Tag Archives: climate change

What are megafauna?

By Rochelle Lawrence, Palaeontological Research Assistant, and Scott Hocknull, Senior Curator, Geosciences, Queensland Museum.

Megafauna are giant animals usually weighing over 44 kilograms (kg). Most megafauna are now extinct (no longer exist) and were closely related to living species of animals we see today. You have probably heard of the more commonly known megafauna species, like the saber-toothed cat and woolly mammoth from North America.

Here is a cast of a saber-toothed cat, Smilodon fatalis, from the La Brea Tar Pits in Los Angeles, California, United States of America, that I walk by in our Queensland Museum’s Geosciences collection. Image Credit: Rochelle Lawrence.

However, Australia is unique with its own megafauna ranging from huge and sometimes strange marsupials (mammals with a pouch), like the giant sloth bear-like Palorchestes to very large monitor lizards like the giant goanna, Megalania. There were giant wombat-like marsupials the size of a rhinoceros like Diprotodon, an array of giant kangaroos different to today’s species and a weird super-predator called Thylacoleo, which means pouched-lion. Australia even had giant, armoured tortoises with clubbed tails, land-dwelling crocodiles, giant constricting snakes and huge flightless birds.

Reconstruction of one of my favourite megafauna, Palorchestes. Image Credit: Andrey Atuchin, Rochelle Lawrence, Scott Hocknull © Queensland Museum.

Megafauna can also refer to species that weighed less than 44 kg, but resemble a giant version of a closely related living species. For example, the extinct ‘giant’ koala (Phascolarctos stirtoni) was larger than the living koala (Phascolarctos cinereus) and probably weighed under 15 kg. Others include a giant echidna, (Megalibgwilia), the Thylacine or Tasmanian Tiger and a larger relative of the Tasmanian devil, Sarcophilus laniarius. The term ‘megafauna’ is still used to refer to our largest living animals today such as the elephant.

Can you think of any other living megafauna or extinct?

A species of living megafauna, the elephant, we saw on safari in Namibia, Africa. Image Credit: Rochelle Lawrence.

The megafauna arose well after the extinction of the dinosaurs at the end of the Cretaceous Period, 66 million years ago. In Australia they reached their largest size during the Quaternary Period (2.58 million to 11,700 years ago). The rapidly changing climatic and environmental conditions created grasslands and open habitats favouring the worldwide evolution of gigantic animals. Towards the end of the Quaternary, extinctions of megafauna occurred with nearly two-thirds of Australia’s largest animals dying out, along with many smaller species.

Skeletons of extinct megafauna, including the woolly mammoth, we saw in the Palaeontological Museum of Liaoning in China. Image Credit: Rochelle Lawrence.

There is a great debate in palaeontology (study of ancient life) and archaeology (study of human history) surrounding the big questions of why and how did the megafauna go extinct? Answers revolve around an extended period of severe climate change or human activity, or a combination of both, resulting in extreme changes to the environment. To answer these questions, we have to keep searching for the evidence and investigate more megafauna fossil sites – if they have been lucky enough to be preserved and can be found! Each individual site is a reflection of the different creatures and environmental conditions that existed within the ecosystem of that region representing a small piece of a bigger puzzle involving the whole of Australia and even the world. 

Reconstruction of a Diprotodon who had met its fate. Image Credit: Robert Allen © Queensland Museum.

Climate change here refers to the long-term, natural processes that can change the Earth’s climate such as its orbit around the Sun, changes in solar radiation, levels of greenhouse gases, and plate tectonics (movement of the Earth’s crust). These changes appear locally in the form of sustained changes in weather patterns, like decreases and increases in temperature, the frequency of droughts or flooding and overall intensifying aridity. Human activity during this time refers to hunting and disturbance patterns to the environment such as the burning of the landscape.

The drying and cracking of the earth I captured in outback Queensland. Image Credit: Rochelle Lawrence.

Today climate change includes anthropogenic drivers, like pollution from increased industrial activities of humans. Some of these include the burning of fossil fuels that generate extra greenhouse gases, pollutants and deforestation. These influence how the temperatures across the globe are regulated and drive global warming, a rise in the average temperature of the Earth’s climate system.

Smog from pollutants, such as cars, released into the atmosphere surrounding a bustling city in Asia. Image Credit: Rochelle Lawrence.

Megafauna fossils have been found around Australia and throughout Queensland. Those from the Quaternary Period have been found within sites in southern Queensland like the Darling Downs and Eulo. These sites are well known for the world’s largest wombat-like marsupial, Diprotodon optatum. Diprotodon would have browsed and grazed through the open woodlands and grassy plains of the downs and around the mud springs of Eulo, where on occasion they got stuck, leaving their bones for us to find tens of thousands of years later.

During this excavation we used the numbers to show where the bones of Diprotodon are situated within the ancient mud spring near Eulo. Image Credit: Rochelle Lawrence.

As we head north into the subtropics of central eastern Queensland we find fossils of megafauna from The Caves region near Rockhampton. The fossil remains of these animals that lived around and inside the cave systems have accumulated in cave chamber deposits. These deposits are unique as they record fossil fauna from different environments that transitioned through time from wet rainforests to dry open-arid habitats and then to today’s special vine thicket refugia (habitat supporting refuge). Here we find fossils of the extinct giant tree-kangaroo, Bohra, who is a larger version of today’s living tree-kangaroo species found in Far North Queensland and New Guinea.

Reconstruction of Bohra from the rainforest deposits. Image Credit: Robert Allen © Queensland Museum.
Dig pit in Colosseum Chamber of Capricorn Caves preserving fossils of animals from modern refugia. Image Credit: Rochelle Lawrence.

Even further north in Queensland, west of Mackay, fossils of megafauna are being excavated from sites at South Walker Creek. These fossil deposits are rare because they preserve a tropical megafauna. Not many megafauna fossil sites have been found in northern Australia. Many of the fossil bones have puncture marks made by predatory crocodiles including the extinct giant freshwater crocodile, Pallimnarchus. These crocodiles would have inhabited the billabongs and creeks, hunting at their edge for unaware megafauna that would come to drink.

Reconstruction of Pallimnarchus. Image Credit: Robert Allen © Queensland Museum.

Research into the megafauna is helping us understand their responses to environmental change during the Quaternary Period and hopefully it will answer the many questions surrounding their extinction. If we can track down our past, we can better understand how our present has been shaped by the extinction of the megafauna and hopefully use that knowledge to prepare for the future impacts of environmental change.

Can you think of any impacts to our environments today that affects our living species?

Project DIG is a partnership between Queensland Museum and BHP that will digitise and scan our collections and research for people worldwide. Check out our Tropical Megafauna in 3D!

Top Image – Reconstruction of megafauna from the Darling Downs. Image Credit: Robert Allen © Queensland Museum.

Rock Refugia

Patrick Couper is Curator of Reptiles and Amphibians at Queensland Museum and has an active interest in the taxonomy, ecology and conservation of Queensland’s diverse reptile fauna.

Patrick Couper

A major focus of Patrick’s research has been the discovery and description of leaf-tailed geckos that live in the rainforests of eastern Australia. Leaf-tails, which have a long rainforest ancestry, often have strong associations with rocky outcrops. Rocky areas have provided a safe haven for these animals through past periods of climate change. Patrick and Conrad Hoskin (James Cook University, Townsville) have termed such areas, lithorefugia. (Refugia are areas where special environmental conditions have enabled a species or a community of species to survive despite their extinction from surrounding areas.)

Leaf-tailed Gecko, Orraya occultus, from a boulder-strewn creek line in NE Qld

Layered rocky areas are well-buffered from fire and provide cool, moist, stable conditions. These conditions are similar to those found in rainforests.

Black Mountain near Cooktown- typical boulder habitat

The Australian continent was once blanketed with extensive rainforests but as conditions became increasingly arid, these forests contracted to smaller pockets like the remnants now found in coastal Queensland and NSW. As the forests contacted so did their faunas and some rainforest animals retreated to, and survived in, rocky landscapes, many of which are now well isolated from modern rainforests.

During this time, many species became extinct but others survived in these rocky landscapes and produced new species. Recent DNA studies show that many of these rock-dwellers have strong genetic ties to modern rainforest animals. The lithorefugia story is important for understanding the evolutionary processes that shaped Australia’s rainforests and their associated faunas.

There are many examples of rainforest animals that survived in rocky areas. Rainforest snail, spiders, tail-less whip scorpions, and microhylid frogs, such as the Black Mountain Boulder Frog are some examples. There are even mammals that have undergone a shift from rainforest to rock. For instance, the Rock Ringtail Possum that is found in rocky parts of the Kimberley region (WA) and Arnhem Land (NT) has genetic and behavioural characteristics similar to the Green Ringtail Possum, a species now found only in the high altitude rainforests of NE Queensland.

Black Mountain Boulder Frog, Cophixalus saxatilis

The above discussion is relevant to Unit 2 (Change and Survival) of the draft Senior Biology Curriculum. For example, in the Science Understanding strand of this unit is the topic: Evolution of Australian flora and fauna, including

  • significant events in Australia’s geological history and their effect on the evolution of a unique flora and fauna
  • the effect of change in past climates on Australia’s flora and fauna

Species adapt to different conditions as habitats and climates change. To learn more about how climate change has affected the evolution of different animal groups, investigate the online learning resource, Dinosaurs, Climate Change and Biodiversity which contains many teacher and student resources.

To learn more about the work that Patrick does, visit his Biography page.

You can investigate leaf-tailed geckos and other amazing reptiles, by visiting the Reptile section on Queensland Museum’s website.

Sea Spiders – from the South Pole to the Tropics

Dr Claudia Arango, a research fellow at Queensland Museum, is one of the few world specialists on pycnogonids (or sea spiders). She has been working on Australian fauna since 1998.

Dr Claudia Arango

Claudia studies these spiders to work out how they evolved; their ecology; relationships among the families and species; and to help understand their position in the arthropod Tree of Life.

Claudia is currently leading a three-year project with an international team of researchers studying the diversification and evolutionary history of sea spiders in Antarctica. She is interested in the connections Australasian species have to Antarctic and deep-sea species.

Antarctic sea spiders tend to be bigger, more abundant, and more diverse than their relatives from warmer locations, particularly the tropics.

The image below shows representative species from four different lineages of sea spiders (Pycnogonida). Nymphon unguiculatum (top left) and Decolopoda australis (top right), a spectacular ten-legged form, both from Antarctica. Endeis mollis is a common tropical species, here feeding on corals from the Great Barrier Reef (bottom left), and Eurycyde raphiaster mostly found in shallow tropical waters from the Caribbean to the Indo-Pacific (bottom right).

In her research, Claudia and her colleagues have found certain ‘hot spots’ of biodiversity in benthic organisms in the icy deep Antarctic waters. They are determining baseline measures so future studies can determine the effects of climate change on existing species abundance and distribution.

Sea spiders feed on a variety of sessile organisms, (or ones that are fixed in one place), particularly bryozoans, which are known to be very susceptible to climate change.

What will be the effect of ice melting and other climate changes on sea floor communities?

To learn more about Claudia’s research visit her Biography Page.