It depends largely on how specialised they have become during the course of evolution. If they have put all their evolutionary effort into the perfection of one particular survival trick, they do not need to bother so much about the general complexities of the world around them. So long as the ant-eater has its ants and koala bear its gum leaves, then they are well satisfied and the living is easy. The nonspecialists, on the other hand—the opportunists of the animal world—can never afford to relax. They are never sure where their next meal may be coming from, and they have to know every nook and cranny, test every possibility, and keep a sharp look-out for the lucky chance. They must explore, and keep on exploring. They must investigate, and keep on re-checking. They must have a constantly high level of curiosity. It is not simply a matter of feeding: self-defence can make the same demands. Porcupines, hedgehogs and skunks can snuffle and stomp about as noisily as they like, heedless of their enemies, but the unarmed mammal must be forever on the alert.
