Australia
Millennia of geographic seclusion has fostered species found nowhere else on Earth.
The continent of Australasia can mean different things to different people. What is agreed is that it’s part of the geographical region of Oceania, but the focus of the Australia episode in Seven Worlds is the island continent itself – the mainland of Australia, the smallest of the traditional seven continents.
Australia is the lowest, flattest and driest permanently inhabited continent. About 70 per cent of the land is desert or semi-desert, mainly in the centre and to the west, but there are tropical rainforests in the northeast, including the Daintree forest, one of the oldest on Earth, and snow-capped mountains in the southeast – the Australian Alps. Soils generally tend to be nutrient poor and relatively unproductive, yet the island is biodiversity rich. Many species are found nowhere else on the planet, due in part to Australia’s isolation.
Most of Australia’s native mammals are pouched marsupials or egg-laying monotremes, and the arid conditions favour reptiles, with 755 known species, including five of the most venomous snakes in the world. It means Australia has the most reptile species of any continent.
Realm of the reptiles
The biggest reptile is the saltwater crocodile or ‘saltie’, but the film crew were more interested in its smaller cousin, the freshwater crocodile, known locally as the ‘freshie’. It’s no longer than 4m, with a more slender snout and smaller teeth than its man-eating relative, and one
Little red flying foxes cope with Australia’s scorching heat by quenching their thirst in the Roper River but it’s a risky business, lurking beneath the surface are crocodiles in search of an easy meal.
population is known to migrate to the Roper River in the Northern Territory, where food literally drops out of the sky.
During the dry season here, animals struggle with the intense heat – up to 46°C in the shade – and a drought that can sometimes last for six or seven months. At the Roper River, however, underground springs ensure there’s usually water, and visiting to slake their thirst are thousands of little red flying foxes. When they reach the river, they swoop down and soak the fur on their chests, and then lap off the water when they return to their roost – that is, if they make it back.
Between a croc and a hard place
Waiting just below the surface of the river are the freshwater crocodiles. When a bat drops down, the crocodile surges out of the water, its jaws snapping shut in the blink of an eye. The bats, however, are skilled flyers, and the crocs are not that good at catching them. So why would the bats want to risk death? And why do the crocodiles bother?
Wildlife cameraman John Shier was there watching them.
“The thing that hits you is the angry heat, and it dawns on you just how difficult it must be for bats to handle it, and it starts to make sense that they would want to take such a risk to obtain water,” says John.
“There are about 200,000 bats where we were filming, so the odds of any single bat being taken by a croc aren’t that great, probably no more than 10 in a morning. Then, you wonder why so many freshwater crocs travel to this small backwater and wait every day for a chance to grab a meal.
The key, I think, is how well adapted the crocs are to a sparse and intermittent diet. Like many animals in Australia, crocodiles excel at expending as little energy as possible, so if a croc can catch a bat every few days, it’s worth the time and effort to come here and hunt every day for a month.”
Away from the dry heat of the Outback, the Wet Tropics rainforest in Queensland is the oldest continually surviving tropical rainforest on the planet. At one time Australia was more humid than it is today and tropical forests dominated. When the climate changed, only a few of these forests survived.
Prehistoric plants
One of these is Daintree, a refuge for plants and animals with an ancient past. Growing here, for example, is the idiot fruit tree – known as Australia’s ‘green dinosaur’ – whose ancestors were here 120 million years ago.
The forest itself grows right down to the sea and, walking along the beach, you might be surprised to see dinosaur footprints in the sand. In reality, a large flightless bird made them – the cassowary, sometimes described as
Queensland’s velociraptor, due to its habit of kicking out at enemies and disembowelling them with the large dagger-like claw on its middle toe.
Seven World’s interest in this enigmatic bird, however, was the way in which the father rears the chicks. Finding a father, however, was not that easy. Camera-traps were put out to locate a known individual, but the Australian film crew with permission to enter the forest was unprepared for what they found.
They discovered feral pigs the size of small ponies. It was an animal that should not have been in such an ecologically sensitive area. They churn up the forest floor, destroy native trees and, when it rains, their foraging activity causes flash flood, mudslides and landslides. It was yet another example of how little we know of what goes on in such hidden habitats as tropical rainforests.
“The thing that hits you is the angry heat – it starts to make sense that the bats would want to take such a risk to obtain water.”