Foraging Basics

In general foraging is an evolutionary game, or arms race, between the consumer and the microbes, fungi, plants or animals which it wishes to consume. The evolutionary pressure to consume food is strong, as animals which fail to find food are unlikely to reproduce. Organisms which are consumed, of course, also lose their reproductive potential. Adaptations to enhance consumption, countered by adaptations which deter consumers, are the rules of the game.

These principles apply equally to animals whose diet is predominantly plant material (herbivores, frugivores, and nectarivores), those which mostly eat animals (carnivores), and those which slowly consume their prey from the inside (parasites). Scavengers on carrion, consumers of decaying plant material (detrivores or saprophages), and dung-eaters (coprophages) do not run into defenses produced by their food, but are subject to intense competition from microbes and fungi for these types of food; this leads to the same sort of arms race, this time in competition for the food item.

One interesting variation on this arms race is the strategy of predator saturation.

Even though diets can be classified by their dominant food type, many animals supplement their diet and enhance their nutrition by adding other foods. Deer, for example, might be thought of as strict herbivores, browsing on leaves, flowers and fruits. Yet observations show that given the opportunity they consume nestling birds in grasslands. Carnivores often add to their diet by consuming small amounts of plant material.

Omnivores have more truly mixed diets. They have the advantage of being able to take in a broader range of food items, but may lack the specializations necessary to take advantage of many of the plants and animals in their environment. Humans have succeeded as omnivores largely because we can hunt cooperatively, use tools to enhance our hunting armament, which is poor at best without tools, and expand our food supply by domesticating plants and animals. Technology takes the place of evolved specialization in forming our diet.

The evolutionary arms race between consumers and the consumed leads to specialization. Many animals can only eat a small range of food items. They have specific adaptations to overcome the defenses of certain food species, and their diet is restricted to those. This is true of both herbivores and carnivores, and understanding dietary specialization is key to developing a broader knowledge of foraging behavior.