Just before dawn, a red junglefowl (Gallus gallus) cock crows from his roost in the bushes. Then, as it begins to get light, he makes his way to the ground with his group of three females and starts his daily search for food, scratching in the leaf litter for seeds and, if he is lucky, worms and grubs. In the heat of the day, he will return to the bushes for a siesta, but later he will resume his feeding on the ground, perhaps breaking off to dustbathe, mate with the females or search for water. All the time, he keeps a wary eye out for predators and rival males, ready to disappear into the undergrowth or see off an intruder at a moments' notice. As it gets dark, the group leave the ground in preparation for spending the next night in the relative safety of the bushes.
This simple description of the day in the life of one animal illustrates perfectly just how complex animal behaviour is. At every moment of every day an animal can be said to be making ‘decisions’ about what to do next – choosing to do one thing rather than another, or choosing to stop what it is doing and start something else. And those decisions can be studied at every level ??? from the level of the whole day, in which the decisions are between which parts of the day to be active and which parts to hide or sleep, right down to the moment-to-moment decisions about whether at this second to peck down at a food item or look up to see if there is a predator around. Indeed, we can look at even longer time scales, such as how behaviour changes over a whole year or even a whole lifetime.