I would discard ambient temperature, both species support a lot of heat. neither lack of food fits because all cohorts died simultaneously. Toxins, poison or h

I would discard ambient temperature, both species support a lot of heat. neither lack of food fits because all cohorts died simultaneously. Toxins, poison or hidden radioactivity dust most probably [1] if I remember correctly Saiga mortality in Kazahstan happened a few months after wildfires in Chernobyl. Is also an area contaminated with fuel rockets. There are two species of Saiga currently so this makes the problem much worse. Is a fact that elephants have an enemy in farmers, and that lions and other African wild fauna had been systematically poisoned in recent years to be replaced by cattle. [1] triggering low immunity, that leads to opportunist bacterial infections, that leads to (or just facilitate), mass death at all levels.