Viewed from a distance, the natural world often presents a vista of sublime, majestic placidity. Yet beneath the foliage and hidden from the distant eye, a vast, unceasing slaughter rages. Wherever there is animal life, predators are stalking, chasing, capturing, killing, and devouring their prey. Agonized suffering and violent death are ubiquitous and continuous.

Suppose that we could arrange the gradual extinction of carnivorous species, replacing them with new herbivorous ones. Or suppose that we could intervene genetically, so that currently carnivorous species would gradually evolve into herbivorous ones, thereby fulfilling Isaiah's prophecy. If we could bring about the end of predation by one or the other of these means at little cost to ourselves, ought we to do it?

If suffering is bad for animals when we cause it, it is also bad for them when other animals cause it. That suffering is bad for those who experience it is not a human prejudice; nor is an effort to prevent wild animals from suffering a moralistic attempt to police the behavior of other animals. Even if we are not morally required to prevent suffering among animals in the wild for which we are not responsible, we do have a moral reason to prevent it, just as we have a general moral reason to prevent suffering among human beings that is independent both of the cause of the suffering and of our relation to the victims. The main constraint on the permissibility of acting on our reason to prevent suffering is that our action should not cause bad effects that would be worse than those we could prevent.

The claim that suffering is bad for those who experience it and thus ought in general to be prevented when possible cannot be seriously doubted.

It seems, moreover, that my argument has some relevance to choices we must make even now. There are some species of large predatory animals, such as the Siberian tiger, that are currently on the verge of extinction. If we do nothing to preserve it, the Siberian tiger as a species may soon become extinct. The number of extant Siberian tigers has been low for a considerable period. Any ecological disruption occasioned by their dwindling numbers has largely already occurred or is already occurring. If their number in the wild declines from several hundred to zero, the impact of their disappearance on the ecology of the region will be almost negligible. Suppose, however, that we could repopulate their former wide-ranging habitat with as many Siberian tigers as there were during the period in which they flourished in their greatest numbers, and that that population could be sustained indefinitely. That would mean that herbivorous animals in the extensive repopulated area would again, and for the indefinite future, live in fear and that an incalculable number would die in terror and agony while being devoured by a tiger. In a case such as this, we may actually face the kind of dilemma I called attention to in my article, in which there is a conflict between the value of preserving existing species and the value of preventing suffering and early death for an enormously large number of animals.

The suffering that animals undergo while being caught and eaten may be intense and the process by which they are killed may last for a quarter of an hour or more. Because the number of predators worldwide is enormous, and because, like us, many of them must eat with considerable frequency, the aggregate amount of suffering in the world at any time that is caused by predation is unimaginably vast.