Extinction of Australian Megafauna Flashcards
What is extinction?
The death of all members of a species.
Provide some examples of Australian megafauna.
Diprotodon - large wombat
Megalania - large goanna
Procoptodon - large, flat faced kangaroo
Provide some examples of megafauna from other continents
Woolly mammoth - Europe and North America
Giraffes, hippo, elephant - Africa
What are the three theories about the extinction of Australian megafauna?
Changes in climate associated with ice age
Human arrival
Nutrient levels
What is the most commonly accepted theory about how Australian megafauna became extinct?
A combination of climate changes and the arrival of humans.
Outline the theory that climate changes caused the extinction of Australian megafauna.
The continent dried out due to the ice age. Rainforests contracted due to drying climate, and returned less water to the atmosphere. Less rain. Fires and droughts broke out, killing Australian megafauna who relied on lots of water.
Describe why the contraction of rainforests is crucial to the theory about climate changes.
Prior to the ice age, rainforests stored moisture and returned it to the atmosphere. Monsoon rains would then fill the rivers and lakes in Australia - keeping megafauna alive. These rainforests were replaced by eucalyptus forests that did not store as much water.
Outline arguments that support the theory about climate changes.
Megafauna were dependent on large water supply. They could not manage the sudden change in temp, breeding season affected, plants they ate became less palatable/ available.
Outline arguments that oppose the theory of climate changes.
The last ice age would not have been any different, and would not have caused such a dramatic event.
Earlier extinctions seemed to have peaked before the last ice age.
Climate change today does not select against large species.
When did Aboriginal people arrive in Australia?
65,000 years ago. Island hopped from the north.
Describe the effect of Aboriginal fire-stick farming.
Aboriginals used fire-stick farming to burn back the bush to regenerate grasses and increasing animals to feed on. This changed the habitat from woodland with a nutritious understory to an arid treeless habitat dominated by low nutrient valued plants that were fire and drought tolerant. Less food for megafauna.
Describe the effect of hunting on megafauna populations
Evidence supports that Aboriginals hunted the megafauna, because they were slower. The smaller animals survived and passed on their genes.
Describe how human introduction of non-native species affected the megafauna population
Introduction of the dingo 4000 years ago could have lead to decline in diversity of carnivore predators. Dingoes possibly drive the Thylacine and Tassie devil to extinction on mainland.
Outline arguments that support the theory of human arrival.
Humans were involved in the first increase in fires, with carbon deposits in fossils as evidence. Smaller species of megafauna were slow and had short limbs. The largest surviving present day species are the fastest in Australia (eg. kangaroos)
Outline arguments that oppose the theory of human arrival.
No fossil evidence of kill sites, and little evidence of them co-existing.
There is an overlap between largest living species and smallest extinct species.
