Abstract
Passive acoustic monitoring (PAM) is increasingly being used for the survey of vocalising wildlife species that are otherwise cryptic and difficult to survey. Our study aimed to develop PAM guidelines for detecting the Yellow-bellied Glider, a highly vocal arboreal marsupial that occurs in native Eucalyptus forests in eastern and south-eastern Australia. To achieve this, we considered the influence of background noise, weather conditions, lunar illumination, time since sunset and season on the probability of detecting vocalisations. We deployed Autonomous Recording Units (ARUs) at 43 sites in the Central Highlands of Victoria during two periods: spring/summer (October 2018 to January 2019), and autumn/winter (May to August 2019). ARUs were programmed to record for 11 hours from sunset for 14 consecutive days during each period. Background noise resulted from inclement weather (wind and rain) and masked vocalisations in spectrograms of the recordings, thus having the greatest influence on detection probability. Vocalisations were most common in the four hours after sunset. Rainfall negatively influenced detection probability, especially during the autumn/winter sampling period. Detection of Yellow-bellied Gliders with PAM requires deploying ARUs programmed to record for four hours after sunset, for a minimum of six nights with minimal inclement weather (light or no wind or rain). The survey period should be extended to 12 nights when rain or wind are forecast. Because PAM is less labour intensive than active surveys (i.e., spotlighting and call playbacks with multiple observers and several nights’ survey per site), its use will facilitate broad-scale surveys for Yellow-bellied Gliders.
Highlights
The imperfect detection of wildlife remains a challenge for surveying most species, those species that are cryptic, have large home ranges, and occur at low densities or in inaccessible areas [1]
Count-based metrics suggest that the trend in vocalisations was similar between seasons (S1 Fig); this may have been biased by sites with numerous vocalisations
We demonstrate that Passive Acoustic Monitoring (PAM) is an effective survey method for detecting the presence of Yellow-bellied Gliders, a highly vocal species that commonly occurs at low population densities [29,30,31]
Summary
The imperfect detection of wildlife remains a challenge for surveying most species, those species that are cryptic, have large home ranges, and occur at low densities or in inaccessible areas [1]. Passive acoustic monitoring (PAM) is a remote sensing method that is being applied more frequently for the survey of species that conspicuously advertise their presence, identity, and behavioural traits through vocalisations [9, 10]. With this method, autonomous recording units (ARUs) programmed to record when the species of interest is likely to be vocalising, are deployed at a site for an extended survey period [11, 12]. PAM is effective for use in difficult terrain and vegetation, can be applied across large spatial and temporal scales, is non-invasive, and may improve detection probability of species that are small, nocturnal, elusive or uncommon [1, 12,13,14]
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