In a significant conservation milestone, Hamilton’s frogs—one of New Zealand’s three native frog species and among the most endangered globally—have been reintroduced to their natural habitat at Zealandia. This species is critically endangered, with no remaining wild populations on the mainland due to severe threats from habitat destruction, disease, and predation.
Following two decades of dedicated research and monitoring, the last group of these frogs was released from captivity last week. This release coincided with the opening of a newly constructed boardwalk, designed specifically to safeguard the frogs from human disturbances. The boardwalk, which prevents the frogs from climbing onto it, is a crucial measure, as these small, camouflaged frogs do not produce vocal calls.
The release plan was developed in collaboration with the Department of Conservation’s frog recovery group and the kaitiaki Ngāti Kuia and Taranaki Whānui ki Te Upoko o Te Ika. According to Jo Ledington, Zealandia’s general manager of conservation and restoration, research has demonstrated that Hamilton’s frogs can thrive alongside kiwi and mice, a finding that is essential for future conservation efforts.
Ledington noted, “With the species now reintroduced into the wild, we can investigate complex questions about their conservation at a national level.”
Hamilton’s frogs, sensitive to environmental changes due to their delicate skin, are vulnerable to diseases, pollution, and disruptions. The introduction of mammalian predators further endangers their survival.
Since their initial translocation to Zealandia in 2005 from Te Pākeka/Maud Island and a captive population at Canterbury University, the frogs were initially housed in three enclosed pens. This precaution was taken to observe their interactions with kiwi and low mouse populations. By 2012, an additional 100 frogs were released into a fenced area designed to protect them from kiwi while assessing their adaptability to the presence of mice.
Subsequent surveys indicated that some frogs had dispersed beyond the protective fence and were thriving in the presence of both kiwi and mice. Recent evaluations have shown a diverse population, including pregnant females and young froglets, indicating a successful establishment.
The newly released population of Hamilton’s frogs will continue to be monitored by Zealandia as they adapt to their reintroduced environment.