Habitat suitability correlates with mean population fitness of a threatened marsupial predator

Abstract

Context Measuring the quality of habitats necessary for the survival of threatened species is a priority for conservation management, but traditional metrics are often too costly to implement. As a result, many practitioners rely on proxies such as habitat suitability, which are measured by relating environmental variables to species occurrence data using habitat suitability models. However, little research has examined how these proxies relate to actual measures of habitat quality, such as body condition. Aim By testing the relationship between habitat suitability and habitat quality – as characterised by mean population fitness – the aim of this study was to improve our understanding of ways in which we can reliably map habitat of high importance for a particular species, as well as habitats where populations are most susceptible to local extinction. Methods We used data from a large-scale monitoring program on the northern quoll (Dasyurus hallucatus), a threatened marsupial predator, which collected data on three measures of population mean fitness (measured as body mass accounting for size, tail circumference, and body mass). We correlated these measures with habitat suitability derived from a habitat suitability model. Key results We found quoll mean population fitness increased with increasing habitat suitability. In addition, we found mean population fitness increased with increasing topographic ruggedness, annual rainfall, rainfall variability, and decreasing distance to water, consistent with previous studies that suggest quolls are able to persist better in habitat where resource availability (shelter, food) is higher. Conclusions Our findings demonstrate the usefulness of habitat suitability models for predicting habitat quality for a threatened predator at a large scale, and that predictions of habitat suitability can correspond with measures of fitness. In addition, they support previous studies in highlighting the importance of topographically complex habitat for this species. Implications These findings have important implications for identifying both source populations, where species recruitment is likely to exceed mortality, and more vulnerable populations that may require targeted conservation interventions to ensure their long-term persistence and stability.