The impact of extreme heat on Pteropus medius (Indian flying fox)

Climate change has induced extreme heat events that have caused mass die offs of large fruit bats in the genus Pteropus in many parts of the world. The geographic range of Indian flying foxes (Pteropus medius) is continuously shrinking, and their distribution has changed from the hot southern regions to the central and northern regions in Pakistan, likely to avoid rising temperatures and extreme heat events. Recent studies predict far more frequent and intense heat waves in coming years in Pakistan. Therefore, predicting potential places and times of elevated risk of heat-related die-offs for wildlife, especially flying foxes, is of great conservation value, by allowing timely mitigation plans. Environmental factors such as temperature and relative humidity influence thermoregulatory behaviors of P. medius which can accelerate human-bat conflict near water bodies, which are considered as hyper reservoir of antimicrobial resistance (AMR) bacteria and antimicrobial resistance genes (ARGs). Frequent contact of P. medius with water resources for thermoregulation may lead to higher levels of AMR E. coli isolation in their fecal samples. Besides monitoring well characterized sequential thermoregulatory behaviors of P. medius using video scan sampling technique, heat stress can also be quantified at physiological level by measuring the concentration of fecal cortisol metabolites (FCM) using non-invasive sampling technique. I hypothesize that physiological stress experienced by P. medius due to heat stress and population density can lead to higher FCM concentration, in accordance with the cortisol activity hypothesis and the Christian stress hypothesis. I hypothesized P. medius can harbor AMR bacteria because of its proximity to anthropogenically AMR polluted environments and reliance on contaminated water sources. To address these hypotheses, I collected a year around fecal samples from seven roosting sites of P. medius that differ thermally, located in heterogenous landscapes in central and northern Pakistan. I determined temperature and heat stress index thresholds for thermoregulatory behaviors in P. medius at each studied roost. I explored the role of land use and land cover (LULC) variables (forest, crop cover, built-up surfaces and water) in influencing Land Surface Temperature (LST) at seven different sizes (700 m to 22.4 km buffers radius around the roosting sites. I tested the influence of LULC on heat stress index thresholds for thermoregulatory behaviors in P. medius. Comparable to Australian Pteropus, we found a sequence in thermoregulatory behaviors that intensified with increasing temperature and heat stress index. The effect of forest cover and water was strongest at the 700 m buffer radius and gradually weakened with increasing spatial scale. I found a positive relationship between behavioral thresholds and forest cover and water availability around the roost, suggesting greater thermal tolerance in forested landscapes. I did not find any statistically significant influence of extreme heat period and population density on FCMs as predicted by the cortisol activity hypothesis and the Christian stress hypothesis. I found moderate to high level of AMR in E.coli isolates from P. medius against twelve tested antibiotics class. The presence of resistance against reserve antibiotics that are authorized for human use only (aztreonam and imipenem) was found. ESBL-producing E. coli and its associated ARGs (blaCTX-M and blaTEM) were isolated as indicators of the resistome shaped by human activities. This research highlights how rising temperatures and land use changes not only threaten P. medius survival but also increase environmental AMR exposure. Our findings indicate the intricate relationship between land cover and bat thermoregulatory behaviors, underscoring the importance of forestation and optimizing water resources, as Nature-based Solutions for mitigating heat stress in P. medius in natural settings.