Synchronous abortion events in the grey-headed flying-fox (Pteropus poliocephalus)

Context. The grey-headed flying-fox (Pteropus poliocephalus) is a vulnerable species endemic to eastern and south-eastern Australia. Environmental stressors are important contributors to physiological stress, leading to synchronous abortions. We investigate the possibilities of weather conditions and anthropogenic disturbances contributing to synchronous abortion events in a grey-headed flying-fox (Pteropus poliocephalus) roost. Methods. We recorded observations of two synchronous abortion events in a flying-fox roost in Tamworth, New South Wales (NSW), Australia, during October 2017 and August 2019. Key results. Roost searches found similar to 200 (October 2017) and 41 (August 2019) foetuses, equating to similar to 0.5% and >0.1% of adults present at the time, respectively. Neither event was associated with significantly colder than average temperatures nor hot extremes (>42 degrees C). Synchronous abortions cannot be easily attributed to unusually cold or hot site conditions. However, the surrounding region suffered from rainfall deficiencies, known to cause failure of flowering in diet plants, in the 6 months preceding both abortion events. Notably, no rainfall deficiency occurred in 6 months preceding August 2015 when colony size was also large, and no synchronous abortions occurred. Conclusions. Natural background rates of abortions are unlikely to explain the abortion events. The 2017 abortion event coincided with intense harassment of flying-foxes using noise agents; thus, it is possible that physiological stress was a contributor. The 2019 abortion event was associated with harassment of lesser intensity but coincided with a severe food shortage throughout surrounding regions.