Hamilton's frogs are one of the world's most endangered frog species. Photo: Hayley May
An Wellington ecosanctuary has released a captive population of rare pepeketua into the wild.
Hamilton's frogs are one of three native frog species in New Zealand, and one of the world's most endangered.
Considered nationally critical - the most severely threatened species - there are no other wild populations on the mainland as the frogs are heavily impacted by habitat loss, disease and predation.
After 20 years of monitoring and research, the last of the captive population were released last week from their enclosure at Zealandia following the opening of a boardwalk built to protect them from human foot traffic.
The boardwalk was designed to prevent the frogs - which were very small, well-camouflaged and do not croak - from climbing on it.
The decision was made in collaboration with the Department of Conservation frog recovery group and kaitiaki Ngāti Kuia and Taranaki Whānui ki Te Upoko o Te Ika.
Zealandia general manager of conservation and restoration Jo Ledington said research had showed the species could survive in the presence of kiwi and mice, which was critical knowledge for the establishment of future populations.
"Now, with the species fully wild, we can also explore complex questions that will have further implications for the conservation of this species at a national level."
Due to their sensitive skin, frogs were incredibly prone to disease, pollution and environmental disruption.
Introduced mammalian predators also posed a serious threat to these endangered species.
Hamilton's frogs from Te Pākeka/Maud Island and a captive population at Canterbury University were translocated to Zealandia in 2005. They were released into three fully enclosed pens as it was not known at the time how they would fare with the kiwi and low levels of mice present in the sanctuary.
In 2012, a further 100 frogs were released within an internal fence that protected them from kiwi to assess how they would do in the presence of mice while still protecting them from the native birds.
Some frogs dispersed beyond this fence, and surveys had shown they were doing well in the presence of kiwi and mice.
Surveys carried out at Zealandia over the last few years had found frogs of a variety of sizes - including pregnant females and young froglets in both the captive and wild populations, which showed the population was doing well.
The newly released population of pepeketua would continue to be monitored by Zealandia as they dispersed.
