Extinction of Recent Megafauna
300,000 years and still going
The extinction of Australian megafauna attracts a good share of public interest and emotions. Discussion often centres around two contrasting scenarios. One explains the demise of large animals via a complex ecology of increasingly dry climate. The other scenario focuses on direct hunt-killing by the Aboriginal ancestors.
The scientific evidence is not simple or easy to interpret and, sometimes, difficult to access. In this short article I look at the megafauna extinction from a different perspective - the past few hundred years.
Firstly the number of animals considered large (mega) of about 50kg and over are still alive. The Red kangaroo, emu, salt water crocodile and goanna are good examples.
The population of Red kangaroos fluctuates - it was estimated to number about 10 million in the 1990s. About 1.1-1.6 million of Red kangaroos are killed for meat each year. The population of three species of large kangaroos – Red, Eastern grey and Western grey – combined, fluctuated over a few decades from about 15 to 50 million in the areas of commercial ‘harvesting’. Kangaroo meat is exported to 55 countries.
It is estimated that up to 1.25 million Aboriginal people lived in pre-colonial Australia – the equivalent of the recent population of Adelaide. This number could include up to a half million active hunters, or one hunter per over 12 square kilometres – which makes it one hunter for several millions of large kangaroos. In this equation the foraging people had no chance to kill off all kangaroos.
Furthermore, the healthy diet – reported in early ethnographic sources – would include great variety of food, predominantly plant (apart from the coastal areas where fish was a significant component). In such ratio of people to land and resources, hunting can be viewed as nibbling rather than raiding an abattoir.
Animals larger than the kangaroo, say Diprotodon, were possibly less numerous and their reproductive strategy may have prevented them from rapid population expansion. But were they such an attractive source of protein for small group of foraging people? A kangaroo or several emu eggs were a generous serve of protein for a large family group. Diprotodon would be far too large and mostly wasted – eaten by predators and scavengers. And Diprotodon lived alongside Aboriginal ancestors for at least 20,000 years – so no rapid-killing scenario.
It is most likely that with prolonged use of fire, people contributed significantly to changing vegetation – reduction of forest and promotion of grassland. This would accelerate the long progressing shift to arid climatic conditions and limit ecological support for browsing animals such as Diprotodon, while promoting habitat for grazing animals such as modern kangaroo species.
In the past two hundred years Australia became home to new megafauna – imported animals which went feral. They include camel (1 million) deer (1 million in Victoria alone) pig (23 million) water-buffalo (150,000) donkey (5 million) horse (300,000) goat (2.5 million). The combined population of these large ‘exotic’ animals is of a magnitude comparable to native large kangaroos. Sustained eradication programs manage, at best, to reduce their population – reduction of water-buffalo was most successful so far. The population of camels doubles every decade. In general ‘ferals’ are expected to stay – we just cannot make them extinct by killing, even with firearms, helicopters, chemicals and biological means, as well as with the ‘army’ of commercial and recreational hunters.
A tentative lesson from this modern experience – it is very hard to make ‘extinct’ common animals by killing, unless you destroy their habitat and change the climatic and ecological conditions beyond what they can tolerate.
Dr Stan Florek , Database Manager