Australian flying-foxes are prone to mass heat-stress die-offs, with some recent die-offs at extreme scales of over 45,000 individuals in a single event. We developed a model to predict which flying-fox roosts were most at risk of such events. Our model not only uses environmental factors, but also physiological factors such as fur properties and behaviours like panting, licking and fanning. This research will be used to extend a “Flying-fox Heat Stress Forecaster” which helps the management of flying-fox camps during extreme heat events.