The resurgence of red kangaroos
SAND DUNE AND gibber plain. The Sturt Stony Desert stretches from horizon to horizon in Australia’s heartland, its varnished, stony surface reflecting the heat, making this a land of bizarre mirages. It is one of the most unforgiving corners of our harsh land. Averages out here mean nothing.
For decades the country can lie baking under the pitiless sun. But sudden changes, originating far away in the Indian and Pacific oceans, can trigger widespread rain, turning it into a Garden of Eden. And when that happens – as it has in the last few years – every living thing changes gear. Seeds that have lain dormant spring to life. Aestivating frogs shrug off their torpor and struggle to the surface, while small mammals breed as if there’s no tomorrow. Soon, the desert is carpeted in grasses and herbs, and throbbing with life.
In 1974 I was lucky enough to see the phenomenon for myself. I was in the Lake Frome Basin as a volunteer on a fossil dig, excavating the 30-million-year-old bones of creatures that once lived in rainforests, when great thunderstorms rolled in. Soon our excavations were waterlogged and tracks impassable, so we sat in camp and watched the spectacle.
Over the course of a single night frogs emerged by the tens of thousands, overrunning our campsite. Their croaking was so loud we couldn’t sleep. Within weeks a carpet of green had spread under the gaunt mulgas, and flowers were blooming everywhere – white daisies on the dunes and purple parakeelya in the swales. The daisies were heliotropic; I awoke one night to find entire fields of them pointing towards the full moon.
Red kangaroos: outback mammals
The largest native mammal of Sturt Stony Desert is the red kangaroo. It is also the world’s largest living marsupial, and its response to the rains is wondrous. In dry times the females may wait five years before becoming sexually mature, but when it’s wet they’ll begin reproducing at 18 months. And from then on they are a reproductive production line. Permanently pregnant, they’re perpetually poised to take advantage of the rains. In a good season they carry three young, all at different stages of development. The furthest along are the young at foot.
They’re still drinking milk from an elongated teat, but no longer climb into the pouch, which is occupied by a smaller young attached to its own teat. Remarkably, the composition of the milk produced by the two teats differs – it is tailored to suit the needs of the different-sized joeys.
The third young is not yet born: it enters a state of suspended animation when consisting of just a few hundred cells, and will recommence development soon after the oldest joey stops suckling. Then mum will mate and become pregnant again. Their overlapping generations maximise what may be a brief reproductive opportunity, which is just as well, for it might be decades before the big wet returns.
The big reds: majestic kangaroos
In the mid-19th century fears were held for the survival of the red kangaroo. John Gould placed it with the thylacine as a species likely to become extinct. But the rapid expansion of grazing pasture and the suppression of the dingo favoured it, and today it’s readily seen over much of the inland.
Whenever I see one up close, I’m enthralled by its beauty. The exquisitely fine, blue fur of the females – with their white undersides, tails and limbs – remind me of clouds. The big reds, as the males are known, have their own majesty: a rich red coat supplemented by a gorgeous pinkish-red stain, which is the product of a glandular secretion on the chest.
Weighing as much as 90kg when fully mature and standing on tiptoe at more than 2.2m tall, they have the muscled physique of a boxer. Their contests for mating rights, when rivals stand chest to chest to assert their dominance, grappling and rising on their tail to deliver powerful kicks, are among the inland’s greatest spectacles.
There is still much we don’t know about red kangaroos, including their evolutionary origins. They’re members of the wallaroo group, close to the antilopine wallaroo of northern Australia. But because their fossils are incredibly rare, when they arose as a distinct species is unclear. Some of the fossils that have been found have turned up in strange places, like the outskirts of Melbourne, where no reds exist today. These date back 20,000 years and tell of a time when conditions were much drier, the arid inland extending all the way south to Port Phillip Bay.
You may have to travel far inland to see red kangaroos today, but it’s well worth the effort, especially in a wet year such as this.
Source: Australian Geographic (Issue 109, July-August, 2012)
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