Call of the thylacine

Eleven thousand miles from Wisconsin, this national park is a vast area of wetlands, woodlands and rock formations that is home to a fantastic array of wildlife. Kakadu, one of Unesco’s World Heritage sites, has almost 300 bird species (over a third of Australia’s birds), more than 60 mammals and over 120 reptiles, including large saltwater crocodiles, monitor lizards and snakes.

In addition to seeing some of its dangerous residents, I am hoping to rediscover the image of a magnificent marsupial, the thylacine, that I first saw on a visit more than 20 years ago. The image is still etched in my memory – not because I saw it in the flesh, but because it was painted on a rock. You see, the species went extinct on the Australian mainland about 3,000 years ago. The rock painting, at one of more than 5,000 art sites in Kakadu, must have been made by an Aborigine hunter-gatherer about that time, preserving for posterity the image of an animal now long gone from Kakadu.  

Powerful presence
Weighing about 60 pounds and bearing powerful jaws, the thylacine had a doglike skull, was about the height and shape of a Doberman and had tigerlike stripes on its back that may have helped conceal it in the bush from its prey. Studies of thylacine skeletons suggest that it was a solitary ambush predator like a tiger, and not a pack hunter like a wolf. Even after extinction on the mainland, thousands of thylacines were still roaming the island of Tasmania when European settlers arrived in the 19th century.

The fate of the Tasmanian thylacines is all too familiar. Despite scant evidence of any real threat to livestock, the settlers placed bounties on thylacines and their pups and hunted their natural prey. In 130 years, the combined pressures led to the disappearance of the thylacine in the wild. The last thylacine died in the Hobart Zoo in 1936. I want to find that Kakadu thylacine again.

The drive from Darwin to Kakadu is one of my favourite stretches of road anywhere. It offered great wildlife spotting as we entered the wetlands of this tropical region. This part of the Northern Territory can receive many feet of rain in the monsoon season, from December to March, filling rivers, billabongs and great floodplains that nourish vast bird and fish populations. In some spots, the water appears to be boiling with small fish, which are feasted upon by egrets, jabirus and hawks. In trees nearby, 30 or more sulfur-crested cockatoos are raising a ruckus.

After entering the park, we crossed our first big river. On the east bank, we saw two large saltwater crocodiles sunning themselves. The river is named the South Alligator because that’s what an early explorer thought these creatures were. Big mistake. The crocs are larger and much more dangerous than American alligators.

Many of Kakadu’s mammal and reptile residents are nocturnal, so some of the best action unfolds after dark. As dusk fell on our first day in Kakadu, my headlights picked up the reflection of a snake on the road. Approaching very carefully, I saw from its spotted pattern and head that it was a young Children’s python, about 30 inches long. While Australia is notorious for its many species of venomous snakes, this was not one of them.

The 20 species of pythons can get much bigger; on previous visits I have seen pythons pushing 10 feet. A hike the next day to the Nourlangie art site did not turn up any thylacines, but park rangers calmly pointed out a small snake curled up near one beautifully painted rock face. I recognised the striped camouflage of the death adder – a name that would not inspire comfort among other onlookers.

The second night, we saw another small Children’s python, a few very small legless lizards – and, to my dismay, cane toads by the dozens.This species is not native to Australia. It was brought to Queensland in 1935 to control a pest called the cane beetle.

Not only was the measure an abject failure, the introduction of this prolific and hardy invasive species has been an ecological catastrophe.Throughout their life cycle, the toads produce potent toxins that are fatal to most mammals, snakes and lizards. The toads have advanced across northern Australia at a rate of about 15 miles per year and reached Kakadu’s southern boundary in 2000-2001.

Poor fire management
When I visited six years ago, I saw nowhere near as many toads. And my worry was compounded when I failed to spot two species that were once common here: the large monitor lizard called the goanna and a small, spotted carnivorous marsupial, the quoll. My fears were confirmed when I met with Michelle Ibbett, an Australian mammal expert. Ibbett explained that Kakadu’s mammals have been severely stressed, not just by the arrival of the toads, but also by questionable fire-management practices.

While the aboriginal residents of Kakadu used patchwork burning to clear space and to reduce the risk of major fires, large parts of the park are now being burned deliberately and repeatedly without adequate consideration of the effects on wildlife. And because the goanna population has been decimated by toads, the many burrows they would normally dig are not available to serve as refuge for other species – snakes, lizards and mammals. A recent study by John Woinarski and colleagues at Charles Darwin University in the Northern Territory revealed a very recent, rapid and severe decline of native mammals in Kakadu.

The biologists surveyed 25 species in more than 130 plots over 13 years. They observed that the number of species declined by 54 per cent per plot, and the number of animals by 71 per cent. Moreover, plots with no mammals at all increased to 55 per cent in 2009, from 13 per cent in 1996. Of 19 native species recorded from multiple plots, 10 showed declines and none showed any increase. Several are on the road to extinction. Scientists said the small-mammal populations of Kakadu were in “collapse,” and they placed the blame largely on cane toads and fire-control practices.

In a large conservation reserve, such a collapse is nothing less than a catastrophe. On our last full day in Kakadu, we hiked around the sandstone formations of the Ubirr region and visited the art sites in northern end of the park.

There, on the west face of a great gallery, about 30 feet off the ground, I finally spotted that image of the thylacine I had first seen long ago, created in about 12 BC (before cane toads). I now see the image on the rock not as a cultural relic but as a warning call. It was a few thousand years after that painting was made at Ubirr that a naturalist, David Fleay, entered the zoo enclosure in Hobart to film a male thylacine.

He did not know that his 62-second black-and-white film would be the final, poignant record of the last thylacine to walk the planet. But that thylacine made perhaps the most fitting gesture off-camera, one that served as its own final commentary on the entire history of human-thylacine relations and on our failure to act in time to save the species.

The carnivore then bit him squarely on the buttocks. Kakadu was until very recently thought to be immune from the extinctions that have plagued much of Australia’s native fauna.