Abstract
Surveying terrestrial species across diverse habitats is important for predicting species’ distributions and implementing conservation actions. For vocalising species, passive acoustic monitoring (PAM) is increasing in popularity; however, survey design rarely considers the factors influencing the timing and occurrence of vocalisations and in turn, how they may influence detectability of the species. Here, we use the koala (Phascolarctos cinereus) as a case study to show how PAM can be used to first examine the factors influencing vocalisations, and then use occupancy modelling to make recommendations on survey design for the species. We used automated recording units to monitor koala vocalisations at ten sites between August 2016 and January 2017. The timing of male koala vocalisations was linked to time of sunset with vocalisations increasing two hours prior to sunset and peaking at four hours after sunset. Vocalisations had a seasonal trend, increasing from the early to middle stage of the breeding season. Koala population density and stage of the breeding season had more influence on detection probability than daily sampling schedule. Where population density was low, and during the early stage of the breeding season, 7 survey nights (recording for 6 hours from 20:00h to 02:00h; i.e. the period of peak bellowing activity) were required to be 95% confident of a site-specific absence. Our study provides an approach for designing effective passive acoustic surveys for terrestrial species.
Highlights
The ability to detect and monitor terrestrial wildlife species is critical for predicting distributions and for managing populations [1, 2, 3]
We demonstrate how the use of Passive Acoustic Monitoring (PAM) for detecting a terrestrial species can be optimised by first obtaining information on how vocalisations vary with population density and seasonal activity of a species, and using occupancy modelling to determine the optimal sampling schedule relative to these factors
Male bellow occurrence varied between sites and was positively correlated with the double-count estimate of koala population density (Pearson’s r = 0.831, P = 0.003; Table 2)
Summary
The ability to detect and monitor terrestrial wildlife species is critical for predicting distributions and for managing populations [1, 2, 3]. Most traditional field survey methods are labour intensive and imperfect detection of species remains a challenge, especially for those species that are cryptic, or that occur at few sites or at low densities [4]. The development of reliable, efficient and cost-effective monitoring techniques is important [5, 6]. Passive Acoustic Monitoring (PAM) is an emerging technique for monitoring terrestrial species across a diversity of taxa [7]. Autonomous Recording Units (ARUs) that are programmable, small, deployed and which can be left in the field for extended periods allow.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
