Abundance of Leiopelma archeyi on the Coromandel Peninsula in relation to habitat characteristics and land-use

Abstract

Habitat disturbance is a significant factor contributing to biodiversity decline worldwide. Amphibians are particularly vulnerable because of their specific microclimatic and microhabitat requirements. In Aotearoa New Zealand, Archey’s frogs (Leiopelma archeyi) have shown some degree of resilience to severe habitat disturbance historically. However, it is unknown how much L. archeyi populations are currently being impacted by historical and ongoing mining activities and development within their range. To address this issue, we conducted paired-sample abundance estimation of L. archeyi in two areas of the Coromandel Peninsula, Te Ika-a-Māui. Sixteen pairs of 100-m2 sites (i.e. sites < 100 m from one another) were surveyed, each comprising of an area which had been disturbed (at least 50% of vegetation removed) by mining exploration or urbanisation during the past 40 years and an area that remained undisturbed over the same period of time. Disturbed sites were subdivided into three categories (1980s, 1990s, and 2020–2016) based on the time elapsed since disturbance. At each site, we performed capture-recapture of frogs over three nights, using their natural markings to identify individuals. We then used a purpose-built closed mark-recapture model to estimate frog abundance. Frog abundances varied among sites but were unrelated to the history of habitat disturbance. Rather, abundance was correlated with higher elevation and with plant species typically associated with mature forest, which was present in both disturbed and undisturbed sites. Ordination techniques used to assess vegetation composition revealed variation among sites that possibly reflects forest succession and replanting in disturbed areas. From our observations, if habitat disturbance does occur we recommend allowing sites to naturally regenerate or to plant species that contribute to leaf litter depth, microhabitat complexity, and increased moisture to promote recolonisation of sites by L. archeyi.