Case Report of Unusual Mortality of Egyptian Fruit Bat (Rousettus aegyptiacus) in northern Cyprus.

We report an unusual mortality event affecting the isolated Egyptian fruit bat (Rousettus aegyptiacus) population in northern Cyprus, combining clinical admissions, microbiological findings, and roost surveys to assess magnitude and potential drivers. From January to June 2025, the Cyprus Wildlife Research Institute (CWRI) Wildlife Hospital received an unprecedented surge in admissions with 12 individuals (compared with a total of 16 admissions from 2017 to 2024), with high acute mortality: most bats arrived moribund and died within 12-24 h. Clinical records noted localized purulent lesions and abscesses in 58% of cases. Bacteriological culture and PCR assays recovered Staphylococcus aureus from abscesses and skin swab samples in multiple individuals; isolates exhibited susceptibility to tested antibiotics. Necropsy sampling confirmed viable S. aureus in several specimens despite prolonged storage. Concurrent targeted surveys of 10 known roosts in Feb-Mar 2026 documented marked declines at multiple historical sites, including reductions from hundreds to single-digit counts at formerly large colonies and the complete absence of bats at multiple roosts. No clear evidence of recent human disturbance, extreme weather anomalies, or reduced food availability was found; shotgun cartridges from historical hunting were present, but no direct anthropogenic cause was apparent. Although S. aureus infections-seasonally concentrated in winter-are consistent with observed lesions and may have contributed to morbidity and mortality, causality for the population-level declines remains unknown, and other factors (toxins, unassessed pathogens, and multifactor stressors) cannot be excluded. Given the genetic isolation and conservation significance of the Cyprus Egyptian fruit bat population, these findings are concerning. We recommend urgent, coordinated longitudinal population monitoring, expanded pathogen surveillance including whole-genome sequencing of S. aureus isolates, toxicological screening, and development of a species recovery plan incorporating emergency response, habitat protection, and public outreach.