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Passive acoustic surveys for predicting species' distributions: Optimising detection probability
Stiele V Hagens1, Anthony R Rendall1, Desley A Whisson1
1School of Life and Environmental Sciences, Centre for Integrative Ecology, Deakin University, Geelong, Australia.
Plos One
|July 19, 2018
Summary
Passive acoustic monitoring (PAM) for koalas (Phascolarctos cinereus) reveals vocalizations peak after sunset and during the breeding season. Optimal survey design requires considering these factors for accurate species detection.
Area of Science:
- Ecology
- Bioacoustics
- Conservation Biology
Background:
- Terrestrial species surveys are crucial for distribution prediction and conservation.
- Passive acoustic monitoring (PAM) is a growing technique for vocal species.
- Effective survey design for PAM must account for vocalization patterns and detectability.
Purpose of the Study:
- To investigate factors influencing koala (Phascolarctos cinereus) vocalizations using PAM.
- To develop recommendations for optimizing koala survey design based on vocalization patterns.
- To demonstrate an approach for designing effective passive acoustic surveys for terrestrial species.
Main Methods:
- Utilized automated recording units for koala vocalization monitoring across ten sites (August 2016 - January 2017).
- Analyzed vocalization timing in relation to sunset and seasonal breeding stages.
- Employed occupancy modeling to assess the influence of population density, breeding stage, and sampling schedules on detection probability.
Main Results:
- Koala male vocalizations were strongly linked to sunset, increasing pre-sunset and peaking post-sunset.
- Vocal activity showed a seasonal trend, rising from early to mid-breeding season.
- Population density and breeding stage significantly impacted detection probability more than daily sampling frequency.
Conclusions:
- Koala vocalizations exhibit predictable temporal patterns influenced by time of day and season.
- Effective koala PAM survey design should prioritize sampling during peak vocalization periods (post-sunset, breeding season).
- A minimum of 7 survey nights (6 hours/night from 20:00h) are recommended for 95% confidence in absence detection in low-density areas during early breeding season.