Foraging Behavior in Animals
Understanding Animal Food-Searching Strategies
Foraging theory explores the foraging behavior of animals in relation to the metabolic payoff an animal receives when employing a number of different foraging options.
Most animals are adapted structurally and physiologically to feed on a limited range of food and to gather this food in specific ways. For many animals, food comes in a variety of sizes. Larger foods may contain more energy but be harder to capture or obtain.
Also, some food may be further away than other types. Hence, foraging (finding food) involves a trade-off between a food’s energy content and the energy expended to obtain the food – the net energy intake. Foraging theory predicts that the foraging strategies that deliver the greatest net energy intake should be those most favored by foraging animals because they will deliver the highest fitness payoff.
The Optimal Foraging Theory
One of the first foraging theories to be developed was the optimal foraging theory in 1966.
According to this theory, natural selection favors individuals whose foraging behavior is as energy efficient as possible. That is, the most successful animals tend to feed on items that maximizes their net energy intake per amount of foraging time. That in turn should lead to increases in reproductive success. And that does seem to be the case. Studies on ground squirrels, captive zebra finches, and orb-weaving spiders have shown a direct relationship between net energy intake and the number of offspring raised.
Optimal foraging theory argues that because optimal foraging is critical to survival, it should be possible to predict the behavior of an “optimal forager.” (An optimal forager is defined as an individual with perfect knowledge of exactly how to best maximize food intake.)
There are several versions of the optimal foraging theory depending on the specific foraging situation:
- Central place foraging which describes the foraging behavior of an animal that returns to a specific place to feed or offer food to a mate or offspring
- Patch selection foraging which describes the foraging behavior of an animal whose prey is concentrated in small patches with considerable travel time between patches.
- Optimal diet foraging which describes the foraging behavior of an animal that encounters a variety of prey and must decide which prey to attack.
While actual foraging behavior of real animals inevitably varies from the model, optimal foraging theory has proven quite useful in developing hypotheses for understanding real foraging behavior. Actual foraging behavior compared to predicted foraging behavior helps to identify constraints either in the animal's behavioral or cognitive repertoire, or in the environment, that had not previously been suspected. With those constraints identified, foraging behavior often does approach the optimal pattern even if it is not identical to it.
Foraging Strategies can be Compromised
However, highly successful foraging strategies can be complicated and compromised by matters of ecology, age, mate selection, and prey avoidance. An example of how differences in ecology can alter foraging strategies would be that in the relatively unproductive marshes of northeastern United States, great blue herons must spend a great deal more time finding food than herons in Florida where marsh productivity is much higher and food is easier to find.
Age plays a role in the foraging of the small North American bird known as the yellow-eyed juncos. Even though large prey contains more energy, young juncos lack the experience to handle large prey. They focus instead on smaller prey until they are older and experienced enough to easily dispatch larger prey.
Many studies have shown that a wide variety of animal species alter their foraging behavior – become less active and staying near cover – when predators are present. However, finding a mate is such a driving force that males of many animal species throw caution into the wind not only reducing their foraging time but also exposing themselves to predators in order to find a mate.
Studying and understanding foraging behavior provides behavioral ecologists with yet another piece to the puzzle that is the total behavior of an animal within its natural environment.
Foragers Come in All Sizes
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