Saturday, 30 January 2016

New megafauna extinction evidence

This story from the ABC comes at a great time as the grade 6 kids will be creating PowerPoint projects on Australian megafauna.More than 85 per cent of Australia's large mammals, birds and reptiles disappeared after people arrived. 
There has been a long-running debate over whether people caused the extinction of Australia's unique collection of large animals, also including a 7.5 meters monitor lizard called Megalania, a nearly rhinoceros-sized wombat called Diprotodon, large marsupial predators and 450 kilogram kangaroos.( a skeleton of a Diprotodon can be found at the Melbourne Museum) 

The Genyornis (Facts)

Lived 1.8 million to 40,000 years ago
Flightless bird, taller and heavier than the modern-day emu
Co-existed with humans for 15,000 years
Last of the large "thunder birds" local to Australia
Fossils found in Mt Gambier, SA and NSW. Footprints found in dunes on southern Victoria
Now the mystery behind the big bird's extinction may have been solved, after burnt eggshells revealed people may have been the culprits.

Scientists revealed burn patterns detected on eggshell fragments showed the first humans to arrive in Australia, about 50,000 years ago, gathered and cooked the big birds' eggs.

The practise wreaked havoc with its reproductive success.

The study is the first to provide direct evidence early humans preyed on the remarkable large animals that once thrived in Australia, but disappeared after people arrived, University of Colorado geological sciences Professor Gifford Miller said.

The Genyornis was the last of the family of giant birds called Dromornithids or "thunder birds", which included birds as tall as three metres and as heavy as 500 kilograms.

The birds are related to ducks, geese and swans.

Genyornis vanished about 47,500 years ago, Professor Miller said.

The researchers analysed burned Genyornis eggshell fragments — some only partially blackened 
The eggs were the size of a rockmelon, weighing about 1.5 kilograms.

"We conclude the only explanation is that humans harvested the giant eggs, built a fire and cooked them, which would not blacken them, then discarded the fragments in and around their fire as they ate the contents," Professor Miller said.

"Wild or natural fires could not produce such patterns.

"We have no direct evidence that humans hunted the adults, but loss of eggs certainly reduced reproductive success."

How did Australia's big animals die?

 More than 85 per cent of Australia's large mammals, birds and reptiles disappeared after people arrived.
More than 85 per cent of Australia's large mammals, birds and reptiles disappeared after people arrived.

Some experts blame human hunting, while others blame climate shifts, in particular continental drying from about 60,000 to 40,000 years ago.

Professor Miller said the new study — published in the journal Nature Communications — strengthened the case for human impact.

Genyornis populations declined and became extinct over a short period of time. The bird lived in the dry grasslands and woodlands of southern and eastern Australia.

Fossils have since been found in Victoria, New South Wales and South Australia, especially on the surface of the dry Lake Callabonna.

The bones of a number of birds have been found in one place, suggesting they could have lived in flocks.

The Genyornis was believed to be depicted in ancient rock art after a red ochre painting was discovered at the centre of the Arnhem Land plateau in 2008.

The work — which at the time was believed to be Australia's oldest painting — depicted two emu-like birds with their necks outstretched.
Marsupial Lion

Marsupial lions were Australia's top mammalian predators, with meat-slicing teeth, razor-sharp claws and the ability to climb in caves where they reared their young communally, scientists have found.

The Flinders University research, published in Nature's Scientific Reports, reveals that the unique meat-eating mammals left thousands of claw marks on surfaces inside a limestone cave in south-western Australia.

The largest scratch marks in the caves could only have been made by adult lions," Associate Professor Prideaux said. Many of the smaller marks were made by juveniles: they have the same form as those of adults but do not match claw marks made by other known cave dwellers.

"Marsupial lions, like all marsupials, would have given birth to extremely underdeveloped young that could not be left alone until becoming at least partially weaned," he explained.

Caves provided a safe, climate-controlled environment for raising young. Among other things, the caves were defensible against carnivores such as thylacines, the Tasmanian doglike marsupials with stripes across their rumps.

Many of the Tight Entrance Cave claw marks were located on very steep surfaces up to three metres from the cave floor. "This was probably the quickest route to the exit hole in the cave roof," 

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