PhD project topic: The ecology and conservation of the threatened large-eared pied bat (Chalinolobus dwyeri) and eastern cave bat (Vespadelus troughtoni)

This project combines an ecological and genetic approach to improve our understanding of the ecology and habitat requirements of two of Australia’s threatened insectivorous bat species, the Large-eared Pied Bat (Chalinolobus dwyeri) and Eastern Cave Bat (Vespadelus troughtoni). A core component of the project is the creation of a heat map of calling activity to visualise how the species use landscapes, particularly centred on maternity roosts surrounded by human-modified landscapes. The heat maps are generated from a ‘grid’ of 28 ultrasonic recorders where the number of calls on each recorder is used as an indicator of activity. Titley Scientific’s Anabat Swifts were used to collect high-quality reference calls from both the Large-eared Pied Bat and Eastern Cave Bat, which we will now analyse and extract call metrics from within Titley Scientific’s software Anabat Insight. The call metrics for each species will be used to create fine-tuned decision-tree filters to drastically streamline the process of determining the number of target species’ calls on each recorder in our 28 recorder grids. We will begin the analysis of the audio data in May 2024 and we expect to have the results by September 2024.

Deciding on what call metrics to use to distinguish the Large-eared Pied Bat from other species is relatively straightforward, however, it seems to be almost impossible for the Eastern Cave Bat east of the Great Dividing Range due to the almost complete overlap in call metrics with the Little Forest Bat (Vespadelus vulturnus). Thus, using Titley Scientific’s Anabat Swifts, we also collected reference calls from the seemingly indistinguishable Little Forest Bat to scrutinise their calls for any minute differences. Preliminary observations suggest that human-made call metrics probably won’t be useful in distinguishing the two species, but, upon manual inspection, Eastern Cave Bat does seem to have a sigmoid-shaped call unlike the Little Forest Bat call, particularly when a properly formed pulse is recorded at close distance so that the maximum frequency is higher than about 100kHz (credit to Alfred Schulz). However, further investigation will occur over the next few months to confirm whether this is a reliable feature, so stay tuned!