ABSTRACT
Passive acoustic monitoring is a major new tool for applied ecology and conservation, allowing cost-effective biodiversity monitoring for vocal species. However, like all survey methods, care needs to be taken in how such data are collected, analysed and interpreted. We respond to a recent paper by Smith and Pile (2024) that made simplistic use of koala calling to make assertions about sex-based habitat use, and we point out serious flaws in how the data were used. We respond by outlining recommended practices for collecting, analysing and interpreting acoustic data, especially those targeting koalas. Smith and Pile (2024) used raw single-visit male calling rate to suggest that this creates problems for defining koala habitat use of males compared to females. Conversely, we argue that raw calling data should not be used to make these assessments because imperfect detection (false negatives) needs to be accounted for prior to estimating occupancy or density. Because male koalas are the primary sex that bellows, the method is sex-biased, although sex ratios for koalas are commonly 1:1. Further, assessment of sex-based habitat use is best undertaken at fine scales by radio-tracking and GPS-tracking, especially at night when koalas are actively browsing. Such studies reveal minor differences but substantial overlap in habitat use between the sexes. When analysing acoustic surveys, the environment needs to be assessed in the local landscapes surrounding sensors (e.g. 500 m buffer) rather than the actual sensor location. Passive acoustics can provide cost-effective assessments of occupancy at regional scales when applied across many sites. Alternatively, when used in arrays, acoustic surveys can provide density estimates at local scales. These multiple lines of complementary, supporting evidence are presented to support previous findings for koalas based on passive acoustics, contrary to the aproach proposed by Smith and Pile (2024).
