Optimal foraging theory
Optimal foraging ( literal meaning: " optimal foraging " ) is a principle of ecology that attempts to explain how decision-making come in search of food and food -select. It is applied to both animals in behavioral biology as to people in archeology and ethnology. In biology, the German term optimality model will be used.
One of the most important core sets assumes that individuals and social groups prefer such food sources that offer the highest possible net energy intake (difference between energy output and energy expenditure ). However, this assumes that these groups evaluate their food sources and exploit accordingly. There are two variables, the time and the food efficiency. That is, it is preferable that food in which the ratio of two variables to one another is preferred. Thus, the concept is used to attempt to explain the relationships between populations, their food sources and spatial distribution, as well as their food strategies.
Basic principle
So-called optimality models describe a behavior- biological system of cost -benefit analysis: Only if the benefits of an action outweigh its costs, it is advantageous and is being implemented. The difference between benefits and costs should be as high as possible.
- Benefits: for example, Energy content of the ingested food
- Cost: expended energy and time, and to the danger of predators
- Benefit - cost = net energy gain
The individual directs his behavior accordingly, as it can maximize the net energy gain.
To put the costs and benefits in an optimum ratio, two strategies can be applied:
- Maximize the uptake rate: It is set to quantity by, for example, while lower-energy food is taken, but in a higher frequency and with less effort.
- Maximize efficiency: It is set to high quality, while using a higher cost for the food profit is spent, but sufficient of the higher energy content of the food for a longer time.
One can extend these models for many other patterns of behavior. Thus, the cost -benefit analysis is also crucial for the group size: For a large group of expense for the defense from predators for the individual smaller and the rate of success in hunting through cooperation higher, but also increases the number of competitors, allowing more time to fight for resources to be expended. Ideally, can be determined as an optimum average, the balance is restored, the group size, and may be most beneficial.
Examples
- Oystercatchers prefer for their food medium sized clams, there is in the small to little nutritional value and the big ones are too expensive to crack.
- Birds that live in hedges, have a limited food supply, but are safe from enemies. The empty space on the food supply is greater, to fall a danger predators prey, as well. With increasing duration of the period of starvation decide more and more birds to feed in the open field.
- In the presence of a predator flocks of pigeons form dense groups to better protect themselves from the enemy can. Since it thereby but is more competition, the groups then dissolve again.
Application to Archaeology and Ethnology
Optimal foraging emerged from the first attempts of the New Archaeology in the 1970s to explain the use of resources and settlement patterns of prehistoric societies by the availability or scarcity of food. The principle was formulated in 1981 in a series of publications by Winterhalder and Smith. As a result, it was applied to hunter- gatherer cultures, especially for the explanation of changes in resource use due to changes in environmental factors. Examples include the introduction of grinding stones in the cultural area of the Great Basin in western North America. By increasing drought in the mid- Holocene had the inhabitants of large tree seeds like acorns on food plants with smaller seeds, especially grasses, dodge. Members of the Numic branch of the Uto- Aztecan family proved to be skillful in using this new technology and prevailed. Their descendants inhabit the region today.
Here, a differentiated analysis of costs and benefits must be applied. When Cree Indians traditionally hunt in the spring with considerable effort beaver, although would easily provide much larger amounts of meat in this season to hunt caribou, this explains the fact that beavers at this time have a much higher fat content.