During recent roading work, the Brynderwyns were discovered to be an important habitat for New Zealand's highly endangered Hochstetter's frog. Photo / Aaron Thompson, Auckland Council.
During recent roading work, the Brynderwyns were discovered to be an important habitat for New Zealand's highly endangered Hochstetter's frog. Photo / Aaron Thompson, Auckland Council.
A frog expert has called the discovery of 600 native Hochstetter’s frogs during the Brynderwyn Hills’ roading project “remarkable” and says it shows the area must be a significant habitat for the species.
The Advocate was told about the huge number of frogs during a recent media tour of the project site.
Neither the New Zealand Transport Agency Waka Kotahi (NZTA) nor the Department of Conservation (DoC) will confirm the number of frogs found, as both say they are waiting on a formal report process.
However, the Advocate understands that site works destroyed the frogs’ habitat and they were relocated out of the alignment area but further along the same water course.
NZTA director of regional relationships Steve Mutton said the agency had been working closely with DoC to minimise adverse affects on the frogs and other resident taonga species.
A field ecology team was monitoring those species within the site and relocating wildlife as necessary within the requirements of the Wildlife Act.
He said culvert extensions required the removal of habit. A project ecology team manually searched impacted gullies and any Hochstetter’s frogs found were relocated to areas outside the works’ footprint along the same water course that they already inhabit as per DoC approved management plans.
“Salvage” to date had also included snail and lizard species. A sniffer dog was on site to look for kiwi but hadn’t found any so far.
Certified Conservation Dog Handler Steve McManus with kiwi sniffer dog Pearl, who's tasked with locating kiwi that might be at risk from roading work being done in the Brynderwyns. Photo / Supplied
The agency wouldn’t confirm the numbers of each species that had been relocated so far. Figures would not be released until after it had prepared and presented a report to mana whenua and DoC.
DoC also declined to comment on numbers of species relocated saying it was awaiting the report.
Transport Minister Simeon Brown addresses media during a site visit of the Brynderwyn Hills' roading resilience project. Photo / Michael Cunningham
According to the New Zealand Herpetological Society’s website, the Hochstetter’s frog is New Zealand’s most widespread and commonly encountered native frog species.
While classified as at risk - declining due to a multitude of threats, they have fared much better than other native frogs because of their more aquatic nature. They are almost exclusively associated with small forested catchments or seepages.
However, the society said like all frogs, Hochstetter’s were highly sensitive to environmental changes including those caused by infrastructure projects such as the work being done in the Brynderwyn Hills - involving earth movement, habitat destruction, and potential contamination of waterways.
Herpetologist (amphibian and reptile specialist) and Otago University ecology lecturer Jo Monks said to find 600 Hochstetter’s within a single development was “pretty remarkable” as the species, now confined to the north of the North Island, “isn’t doing super well overall”.
It was difficult to say if the relocation of the frogs would be a success as there was not much known about the effectiveness of relocating frogs and amphibians.
Monks said that unless a really thorough survey is carried out as to where frogs are being relocated to then they may potentially compete with resident individuals in the new location.
“And if there aren’t any resident frogs in this case at that new location it kind of suggests that perhaps that environment isn’t quite as suitable for whatever reason.
“So unless there’s other mitigation measures put in place to compensate for that then you can’t really expect them to do as well in the new spot. "
Monks didn’t know how much work had gone into a Brynderwyn Hills’ survey - and neither NZTA nor DoC would disclose the process to the Advocate at this stage.
However, Monks thought it would take at least a week of night-time surveys or day- time rock-lifting surveys - in good weather for frogs.
NZTA says an enormous amount of planning went into assessing and preparing to manage environmental risks before earthworks could begin in the ecologically sensitive Brynderwyn Hills. Photo / NZTA
She said this discovery showed the importance of ecological survey work ahead of major infrastructure projects.
Monks said she had strong concerns about the Government’s proposed suite of legislative changes, including how its fast-track approvals bill, might affect necessary surveys ahead of similar works in future.
