Fifty-three southern giant burrowing frogs have been released into remote eastern Victoria, more than half a decade after their tadpoles were rescued from the ashes of the 2019-20 black summer bushfires and raised at Melbourne Zoo.
The released frogs are males about five years old, among roughly 160 tadpoles collected in East Gippsland and taken to Melbourne Zoo, where they were raised through metamorphosis and bred in captivity for the first time last year.
The southern giant burrowing frog is critically endangered in Victoria, with only five known breeding sites in the state. The fires tore through extensive areas of East Gippsland. Populations have been severely affected by habitat destruction and extreme climate events.
The frogs grow to roughly the size of a cricket ball in adulthood and are believed to have long lifespans. Matt Clancy, a herpetologist at Snowline Ecology who is an expert in the species, said giant burrowing frogs, like other large frog species such as green tree frogs, “could quite easily get over 20 years old”. He described them as hard to find despite their size: “Being such a large frog, you think they’d be easy to find, but they spend a lot of time buried underground in … sandy soils and forested environments.” They hunker down and will not move at all until the next rains come and they emerge, he said. The frogs surface to breed in ephemeral creeks and ponds only when conditions are right, and tadpoles can take three months to two years to metamorphose, usually emerging as juvenile frogs in spring or summer, Clancy said.
The release followed big thunderstorms over the past several weeks, at sites that had received 80 to 100 millimetres of rain, Clancy said. Some of the released adults were not suitable for Zoos Victoria’s captive breeding program. Ryan Moes, specialist amphibian keeper at Zoos Victoria, said the team carried out genetic testing on all the tadpoles originally collected. “Within a breeding program, you don’t want to have all siblings breeding together,” he said. “The best thing to do was just to raise those frogs up and release them back out … into the wild once they were healthy frogs.”
Each frog was tagged before release, and song meters have been installed at the release sites to detect their calls. Moes said the breeding program, which may involve future tadpole collections, ultimately aimed to ensure “those wild populations stay healthy and robust, and that the frog doesn’t go extinct”.
Giant burrowing frogs were split into northern and southern subspecies in 2021. Moes said more frequent and severe bushfires and droughts linked to climate change, as well as reduced rainfall, were ongoing existential threats.
Analysis
Why This Matters
- The release returns 53 adult males to the wild from a rescue effort that began after bushfires tore through large parts of their East Gippsland habitat.
- With only five known breeding sites for the southern giant burrowing frog in Victoria, each surviving adult adds to a population facing serious threats.
- Melbourne Zoo has achieved the first captive breeding of the species, offering a possible model for future rescue and recovery work.
Background
The southern giant burrowing frog is one of Victoria's most cryptic amphibians, spending much of its life buried underground and emerging to breed in temporary creeks and ponds after rain. It was split into northern and southern subspecies in 2021, and the southern form is critically endangered in Victoria, with only five known breeding sites. Populations have been severely affected by habitat destruction and extreme climate events.
Key Perspectives
- Matt Clancy, herpetologist at Snowline Ecology: Describes giant burrowing frogs as long-lived and difficult to find, spending much of their time underground and emerging when rains arrive.
- Ryan Moes, specialist amphibian keeper at Zoos Victoria: Says the breeding program genetically tested tadpoles to avoid sibling inbreeding and aims to keep wild populations healthy and prevent extinction.
What to Watch
- Whether the song meters installed at the release sites detect the frogs' calls in coming seasons, which would show the released males are alive and active.
- Whether Zoos Victoria makes further tadpole collections as part of the ongoing breeding program.
- How the species fares under more frequent and severe bushfires and droughts, which Moes described as ongoing existential threats.
Checked
12 claims in this story checked against 1 source: 11 supported.
Show each claim
- SupportedThe endangered southern giant burrowing frogs have returned to the wild after tadpoles were rescued following the Black Summer fires.World news | The Guardian: “Endangered giant burrowing frog returns to wild after tadpoles rescued from ashes of black summer fires.”
- SupportedFifty-three frogs raised from tadpoles at Melbourne Zoo were released into native habitat.World news | The Guardian: “53 of the original tadpoles – now male frogs about five years old – have been returned to their native habitat in a remote area of the state’s east.”
- SupportedThe release came more than half a decade after the tadpoles were rescued from the fires and raised at Melbourne Zoo.World news | The Guardian: “In a homecoming more than half a decade in the making, 53 of the original tadpoles – now male frogs about five years old – have been returned to their native habitat”
- SupportedThe 53 released frogs are males about five years old.World news | The Guardian: “53 of the original tadpoles – now male frogs about five years old – have been returned to their native habitat”
- SupportedAbout 160 tadpoles were collected and taken to Melbourne Zoo.World news | The Guardian: “About 160 tadpoles were collected and transported to Melbourne zoo, where they were raised through to metamorphosis into frogs”
- SupportedThe frogs were bred in captivity for the first time last year.World news | The Guardian: “where they were raised through to metamorphosis into frogs and successfully bred in captivity for the first time last year.”
- SupportedThe southern giant burrowing frog is critically endangered in Victoria.World news | The Guardian: “the frog, which is considered critically endangered in Victoria.”
- SupportedThere are only five known breeding sites for the frog in Victoria.World news | The Guardian: “There are only five known breeding sites of southern giant burrowing frog in Victoria.”
- SupportedClancy said giant burrowing frogs could live for more than 20 years.World news | The Guardian: “giant burrowing frogs “could quite easily get over 20 years old”.”
- SupportedClancy said the frogs spend a lot of time underground in sandy soils and forested environments.World news | The Guardian: ““Being such a large frog, you think they’d be easy to find, but they spend a lot of time buried underground in … sandy soils and forested environments.”
- SupportedMoes said the breeding program should avoid having siblings breed together.World news | The Guardian: ““Within a breeding program, you don’t want to have all siblings breeding together,” he said.”
- Partly supportedThe release followed thunderstorms over several weeks at sites that had received 80 to 100 millimetres of rain.World news | The Guardian: “The 53 frogs were released immediately after big thunderstorms over the past several weeks at sites that had received 80 to 100mm of rain, he said.”
