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Hochstetter's frogs population

22 July 2022

Hochstetter’s frogs (Leiopelma hochstetteri) are one of four endemic frog species in New Zealand, with fragmented populations found in the North Island, and a conservation status of At Risk - Declining. Our native frogs are somewhat more cryptic than the introduced frogs such as Green and Golden bell frogs (Ranoidea aurea) that can be heard and seen in wetlands and ponds in the North Island, meaning you are unlikely to come across one unless you know where (and how) to look!

Pepeketua (or peketua), New Zealand’s remaining four species of endemic frogs, belong to an extremely ancient lineage. They resemble very ancient frog fossils from the Jurassic era more closely than any other living frog; for instance, they have nine vertebrae while modern frogs have eight, and they land from a jump by 'belly flopping' rather than landing with their front legs. The Hochstetter’s Frog is unusual for the genus Leiopelma, in being semi-aquatic, and in having larvae that hatch from the egg with tails rather than as fully-formed froglets. Ecoquest, 2022

Every three years the Hochstetter’s frog population at Maungatautari is monitored by the team at Ecoquest and their students. The survey is split into two survey periods with 45 transects divided between each period and the same sites surveyed to be able to compare results over the years. After the wonderful discovery of Hochstetter’s frogs at Maungatautari in 2004, these surveys have occurred since 2009 and provide important information on population recovery in the absence of mammalian predators. To date, SMM is the only pest-free (other than mice) sanctuary to contain Hochstetter’s frogs. Unfortunately, over the past two years Ecoquest’s international students were unable to come to NZ under Covid19 restrictions. In 2021 SMM supported Ecoquest by providing staff and volunteers, as well as gaining support from the NZ Department of Conservation (DOC) regional staff to complete the first survey in early May, but unfortunately another Covid lockdown saw the eventual cancellation of the November survey. This meant we needed to repeat the initial survey again this year!

Led by Ecoquest’s David Clarke, staff and volunteers headed out over 5 days in early May. This involved some serious hiking to many of the sites, followed by methodical searching of stream edges and ‘islands’ for frogs in 20 metre transects. Each transect is graded on its suitability as frog habitat before searching for frogs. But how do you find the frogs? Lift rocks! Each rock or cover object is counted (and sometimes reached the hundreds!) and if a frog is detected they are photographed, measured and their housing carefully replaced before moving on. None of the frogs are touched during the process so unwanted pathogens are not transferred and there is no harm to the delicate skin.

The survey this year detected 66 frogs compared to 75 last year, which is likely a reflection of normal variation in detection rather than a decline, but is already a good count compared to the total of 55 frogs found over both survey periods in 2018! The follow up survey and therefore total count and analysis is due in November 2022.

Thanks to the many volunteers that helped to make this survey another great success and to the great teamwork by Ecoquest and Sanctuary Mountain Maungatautari.

Read more in the 2017 research report on monitoring the Maungatautari frog population.

Janelle Ward, Biodiversity Team Leader, Kaiwhakahaere houropi