Zealandia Te Māra a Tāne has released a captive population of rare pepeketua/Hamilton’s frogs into the wild at the ecosanctuary. This marks a major milestone for the not-for-profit and for the conservation of the species in Aotearoa New Zealand.

Hamilton’s frog is considered a Nationally Critical threatened species, and there are no other wild populations on mainland New Zealand as they are heavily impacted by habitat loss, disease and predation.  

Jo Ledington, Zealandia’s General Manager Conservation and Restoration, reflects on this milestone.

“Zealandia is the only place on the mainland where Hamilton’s frogs are living in the wild. This means, outside of remote offshore islands, there is nowhere else people can see them in the wild.”

The last of the captive population was released from their enclosure following the opening of a new boardwalk that was built to protect them from human foot traffic. This boardwalk was made possible through a generous gift from the estate of John Nankervis.

The decision to release these frogs was made in collaboration with the Department of Conservation Frog Recovery group and with the support of kaitiaki Ngāti Kuia and Taranaki Whānui ki Te Upoko o Te Ika. It has taken 20 years of monitoring and research of the population to come to this decision.

The population at Zealandia has been essential for research into this highly threatened species, and this research is what led to the decision to release the frogs.

“The release of pepeketua really shows the value of our long-term research into the conservation of New Zealand’s most endangered species. This research showed us the species can survive in the presence of kiwi and mice and is critical information 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,” says Ledington.

“As Zealandia’s world-first fence turns twenty-five, this milestone is one of the many great examples of what has been achieved for conservation since Zealandia’s conception. I’m excited to imagine where we could be in another 25 years with the support of our incredible community and partners.”

The tiny pepeketua/Hamilton’s frog (now considered the same species as Maud Island frog) are one of three native frog species in Aotearoa and are one of the world’s most endangered frogs. Frogs are incredibly sensitive to disease, pollution and environmental disruption due to their sensitive skin. Introduced mammalian predators also pose a big 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. These tiny frogs were released into three fully enclosed pens (a display pen near a walking track and two larger off-track pens), as it wasn’t known at the time how the frogs 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 the frogs from kiwi. This was to assess how they would do in the presence of mice while still protecting them from kiwi. Some frogs dispersed beyond this fence, and surveys have shown they are doing well in the presence of kiwi and mice.

Surveys carried out at Zealandia over the last few years have found frogs of a variety of sizes including pregnant females and young froglets in both the captive and wild populations which shows that the population is doing well. In addition, some frogs were found a distance from their original area, indicating that some of the population was spreading out throughout the sanctuary – incredible for a species with a tiny home range.

To enable the frog population to live in the wild at Zealandia, a new boardwalk was constructed for Zealandia visitors, designed to prevent frogs climbing on it. This is to keep them safe from people walking in the sanctuary at night, as the frogs are very small and well camouflaged, and they do not croak. Zealandia is extremely grateful to John Nankervis’s Estate for the generous financial support of building this boardwalk.

“This milestone would not be possible without the generosity of people such as John Nankervis and the executors of his estate, Jim Lynch and Dave Bamford,” says Ledington.

The newly released population of Hamilton’s frogs will continue to be monitored by Zealandia Te Māra a Tāne as they disperse.

Only minutes from the centre of the city, the award-winning Zealandia sanctuary also provides visitors the opportunity to get up close with other rare and endangered taonga (treasures) living wild, who are normally found on remote, offshore islands. The best chance to see a nocturnal Hamilton’s frog at Zealandia is on a Zealandia by Night tour.

Notes:

• John Nankervis was a prominent mountaineer and conservationist who grew up in Karori. A gift from his estate paid for the valuable boardwalk which protects Zealandia’s pepeketua/Hamilton’s frogs. Zealandia is very grateful for support of this type for conservation work.
• Zealandia Te Māra a Tāne is the world’s first fully fenced urban ecosanctuary, with an extraordinary 500-year vision to restore a Wellington valley’s forest and freshwater ecosystems as closely as possible to their pre-human state.
• All the proceeds from tours go right back into the conservation work. Every visitor that comes to Zealandia not only gets to experience seeing rare species but is also directly contributing to the work that is happening to save and protect them.
• New Zealand native frogs don’t have vocal sacks, and therefore don’t croak regularly (they can still make tiny chirps when alarmed).
• Hamilton’s frogs live amongst rock piles and leaf litter so have almost no webbing on their feet.
• They don’t have a tadpole stage, preferring instead to lay eggs in the ground or trees. The males guard these eggs for several months until froglets hatch. They then carry them around on their backs until the froglets are fully developed.
• Frog body size is generally measured as snout to vent length (SVL). SVL is the distance from their snout (tip of their nose) to their vent (bottom). Male Hamilton’s frogs are the smaller of the two sexes with a SVL <43 mm, females can be slightly larger with SVL<52 mm.
• Video can be found here: https://www.dropbox.com/scl/fo/j652u10x99y67tokfl4ll/AI3W5psEXQ8Y5B_4CLExxL8?rlkey=0e5c65fijml6qusfovtijtp01&st=qtl8z0yc&dl=0

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