cyanograss
apparently some genetically modified grass went a mutant and started producing cyanide gas. which killed the cows that were eating it. all hail our new grassy overloads. heh. i'm wondering if this sort of thing hasn't happened many times before. there've been reports of carbon dioxide poisoning killing predators scavengers and prey alike. the only survivors would be the ones that walk upright. and can reach down with their long arms to collect the bounty of all this fresh meat. and live. when the competition dies.