BioGecko Issue 2 (October 2014)

Herbert, Sarah; Melzer, Sabine; Gilbert, Judy & Jamieson, Halema 2014. Relative abundance and habitat use of Hochstetter's frog (Leioplema hochstetteri) in Northern Great Barrier Island: a snapshot from 2012. BioGecko, October 2014, 2: 8-11.

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HERBERT, SARAH; MELZER, SABINE; GILBERT, JUDY & JAMIESON, HALEMA

Relative abundance and habitat use of Hochstetter's frog (Leioplema hochstetteri) in Northern Great Barrier Island: a snapshot from 2012.

Abstract: The Hochstetter’s frog (Leiopelma hochstetteri) populations on Great Barrier Island are genetically distinct from mainland populations and represent the only offshore island location for this species. Previous surveys have shown that frogs are widespread throughout forested areas of the northern part of the island, with an additional population near the centre of the island. However, the trend in abundance of these populations is currently unknown. Here, we report on the relative abundance and habitat use of Hochstetter’s frogs encountered during a survey of the headwaters of five catchments in northern Great Barrier Island conducted between November and December 2012. A minimum of 253 individual Hochstetter’s frogs were found within 1.5 km of stream habitat. Both juvenile and adult frogs were encountered. Continued presence of these frogs in four catchments was confirmed, and frogs were detected in a catchment that had not been previously surveyed. Two stream headwaters appeared to yield a lower relative abundance than during a previous survey in 2009. Relative frog abundance was positively correlated with the frequency of waterfalls and boulders, and was lower in sediment-loaded streams that had finer substrates and a kanuka-dominant canopy. Hierarchical cluster analysis of the 13 habitat features that were moderately to strongly correlated with abundance could accurately discriminate transects by both frog abundance and presence of juvenile frogs. This may provide a useful quantitative method for assessing Hochstetter’s frog habitat quality in cases where the number of habitat measures exceeds the number of transects surveyed. A sustained monitoring programme for Hochstetter’s frog abundance in northern Great Barrier Island is recommended to assess the long-term population trend.

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