NSW was down to one male spotted tree frog. Now they’re back, writes James Woodford.
It is pitch black and we are up to our shins in the frigid waters of Bogong Creek in Kosciuszko National Park at an altitude of 1100 metres.
Amid the splashing of rapids Dr Dave Hunter, a threatened species officer with the Department of Environment and Climate Change, and Mike McFadden, a herpetologist at Taronga Zoo, are looking for sparkles the size of dewdrops. From the thick, tall forest of alpine ash beside the creek there is the call of an endangered yellow-bellied glider. Conversation is hard above the constant rush of water over boulders, following a summer of good rain.
Caught by the glow of our torches, a native fish called mountain galaxids can be seen swimming around crystal-clear pools. “An abundance of mountain galaxids indicates an absence of trout,” Hunter says.
Trout are an enemy of frogs and native fish. The fact that the exotic fish – known to many scientists as foxes of the water – are not here is what helps to make Bogong Creek such a special place.
The rocks in the waterway are slippery and wild undergrowth makes the banks impenetrable.
“I’ve got one,” says McFadden.
It is amazing that Hunter and McFadden saw these two pinpoints of light reflected in their small spotlights and even more incredible that they are there at all.
The pinpoints are the eyes of a spotted tree frog, perhaps the most endangered animal in New South Wales. Just a decade ago the species was represented in this creek by a lone male – the last survivor of an amphibian apocalypse. So dire were the prospects of the spotted tree frog in Bogong Creek that in 1998 the decision was taken to catch the last male and bring him into captivity at the Amphibian Research Centre near Melbourne, under the care of the centre’s director, Gerry Marantelli. There the frog was mated with captured females from an endangered Victorian population at Wheeler Creek.
In spite of the desperate situation of that last male he was given the nickname Dirk Diggler, after the mythical porn star. Instead of Roller Girl, Dirk’s partners are known as the Wheeler Girls.
Luckily both parties have lived up to their names.
“Dirk has got a lot to be proud of,” McFadden says.
In the last two years the NSW Department of Environment and Climate Change and the Amphibian Research Centre in Melbourne have been able to release 600 of Dirk’s offspring as year-old frogs.
Every few weeks over summer a party walks up the exact same stretch, following the same survey methods. The work is far removed from simply emptying a bucket of tadpoles back into Bogong Creek – strict protocols have been written and everything is done according to rigorous scientific rules.
Spotted tree frogs were discovered by accident in NSW in 1973 when Dr Hal Cogger, of the Australian Museum, stopped his car by Bogong Creek and found them basking in the sun. At that time the area was thick with the amphibians and catching them was easy.
Among herpetologists the find was a sensation and studies of the population were undertaken. But almost as soon as monitoring was started, the frog population declined disastrously. Scientists started to find sick and dying frogs but no one knew the cause of the catastrophe.
Hunter says it now seems almost certain that a fungus called chytrid is killing and infecting frogs worldwide. It is also now thought that humans may play a part in the spread of the pathogen. The population collapse is of particular concern to Hunter as he was part of those early surveys when he was an undergraduate.
HUNTER points to where he and McFadden have found the spotted tree frog. The creature is on a steep, downstream face of a boulder. But I cannot see anything.
The frogs are well camouflaged and amid the chaos of the wilderness stream the only way of finding them at night is by catching their reflected eyeshine. We move closer and it is not until the frog is almost close enough to touch that its body becomes visible.
Hunter gloves up to make sure there is no risk of spreading any kind of infection. He catches it and stretches out its toes. Because these captive-reared frogs are virtually identical to each other, scientists clip their toe joints so they can follow the life history of each released animal. The absence of a digit on the frog’s feet correlates to a code which allows each specimen to be numbered.
“He is individual 1088,” Hunter says. “He was released as a year-old animal in January ’07. Now we are going to process him.”
Frog 1088 weighs in at a wispy 4.18 grams and is measured before his toes, fingers, armpits and groin are swabbed. The swab sample will be sent to the CSIRO Animal Health Laboratory in Geelong to determine if he is infected with the chytrid fungus.
Their fear is that sending captive-bred frogs into the wild is like ordering soldiers out of a trench in front of an enemy machine gun post.
For endangered amphibians the captive breeding is just the first challenge. Sometimes very large aquarium populations can be established quickly. And that seems to be the case with the spotted tree frogs. A captive-breeding program, however, can only buy time. Eventually a species has to go out and face the worst Mother Nature can throw at it.
The spotted tree frog project is one of the few in the world where the early results have been so promising, Hunter says. “We are excited about this project because, so far, it has worked.”
By the end of the evening Hunter and McFadden have found eight young frogs. It is nearly 11 pm by the time the scientists reach the end of the survey. As we clamber up the bank and onto the first clear, level land we have seen since dusk, McFadden says: “You have just seen a species that was extinct in NSW.”