similarly sized dog would. At speeds of 40kph - which a kangaroo can readily achieve - it would be expected to be twice as efficient. 

The reason for this has been tentatively suggested in terms of the muscles and tendons acting like springs, storing kinetic energy which is used in the next leap. Doubtless this occurs, but we now know that galloping animals also utilise this 'bouncing ball' strategy, so a roo's advantage can't be attributed solely to this. It seems that the explanation lies in the much longer stride a hopping kangaroo can achieve. An animal can increase speed either by taking longer strides, or by taking more steps or hops per minute; it is the latter which uses much more energy. A kangaroo's gait allows it to simply to take longer and longer hops as it accelerates, to more than four metres per bound. At very high speeds it will also start to put in extra hops, which presumably uses more energy.

At very low speeds however, such as when feeding, a kangaroo 'caterpillars' along, using five limbs, the tail being co-opted for this purpose. 

Big male Eastern Grey Kangaroo, Namadgi National Park.
To get to the next patch of desirable grass, the animal swings its back legs forward together,
while balancing on its forelegs and tail.

As we approached he simply rose and began hopping to put a bit of distance between us.

Curiously, when swimming, a kangaroo suddenly learns how to move its hind legs independently of each other, the only time it seems able to do so.

The drive from the ground is conveyed by an elongated fourth toe and strong claw, as demonstrated by this laid-back wallaby.

Extremely relaxed Red-necked Wallaby N. rufogriseus, Mount Clunie, near Kyogle, northern New South Wales;
note the long fourth toes and strong claws, on either side of the tail.

Tail, hind legs and the wicked fourth claw are all used in combat too - in defence against predators (especially dogs and dingoes), and in fights with rival males over mating rights. Usually such fights are largely ritualised demonstrations of strength and experience, but when in earnest real damage can be done by the power of the legs and the tip of the claw.

As can be seen here (in Namadgi National Park, south of Canberra) the male balances briefly on his tail
while launching a kick - with limited intent of malice in this case. The imposing front claws too can be
used to attack the opponent's face, so the head is usually held back by the defender.

As marsupials, embryos develop externally, but in the pouch (ie the marsupium). In the case of the big kangaroos time in the pouch varies with species from 200 to 300 days.

Agile Wallaby Notamacropus agilis with joey, Cape Hillsborough NP, tropical Queensland.
This one is starting to explore the world, but retreats to safety when it feels the need.

Eastern Grey Kangaroo, Canberra. The joey dives in head-first, then reorganises itself while inside.

More seasonal climate species, such as the Eastern and Western Grey Kangaroos M. fuliginosus, breed seasonally, but the extended pouch life means that the female is usually caring for a pouch young and a still dependent joey 'at foot', who follows her around and feeds from her. Arid land species, such as Red Kangaroos and Euros, tend to breed continuously. In either case the female produces quite different types of milk from the two teats (protected in the pouch), with one of them elongated to assist the youngster leaning in from outside to feed. (It was long believed that the joeys developed directly from the teats.) Furthermore Red Kangaroo females will at any one time be not only caring for a pouch young and dependent joey, but will also be carrying a blastocyst (an embryo 'frozen' in development at only a few cells, some 0.25mm in diameter). This is released to grow when either the mother loses the pouch young, or it leaves the pouch as it grows. This is an adaptation to living in the boom and bust of an El Niño climate; populations can crash during droughts, and rebound rapidly in the irregular and non-seasonal good years.

There is of course a lot more to say, and I'll be saying some of it next week, but you've probably read more than your fill for now. Let's finish with a partial gallery of the kangaroos until recently called Macropus, though I'm missing four of the thirteeen living species. (These are Parma Wallaby N. parma, rediscovered in the wild in northern NSW coastal forests in 1967 after a 100 year hiatus; the Black-striped Wallaby N. dorsalis, a shy nocturnal dweller of dense NSW and Queensland shrublands; the Western Brush Wallaby N. irma of south-western Australian heathlands; and the rare and little-known Black Wallaroo O. bernardus of the sandstone escarpments of Kakadu NP and the immediate surrounds. I've seen the Black-striped and Western Brush Wallabies, but have no usable photos; pictures are easy to find on line though if you're interested.)

Big male Eastern Kangaroo, Canberra.
Like most of the big kangaroos (though not many smaller macropods), Eastern Greys have benefited
greatly from agriculture, which supplies pastures and water points. They are expanding well out of their
traditional range into the semi-arid zone, utilising farm dams.

Western Grey Kangaroos:
female, Cape Le Grande NP, Western Australia (above);
big male, Silverton, far western New South Wales, below.

Western Greys are really brown. They evolved in Western Australia when the south-west
was isolated from the east by arid conditions, and later spread east. They were only recognised
as forming a separate species from the Eastern Grey in recent decades.

Red Kangaroos M. rufus; Western Australia (above), south-west Queensland (below).
This beautiful animal is found throughout the arid inland.
Theoretically males are red and females blue-grey, but a substantial proportion of animals (varying
between populations) has the 'other' colour, or a blend.

Wallaroo, Nangar National Park, New South Wales.

Euro, Idalia NP, south-western Queensland

Big male Euro in stand-off with a Dingo, Telegraph Station Reserve, Alice Springs.

Kangaroo cave painting, Burrungkuy, or Burrunggui (formerly erroneously known as Nourlangie Rock),
Kakadu National Park, Northern Territory.
In this sandstone habitat, the painting probably represents a Euro.

Antilopine Wallaroos O. antilopinus, Kakadu NP.
This is the kangaroo of the tropical savannahs.

Agile Wallaby, Kakadu National Park.
Also a tropical macropod, though one that goes into the brushes more than the Antilopine does.

Male Agile Wallaby, Tyto Swamp, Ingam, north Queensland, in pre-dawn light.
The notably narrow face is obvious here.

Red-necked Wallabies N. rufogriseus, Namadgi NP, near Canberra, above and below.

The origin of the species name, rufogriseus, 'red and grey', is obvious.

In Tasmania (here Ben Lomond NP) the same species is known as Bennett's Wallaby.

Tammar (or Dama) Wallaby M. eugenii, Kangaroo Island, South Australia.
This engaging little animal is still common there, but scarce on the adjacent mainland
and in south-western Western Australia.

Whiptail (or Prettyface) Wallaby M. parryi, Undara NP, north Queensland.
This elegant wallaby is found throughout coastal and hinterland
tropical  and subtropical eastern Australia.

I hope you've enjoyed this brief introduction to a group of marsupials that many of us here take for granted, though they are fascinating and intrinsically beautiful and we should never do so. Next time I'll talk about the rest of the macropods in other genera.

 

You can find the next and final instalment here.

NEXT POSTING THURSDAY 21 FEBRUARY
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