Surprising discovery in remote Aussie creek

Yahoo

3 days ago

It's doubtful many Aussies could find a spotted tree frog in the bush. First of all, there are only around 1,000 adults left in the wild, and then there's the problem that they're no bigger than a matchbox.
Amphibian ecologist Dr Matt West had the difficult task of releasing 275 captive-bred frogs into a Victorian wilderness and then trying to find them again to see if any survived, by looking under rocks, on top of plants, and in the ripples of cold streams. 'They were also well camouflaged, so they're very difficult to find,' he told Yahoo News Australia.
But despite these challenges, the team was "surprised" to find many more than they initially expected were still alive, despite them facing multiple threats.
The spotted tree frog was listed as critically endangered after numbers plummeted due to a series of horrifying events over the last 30 years, including the introduction of deadly chytrid fungus, the spread of introduced fish, and the Black Summer bushfires which wiped out half of its habitat in Victoria. The release of the frogs is designed to help revive populations and boost genetic diversity.
The frogs were bred at Melbourne Zoo, and then set free as juveniles into the Kiewa River system, which snakes through Mount Beauty in northeastern Victoria. Their range naturally stretches from northeastern Victoria into NSW. The work is part of the Spotted Tree Frog Project, a collaboration between West's company Wild Research, Zoos Victoria and Duduroa Dhargal Aboriginal Corporation.
Why researchers initially struggled to find many frogs
There can be a lot of variation in the appearance of spotted tree frogs, depending on their environment. Some are bright green, while others are brown, but all have noticeable bumps on their skin, which is why they're called "spotted" tree frogs.
The frogs were released in February, and researchers then had to work fast and track the frogs before winter set in and they became dormant.
'We were going back every month and spending a week out there at a time searching possible areas for the frogs,' West said.
'Initially, we were looking in a tight, little search area where they were released, and we were worried because we weren't finding many of them.'
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The team then broadened their search area, and were surprised to find many of the frogs had travelled up to 2km. While this was considered 'unusual' for the species, previous surveys have focused on adult animals, and the frogs they released were juveniles.
The difficulties experienced in finding rare frogs
When counting other species of frog, it's common for researchers to track them down by listening for their call. But spotted tree frogs can live for up to 18 years, and don't become sexually mature until around five, so they don't start to call for a mate until then.
Besides, the search was conducted around a noisy creek, which roars so loudly it's nearly impossible to hear much at all. So instead, the specialist team had to look out for their eye shine and body shape.
'It's very tricky to find them, they've got very small eyes, and a very small eye reflection as a result. Unfortunately, there's a lot of other things that reflect in their environment as well, like little flecks of granite, water droplets, and spiders,' West said.
What's the best place to release the frogs?
Because the frogs face multiple threats in the wild, only around one per cent have traditionally survived to adulthood. To minimise their chances of death, the frogs were set free in safe havens.
Many of the best spots were bushfire-affected, with little vegetation, so the sunlight could reach the creeks. That's because warmer regions, where the air temperature soars above 25 degrees, make it difficult for chytrid fungus to survive. Other places were chosen because they were free of introduced species like trout.
Their choices appear to have been successful because, surprisingly, around half of the captive-bred animals were relocated during their search.
To date, 600 frogs have been released as part of the Spotted Tree Frog Project.
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