On most nights you’ll find Dr Greg Brown, notebook in hand, walking the abandoned wall at Fogg Dam, a 45-minute drive east of Darwin.
It’s a walk the Macquarie University post-doctoral research fellow has taken more than 4,000 times over the past 22 years.
Into the notebook, Dr Brown is meticulously recording, to the best of his ability, all the animals he sees in the monsoonal floodplains — a landscape host to one of the world’s highest biomass of predator (water pythons) to prey (dusky rats) ratios.
“A lot of the things that I see I just make a note of: there’s a water python, there is a death adder, there is a possum. But the things that I study more in depth, the keel backs [freshwater snakes] and the slaty-grey snakes — if I see one of them, I have to dart after it.”
True to his word, Dr Brown dives onto a pile of leaves and emerges with a snake, as a pair of wild buffalo and a freshwater crocodile watch on from the water.
“When I catch them I take them back to the lab and mark them — little scars on specific scales so I know who each individual is,” Dr Brown says.
“When you get a lot of information from a lot of different snakes, then you can start to get a picture.”
Dr Brown’s interest in herpetology is far from a hobby — eminent biologist and Macquarie University Professor Rick Shine calls the researcher a “freakishly good field worker”.
“He’s been prepared to get out there on the dam wall every evening,” Professor Shine says.
“Night after night, year after year, to give us that really comprehensive data set on exactly what’s happening with fauna of the Top End across the last two decades.”
‘No-one was out counting goannas in the 1920s’
Dr Brown remembers well the first cane toads at Fogg Dam in 2005.
“They were pretty spectacular looking, all of a sudden these giant toads had showed up,” he says.
The huge data set laboured over by Dr Brown, which started before the arrival of the species, is a pioneering first-hand study of the impacts of cane toads on the environment.
“Even though the cane toads had been in Queensland 75 years, a lot of people couldn’t really nail down what impacts they had had on the animals there,” Dr Brown says.
“No-one was out counting goannas and taipans and king brown snakes in the 1920s, so this was really the first opportunity to get some good background data for before and after the toads arrived.”
Research tells a tale of struggle and fightback
The impacts of the toad invasion were immediate, with populations of blue tongues, king brown snakes and goannas devastated.
But 15 years on, there are signs of a resurgence behind the cane toad frontline.
“In the NT there is now evidence that populations of some species are recovering and/or increasing, including freshwater crocodiles, Merten’s water monitors and northern quolls in some locations,” says the NT Government’s director of terrestrial ecosystems, Dr Graeme Gillespie.
“Other species, such as Mitchell’s water monitors and bluetongue lizards, remain rare in areas where toads are established.”
Professor Shine, one of Australia’s leading cane toad researchers, says the pests didn’t have the impact many were expecting.
“The toads don’t have all that much of an ecological impact after they have been around for a while,” he says.
“They’re catastrophic when they first arrive and they kill the goannas and the king browns, but after a while the system comes back to an equilibrium.”
Climate shifts trump toad threat
After two dry Northern Territory wet seasons, there are signs of distress in the Fogg Dam ecosystem.
“The impact of cane toads is dramatic, but only on a few species,” Dr Brown says.
“The impact of two bad dry seasons or intermittent floods, they have wide ranging impacts.
“So, it’s not just one or two species that are affected, it’s a whole community of frogs, which is affecting a whole community of snakes and a partial community of birds.
Dr Brown has Australian Research Council funding for the next five years to study cane toads and their lung worm parasites.
While he works diligently away on that project, Dr Brown says the rest of his reptile research is a labour of love.
“Because I’m here and I’ve got a job studying toads and parasites, I can come here at night and continue looking for snakes and tracking the tropical animals that I see,” he says.
“After looking after toads or analysing data all day, going up to Fogg Dam for an hour at night is relaxation time.”
