Research website of Dr Gilbert Price

Archives for September 2017

Revealing the life and times of an Ice Age giant

My team and I have just had a new study published that that looked at the question of migration in a species of giant, now-extinct, Ice Age megafauna of Australia.

The beast under the ‘microscope’ is Diprotodon optatum, famous for being the largest marsupial that ever existed. It stood 1.8 metres tall at the shoulder and weighed in at around 3,000 kg.

A herd of Diprotodon being stalked by the giant lizard, Megalania, while a couple of megafaunal kangaroos look on (image: Laurie Beirne)

A herd of Diprotodon being stalked by the giant lizard, Megalania, while a couple of megafaunal kangaroos look on (image: Laurie Beirne)

Diprotodon was one of the very first fossil animals ever described from Australia. Subsequent fossil records show that it had a near cosmopolitan distribution across Ice Age Oz, plus was one of the last surviving members of the megafauna.

But there’s a lot that we just don’t know about this animal, such as how it responded to seasonal changes; what its ecological role was; it’s basic biology… important questions that are critical in helping us understand why we don’t have Diprotodons anymore.

 

What we did

Our new study focussed on the life and times of an individual that once called the Darling Downs of southeast Queensland its home. We wanted to know what it ate, if it was a migratory species, and how it responded to changes in its environment.

Unlike some of their placental cousins, most modern marsupials don’t migrate at all. Some species, such as Red kangaroos (Macropus rufus) occasionally exhibit ‘nomadic’ migration where an individual or two will leave a home range, but with no specific plan or intention to return.

But what about Diprotodon? Weighing in at three tonnes, it’s more than 30 times the mass of the largest living marsupial, and likely had a very different ecological role when alive.

We applied a variety of geochemical analyses to a Diprotodon incisor tooth that we had borrowed from the Queensland Museum.

Diprotodon had ever-growing front chompers, so we predicted that our geochemical analyses (including carbon, oxygen, and strontium isotopes) would reveal lifetime changes in things like diet, water intake, plus also information about possible migration.

 

What we found

Without getting into the nitty gritty details, our study yielded some fascinating results. Firstly, our Diprotodon was clearly a seasonal migrant. It would undertake massive round-trips of up to 200 km per year as it tracked its preferred food source (basically, a combination of different species of grasses and leaves).

This is known as ‘two-way’ migration and is an evolutionary response to annually fluctuating resources.

 

Our discovery of such migration is a first for any marsupial living or extinct. That’s wildly fascinating in itself because marsupials have been around for a very long time. In fact, marsupials and their broader cousins, the metatherians (the group that includes all modern marsupials, but not placental or egg-laying mammals), have been on Earth for at least 160 million years. And until now, none have been known to have conducted such migration.

But perhaps more importantly, our data suggest that Ice Age Australia was just so ecologically different to anything that we’ve previously imagined.

In fact, the palaeo-ecosystem that we envisage seems more like the modern Serengeti than anything that we have Downunder today.

 

Some burning questions

Zebra are modern migrating mammals of East Africa's Serengeti

Zebra are migrating mammals of East Africa’s Serengeti

At the end of the day, we’re left with even more questions than what we started out with. Which other megafaunal species migrated? What were the consequences of their removal from Ice Age ecosystems? And especially, what are the implications for understanding Australia’s modern ecology?

These are major questions that need to be addressed, and will form the focus of future investigations.

We are massively appreciative of all the institutions that supported this research: The University of Queensland, University of Rochester, Southern Cross University, and Griffith University. Huge thanks to the Queensland Museum (and especially Kristen Spring) for their support, Nathan Siddle for making the 3D model, and the Australian Research Council for funding this research.

Is the Tasmanian Tiger really extinct?

There’s been a flurry of media reports out this year that have asked the question: Is the Tasmanian Tiger really extinct? Many of the stories are based off a media release put out by James Cook University where a couple of their researchers have plans to set-up a camera trap survey in north Queensland in search of this enigmatic marsupial.

Tasmanian Tigers, otherwise known as ‘Thylacines’ or ‘Marsupial wolves’, are thought to have suffered extinction on the 7th of September, 1936. That might sound like a very specific date to know when anything went extinct, and it is. But there’s quite a tragic story behind it.

 

The demise of the Tasmanian Tiger

Most people will know that Tasmian Tigers were the top land-dwelling predator in Tasmania until British colonisation. A devastating combination of over-hunting, competition with feral dogs, and exposure to new foreign diseases, did not bode well for their survival.

In 1901, the Tasmanian Government recognised that they had a conservation problem on their hands… but did nothing serious to remedy the situation until it was too late.

It wasn’t until the 10th of July, 1936, that legislation was finally passed that allowed for the protection of the Tasmanian Tiger. At that stage, Tasmanian Tigers hadn’t been reliably recorded in the wild for several years. In fact, the only known living member of the species at the time was Benjamin, a young adult male in Hobart’s Beaumaris Zoo.

Thylacine hunter

Thylacine hunter

Sadly, on one cold night in September 1936, a keeper forgot to let Benjamin back into his shelter and he was found deceased, exposure being the killer.

59 days.

59 days from the time that the Tasmanian Tiger was officially protected, to the time that the last known individual died.

 

But what if Tasmanian Tigers aren’t actually extinct?

Since 1936, there have been numerous but hitherto unverified reports of Tasmanian Tiger sightings. But is that about to change now that Science has become more involved?

It was interesting to read the plethora of comments that the public have left on the recent news articles and in social media. They vary from “hey, this is cool!” to “if they’re really out there, just let them be!”

As someone who researches, writes, and teaches science, I’m very much in the “this is cool” camp, but with a caveat. We can’t save what we don’t know about. I think that the key to conservation and environmental management is public awareness and education.

All that aside though, the recent media reports did get me thinking. What if Tasmanian Tigers aren’t really extinct? Could there be a viable population living in remote parts of north Queensland?

We know on the basis of the fossil record that Tasmanian Tigers did once live on the mainland. In fact, prior to around 4,000 years ago, Tasanian Tigers also used to call New Guinea their home.

 

An unexpected discovery

My crew and I went on a fieldtrip a couple of years ago to some caves west of Townsville in north Queensland. Squirming around on my stomach in a tight squeeze of one particular cave, I stretched out my hand and picked up a bunch of loose teeth from the surface. It was an amazing moment for me and something that I’ll never forget: they were the teeth of a Tasmanian Tiger.

Fossil Tasmanian Tiger teeth from a cave in North Queensland

Fossil Tasmanian Tiger teeth from a cave in North Queensland

They were discoloured, so not quite the pearly whites that you’d expect with fresh teeth, but they were remarkably well-preserved. Both the crowns and roots were completely undamaged. That’s very unusual for any type of fossil, so you can imagine my surprise to find them like that.

Does this astonishing preservation and fact that they were found simply lying on the surface mean that they are actually really young?

I’ve not yet had an opportunity to fully analyse and date the teeth yet, but wouldn’t it be amazing if they were from an animal post-dating 1936. It would certainly challenge everything that we know about Tasmanian Tiger and their supposed time of extinction, not to mention also giving credence to anyone who has claimed to have seen a living Tasmanian Tiger on the mainland.

Better get to the lab…!