Rare frogs jump in numbers at Auckland Regional Park

Hochstetter’s frogs in the Hunua Ranges are jumping for joy in an area where an intensive pest control programme knocked off most of their enemies.

A wildlife survey carried out recently on behalf of the Auckland Regional Council and the Department of Conservation shows that the endangered Hochstetter’s frog population is booming in the Kokako Management Area where possum, goat, rodent and stoat populations have been almost eradicated.

Hochstetter’s frogs are one of four New Zealand native frog species, and one of only two still found on the mainland. The frogs are unique – they are nocturnal, have no external eardrum, and their young develop almost fully inside the egg so that they don’t have a tadpole stage as overseas species do. The Hunua Ranges and Waitakere Ranges Regional Parks support most of the Hochstetter populations in the Auckland mainland region.

“It’s very encouraging for all the scientists and volunteers who’ve worked so hard to pull these little guys back from the brink of extinction,” says Bill Burrill, chair of the ARC Parks and Heritage Committee.

The survey shows an abundance of juvenile and young adult frogs, which indicates a relatively rapid rate of breeding. The proportion of young to old had risen significantly since similar surveys were carried out in the mid-90s.

“Hochstetter’s frogs are very fussy about where they’ll breed,” says Cr Burrill. “Only pristine conditions will do. So their increasing number is a good indicator of environmental health – and a sign that we are managing the park’s ecology properly.”

The survey prompted a sigh of relief from biologists, worried that the arrival in 2000 of the deadly Chytrid fungus disease that has devastated the world’s frog populations may have affected the Hochstetter’s frog. Instead, the survey showed that the population structure and health of frogs in the Hunua Ranges is better than other North Island enclaves.

“Building a substantial breeding base is imperative if the species is to withstand Chytrid fungus if it gets into their territory,” says Cr Burrill.

He supports continued monitoring of the frog population. “The lessons we learn here in the Hunua Ranges and Waitakere Ranges Regional Parks are going to be invaluable for managing our precious natural resources in Regional Parks and developing Hochstetter’s frog populations elsewhere.”

Hochstetter’s frogs are fully protected by law and if found shouldn’t be handled.

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