Even a human can cause such losses in extreme heat. As a kid I used catch some of my game stags by literally running them down which required a sustained run by me approaching 15 minutes. Humans are really good at such relative to other animals, especially when it is hot outside. I also ran down some Rhode Island Reds that did not roost in building where they could be found. The Rhode Island Reds were much less capable of dumping heat and quickly got to the point where they seemed forget where they were going and would suddenly start running in a straight line even when I was about to grab them. More than one then simply laid down in the open but would keep going if I pused the issue. I learned quickly that recovery from such was much quicker if chase ended with capture well before the point they seemed to forget I was there. Same birds during winter where much more capable and did not seem to get delirious. The delirium was likely a step shy of death. Also when stags got into major fights on hot days, death when occurred was too rapid to come from actual battle damage.