Emergence and return times in a colonial, cave-dwelling bat: age and sex differences driven by reproductive cycle

The time that bats emerge, and subsequently return, from a colonial roost determines their maximum foraging period and influences their exposure to mortality risks. The order in which different age and sex cohorts emerge and return reflects variation in these cohorts’ resource requirements. The critically endangered Southern Bent-wing Bat (Miniopterus orianae bassanii) is an Australian insectivorous cave-roosting colonial bat. Resource limitation is hypothesised to have contributed to its decline, but may not affect all cohorts equally. We tagged and monitored 3,462 wild Southern Bent-wing Bats over seven years with Passive Integrated Transponder technology. To infer resource requirements of different cohorts over the reproductive cycle, we estimated cohort-specific peak emergence and return times and the frequency of nocturnal returns to the roost. The emergence and return behaviour varied with age, sex, and throughout the annual reproductive cycle. Although adult females and males beh..., Study sites
Southern Bent-wing Bats were monitored at a maternity roost and an associated non-maternity roost from 2016 to 2022. The maternity roost is located in Bat Cave, a multi-chambered cave within the Naracoorte Caves National Park World Heritage Area in south-east South Australia. Southern Bent-wing Bats congregate here in the austral spring to form a maternity colony. Occupancy peaks in summer, when the site is occupied by approximately 28,000 adult bats, comprising both females and males of all ages (Hamilton-Smith, 1972). The cave entrance is a collapsed window measuring approximately 8 × 4 m, surrounded by vegetation of varying heights. 
The non-maternity roost is approximately 70 km from the maternity roost. Here, the cave entrance is in a large doline (a funnel-like depression in the ground), and measures approximately 6 × 2 m. The cave is situated on a dairy farm and is surrounded by cleared pastures. Southern Bent-wing Bats are known to move regularly between this si..., # Emergence and return times in a colonial, cave-dwelling bat: age and sex differences driven by reproductive cycle

Dataset DOI: [10.5061/dryad.31zcrjdzn](10.5061/dryad.31zcrjdzn)

## Description of the data and file structure

Detection data were collected from 3,462 wild Southern Bent-wing Bats via in-cave PIT-tag readers from 2016-2022. Detection data were linked to capture data to identify the sex and age of bats. The year was split into 4 reproductive periods: pregnancy, lactation, weaning, and non-breeding.

To calculate emergence and return times, detection data were filtered to exclude observations an hour after sunrise through to an hour before sunset. Data were binned into 5-minute intervals for each night of the study, and cohort detections were tallied. The moving average over 3 5-minute intervals with the highest number of detections was selected as emergence time (before midnight), measured in time since sunset, or return time (after midnight), measured in time to sunrise...,