The Component of Feeding Behavior

Social Stimuli.
The direction of a wild rat’s movements as it goes to eat may also be influence by other rats. In this book the word social is used for any such effect

Barnett & Spencer watched colonies of wild rats when they began to feed in the evening. The food was wheat grains. Usually, one particular member of the colony emerged first, and carried a mouthful of grains back to its nest; the nest was shared with other rats, and these came out soon after the return of the pioneer rat. The possible importance of such individual’s appearance in two kinds of situation. In one, the rats were deprived of food for one or two days, and then food was replaced in the usual containers. The first rat to find the food was the pioneer, and the return of this rat to the nest with food led to a rapid and unanimous sortie by the rest of the colony. This occurred, as one would expect, especially when the rats had had previous experience of a fast followed by a return of food .

In second kinds experiment , food for instance, cabbage, put in the enclosure was of kind only rarely available to the rats. The first rat to emerge at once took a cabbage leaf and returned with it to the nest. This was followed by general activity, including excursions for additional leaves and attempts to wrest fragments of leaf from other rats.

The habit of taking food to the nest, end of eating it under cover, , had other indirect social effects. Grains dropped from a rat’s mouth, as a preliminary to eating them one by one , were often taken by other rats. If a rat had been eating flour, residues on its face or hands were licked off by other rats, especially young one

The rats had probably come to associate certain behavior of other rats, or certain appearances or odors , with the presence of food. The fact that a social interaction is involved is incidental.

FEEDING BEHAVIOR

Not one man in a billion, when taking his dinner, ever thinks of utility. He eats because the food tastes good and makes him want more. If you ask him why he should want to eat more of what tastes like that, instead of revering you as a philosopher he will probably laugh at you at for a fool
William James

General
Much of the behavior described in the preceding chapter is only indirectly related to the primary needs-those that must be satisfied if the animal is to survive for more than a few minutes, hour or days. The internal processes which determine that animals behave so as to satisfy these needs are sometimes called the homeostatic drives. They are set in motion by a departures from some internal state, such as the concentration of sodium ion in the body fluids, the amount of carbon dioxide in the blood or the temperature of the skin: for each of these there is a narrow range of values which a mammal tends to maintain.

This chapter deals with the activities which maintain a rat’s intake of food and water. The feeding of most animals is regulated by complex mechanism; but in studying an omnivorous mammal we are taking on the most difficult of the possible tasks. Omnivory, however, is not special to the genus, Rattus, or even to the family Muridae. Although the rodents are specialized. In their dentition and in head structure, for eating plant food, such as grains, many of those that have been studied closely have proved to be versatile feeders.

The voles of the genus, microtus , feed principally on the softer parts of rough grasses; but they readily take to roots, such as carrots or turnips; and they also eat grain. Apodemus and Clethrionomys , too, are adaptable feeders. Squirrel (Sciuridae) eat hard fruit and seeds, but also young shoots and buds, young bark , roots and even insect. Gerbils, such as Meriones, may eat land snails. In some conditions half the diet may be insect, especially termites.

Rats can also be predators on smaller mammals, birds and even fish. The factors which regulate feeding in natural conditions are almost unknown. Since we are principally concerned with the results of experimental analysis, we are obliged in this chapter to rely almost entirely on observations of laboratory rats.