"Letting nature take its ecosystemic course is why the Yellowstone ethic forbade rescuing the drowning bison, but rescued the sow grizzly with her cubs, the latter to insure that the big predators remain. After the bison drowned, coyotes and magpies, foxes and ravens fed on the carcass. Later, even a grizzly bear fed on it. All this is a good thing because the system cycles on, and the great bear, like the wolves, is a sparkling gem in the network. On that account rescuing the whales trapped in the winter ice seems less of a good thing, when we note that rescuers had to drive away polar bears that attempted to eat the dying whales."