Abstract
Defining species habitat requirements is essential for effective conservation management through revealing agents of population decline and identifying critical habitat for conservation actions, such as translocations. Here we studied the habitat-associations of two threatened terrestrial-breeding frog species from southwestern Australia, Geocrinia alba and Geocrinia vitellina, to investigate if fine-scale habitat variables explain why populations occur in discrete patches, why G. alba is declining, and why translocation attempts have had mixed outcomes. We compared habitat variables at sites where the species are present, to variables at immediately adjacent sites where frogs are absent, and at sites where G. alba is locally extinct. Dry season soil moisture was the most important predictor of frog abundance for both species, and explained why G. alba had become extinct from some areas. Sites where G. alba were present were also positively associated with moss cover, and negatively with bare ground and soil conductivity. Modelling frog abundance based exclusively on dry season soil moisture predicted recent translocation successes with high accuracy. Hence, considering dry season soil moisture when selecting future translocation sites should increase the probability of population establishment. We propose that a regional drying trend is the most likely cause for G. alba declines and that both species are at risk of further habitat and range contraction due to further projected regional declines in rainfall and groundwater levels. More broadly, our study highlights that conservation areas in drying climates may not provide adequate protection and may require interventions to preserve critical habitat.
Highlights
Defining the environmental factors that determine species distributions is invaluable for effective species conservation and management
We studied the habitat-associations of two threatened terrestrial-breeding frog species from southwestern Australia, Geocrinia alba and Geocrinia vitellina, to investigate if fine-scale habitat variables explain why populations occur in discrete patches, why G. alba is declining, and why translocation attempts have had mixed outcomes
Geocrinia alba and G. vitellina habitats were sampled across four distinct site types, selected with reference to long-term acoustic monitoring records maintained by the Western Australian Department of Biodiversity, Conservation and Attractions (DBCA) (Fig. 1)
Summary
Defining the environmental factors that determine species distributions is invaluable for effective species conservation and management. Species-habitat associations can be used to identify threatening processes and enable management actions that may halt or reverse declines, and prevent species extinctions (Caughley 1994). Defining species’ habitat requirements can improve recovery actions, such as conservation translocations (Morris et al 2015; McCulloch and Norris 2001). A key challenge for recovering threatened species is identification of suitable reintroduction sites, and low habitat suitability or a lack of consideration of micro-habitat are prime reasons for translocation failure (Germano and Bishop 2009; Bennett et al 2013). Despite potential benefits to conservation, the fine-scale habitat associations that determine a species occurrence are often unknown
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