It is almost impossible to evaluate all costs and benefits that came our way from the Carnivora. The animals give us great pleasure, warmth and companionship, we have eaten and used them, they have eaten and used us, and we have had to take costly measures for protection. But the chances are that on balance, over the period of existence of our species, we have lost to them, and that in economic terms they have cost us more than they have paid us back. We will see later in Chapter 11 that similarly, the carnivores themselves, in all probability, have lost more than they have gained from us.

It is useful, then, to see how other animals fare in the presence of predators. After all, just about every species suffers from predation. How, in general, do carnivores affect the numbers of their prey species? Often, one glibly talks about a ‘balance of nature’, suggesting that negative forces that act on populations are corrected by others. But what exactly happens, how does it work? Is there, indeed, a balance of forces or are appearances deceptive? These are important ecological questions in themselves, and they have to be answered, before in the following chapter, we can evaluate the anti-predator systems of animals in general, and the anti-predator behaviour of mankind.