Habitat suitability and requirements for a threatened New Zealand amphibian

Abstract

Habitat modification is one of the largest threats to global terrestrial biodiversity, yet management tools such as translocations often fail because of insufficient knowledge about species' habitat suitability and requirements in release areas. Resource selection is a useful technique that can address this issue. In 2014, we investigated resource selection of Hochstetter's frogs (Leiopelma hochstetteri) in mature (>30 year) exotic pine (Pinus radiata) plantations and regenerating native broadleaf forests in Torere Forest (Bay of Plenty, North Island), New Zealand, where harvesting of pines threatens this population. We then determined whether key habitats were present at the proposed target translocation site, Orokonui Ecosanctuary (Dunedin, South Island), New Zealand. In Torere Forest, we conducted daytime searches for frogs along streams and recorded microhabitats (e.g., cobbles) in used and random available plots. In Orokonui, we recorded microhabitats in randomly distributed plots because Hochstetters's frogs are presently absent. We used averaged mixed (binomial) models to identify important resources in pine plantations and native forests and to compare resource use between habitats. Finally, we predicted habitat use in Orokonui and Torere Forest to gain an indication of habitat suitability. Frogs predominantly selected cobble microhabitats in pine plantations and native forests but also partially decayed logs ≥15 cm in diameter within pine plantations. In contrast, high gravel cover and sand-silt were avoided by frogs. In response to limited cobble cover in pine plantations, frogs were more generalized in selecting resources (primarily logs) than in native forests. Habitat suitability was slightly lower in pine plantations compared to native forests, but mature pine plantations do provide suitable habitat for Hochstetter's frogs, at least in the short term prior to pine harvesting. Our study suggests that Orokonui provides suitable habitat for the proposed translocation of Hochstetter's frogs. © 2016 The Wildlife Society.