Australian megafauna

The term Australian megafauna refers to the megafauna in Australia^[1] during the Pleistocene Epoch. Most of these species became extinct during the latter half of the Pleistocene, and the roles of human and climatic factors in their extinction are contested.

There are similarities between the prehistoric Australian megafauna and some mythical creatures from the Aboriginal Dreamtime.^[2]

Causes of extinction

Many modern researchers, including Tim Flannery, think that with the arrival of early Aboriginal Australians (around 70,000~65,000 years ago), hunting and the use of fire to manage their environment may have contributed to the extinction of the megafauna.^[3] Increased aridity during peak glaciation (about 18,000 years ago) may have also contributed, but most of the megafauna were already extinct by this time.^{[citation needed]} Others, including Steve Wroe, note that records in the Australian Pleistocene are rare, and there is not enough data to definitively determine the time of extinction of many of the species, with many of the species having no confirmed record within the last 100,000 years. They suggest that many of the extinctions had been staggered over the course of the late Middle Pleistocene and early Late Pleistocene, prior to human arrival, due to climatic stress.^[4]

Procoptodon goliah reconstruction

Genyornis newtoni

New evidence based on accurate optically stimulated luminescence and uranium-thorium dating of megafaunal remains suggests that humans were the ultimate cause of the extinction for some of the megafauna in Australia.^[5]^[6] The dates derived show that all forms of megafauna on the Australian mainland became extinct in the same rapid timeframe—approximately 46,000 years ago^[1]—the period when the earliest humans first arrived in Australia (around 70,000~65,000 years ago long chronology and 50,000 years ago short chronology).^[3] However, these results were subsequently disputed, with another study showing that 50 of 88 megafaunal species have no dates postdating the penultimate glacial maximum around 130,000 years ago, and there was only firm evidence for overlap of 8-14 megafaunal species with people.^[4] Analysis of oxygen and carbon isotopes from teeth of megafauna indicate the regional climates at the time of extinction were similar to arid regional climates of today and that the megafauna were well adapted to arid climates.^[5] The dates derived have been interpreted as suggesting that the main mechanism for extinction was human burning of a landscape that was then much less fire-adapted; oxygen and carbon isotopes of teeth indicate sudden, drastic, non-climate-related changes in vegetation and in the diet of surviving marsupial species. However, early Aboriginal peoples appear to have rapidly eliminated the megafauna of Tasmania about 41,000 years ago (following formation of a land bridge to Australia about 43,000 years ago as Ice Age sea levels declined) without using fire to modify the environment there,^[7]^[8]^[9] implying that at least in this case hunting was the most important factor. It has also been suggested that the vegetational changes that occurred on the mainland were a consequence, rather than a cause, of the elimination of the megafauna.^[7] This idea is supported by sediment cores from Lynch's Crater in Queensland, which suggest that fire increased in the local ecosystem about a century after the disappearance of Sporormiella (a fungus found in herbivorous animal dung used as a megafaunal proxy), leading to a subsequent transition to fire-tolerant sclerophyll vegetation.^[10]^[11]^[12] However, the use of Sporormiella as a megafaunal proxy has been criticised, noting that Sporormiella is found sporadically in the dung of various herbivorous species, including extant emus and kangaroos, not just megafauna, that its presence depends on a variety of factors, often unrelated to megafaunal abundance, and that in Cuddie Springs, a well known megafaunal site, the densities of Sporormiella were consistently low.^[13] A study of extinct megafauna at the Walker Creek site in Queensland, found that their disappearance from the site after 40 kya came after an extended period of environmental deterioration.^[14]

Chemical analysis of fragments of eggshells of Genyornis newtoni, a flightless bird that became extinct in Australia, from over 200 sites, revealed scorch marks consistent with cooking in human-made fires, presumably the first direct evidence of human contribution to the extinction of a species of the Australian megafauna.^[15] This was later contested by another study that noted the too small dimensions (126 x 97 mm, roughly like the emu eggs, while the moa eggs were about 240 mm) for the Genyornis supposed eggs, and rather, attributed them to another extinct, but much smaller bird, the megapode Progura.^[16] The real time that saw Genyornis vanish is still an open question, but this was believed as one of the best documented megafauna extinctions in Australia.

"Imperceptive overkill", a scenario where anthropogenic pressures take place, slowly and gradually wiping the megafauna out, has been suggested.^[17]

On the other hand, there is also evidence to suggest that (contrary to other conclusions) the megafauna lived alongside humans for several thousand years.^[18]^[19] The question of if (and how) the megafauna died before the arrival of humans is still debated; with some authors maintaining that only a minority of such fauna remained by the time the first humans settled on the mainland.^[20] One of the most important advocates of human role, Tim Flannery, author of the book Future Eaters, was also heavily criticised for his conclusions.^[21]^[22] A surprisingly late date of 33-37 kya is known for a Zygomaturus specimen from the Willandra Lakes Region in New South Wales, the latest known date for any Australian Megafauna. This is well after aboriginal arrival in Australia around 50 kya.^[23]

A 2021 study found that the rate of extinction of Australia's megafauna is rather unusual, with some more generalistic species having gone extinct earlier while highly specialised ones having become extinct later or even still surviving today. A mosaic cause of extinction with different anthropogenic and environmental pressures was proposed.^[24]

Living Australian megafauna

The term "megafauna" is usually applied to large animals (over 100 kg (220 lb)). In Australia, however, megafauna were never as large as those found on other continents, and so a more lenient criterion of over 40 kg (88 lb) is often applied.^[25]

Marsupials

A red kangaroo

The red kangaroo (Osphranter rufus) grows up to 1.8 m (6 ft) tall and weighs up to 85 kg (187 lb). Females grow up to 1.1 m (3 ft 7 in) tall and weigh up to 35 kg (77 lb). Tails on both males and females can be up to 1 m (3 ft 3 in) long.^{[citation needed]}
The eastern grey kangaroos (Macropus giganteus). Although a male typically weighs around 66 kg (145 lb) and stand almost 2 m (6 ft 7 in) tall, the scientific name Macropus giganteus (gigantic large-foot) is misleading, as the red kangaroo living in the semi-arid inland is larger.
The antilopine kangaroo (Osphranter antilopinus), sometimes called the antilopine wallaroo or the antilopine wallaby, is a species of macropod found in northern Australia at Cape York Peninsula in Queensland, the Top End of the Northern Territory, and the Kimberley region of Western Australia. They can weigh as much as 47 kg (104 lb) and grow over 1 m (3 ft 3 in) long.
Common wombats (Vombatus ursinus) can reach 40 kg (88 lb). They thrive in Eastern Australia and Tasmania, preferring temperate forests and highland regions.

Birds

A southern cassowary

The emu (Dromaius novaehollandiae)
The southern cassowary (Casuarius casuarius)

Reptiles

A perentie

Goannas, being predatory lizards, are often quite large or bulky, with sharp teeth and claws. The largest extant goanna is the perentie (Varanus giganteus), which can grow over 2 m (6 ft 7 in) in length. However, not all goannas are gargantuan: pygmy goannas may be smaller than a man's arm.
A healthy adult male saltwater crocodile (Crocodylus porosus) is typically 4.8–7 m (15 ft 9 in – 23 ft 0 in) long and weighs around 1,000 kg (2,200 lb)), with many being much larger than that.^[26] The female is much smaller, with typical body lengths of 2.5–3 m (8 ft 2 in – 9 ft 10 in). An 8.5 m (28 ft) saltwater crocodile was reportedly shot on the Norman River of Queensland in 1957; a cast was made of it and is on display as a popular tourist attraction. However, due to the lack of solid evidence (other than the plaster replica), and the length of time since the crocodile was caught, it is not considered "official".^{[clarification needed]}
The freshwater crocodile (Crocodylus johnstoni) is a relatively small crocodilian. Males can grow to 2.3–3 m (7 ft 7 in – 9 ft 10 in) in length, while females reach a maximum length of 2.1 m (6 ft 11 in). Males commonly weigh around 60 kg (130 lb), with large specimens up to 85 kg (187 lb) or more, as against the average female weight of 20 kg (44 lb). In places such as Lake Argyle and Nitmiluk National Park (Katherine Gorge), there exist a handful of confirmed 4-metre (13 ft) individuals.

Extinct Australian megafauna

The following is an incomplete list of extinct Australian megafauna (monotremes, marsupials, birds and reptiles) in the format:

Latin name, (common name, period alive), and a brief description.