Optimal foraging

Optimal foraging (literal meaning: “optimal foraging ”) is a principle of ecology that tries to explain how decisions are made when searching for and choosing food. It is applied to both animals in behavioral biology and humans in archeology and ethnology . The German term optimality model is also used in biology .

One of the most important core tenets assumes that individuals and social groups prefer those food sources that offer the highest possible net energy intake (difference between energy yield and energy expenditure). However, this presupposes that these groups evaluate their food sources and use them accordingly. There are two variables involved, time spent and nutritional efficiency. That is, the food is preferred in which the relationship between the two variables is most favorable. The concept is used to try 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 behavioral biological system of cost-benefit analysis : only if the benefit of an action outweighs its costs , is it advantageous and implemented. The difference between benefits and costs should be as high as possible.

Benefit : e.g. B. Energy content of ingested food
Costs : energy and time expended, as well as the risk of predators
Benefits - costs = net energy gain

The individual orients his behavior according to how he can maximize the net energy gain.

To put costs and benefits in an optimal relationship, two strategies can be used:

Maximizing the intake rate:
The focus is on quantity , for example by consuming less energy-consuming food, but with a higher frequency and less effort .

Maximizing efficiency:
The focus is on quality , in that a greater amount of effort is put into gaining food, but the higher energy content of the food is sufficient for a longer period of time.

These models can also be extended to many other behavioral patterns. The cost-benefit analysis is also decisive for the group size: In a large group, the effort to defend against enemies is lower for the individual and the success rate in hunting through cooperation is higher, but the number of competitors also increases , which means more Time has to be spent fighting for resources. In the ideal case, an optimal mean value can be determined, on which the group size levels off and can most advantageously exist.

Examples

Oystercatchers prefer medium-sized mussels for their food, as there is not enough nutritional value in the small ones and the large ones are too difficult to crack.
Birds that live in hedges have limited food, but are safe from predators. In the open field the food supply is greater, but so is the danger of falling victim to predators. As the hunger phase increases, more and more birds decide to feed in the open field.
In the presence of a predator, flocks of pigeons form denser groups in order to better protect themselves from the enemy. Since this creates more competition, the groups then break up again.

Application to archeology and ethnology

Optimal foraging emerged from the first attempts of New Archeology in the 1970s to explain the resource use and settlement patterns of prehistoric societies by the availability or scarcity of food. The principle was formulated in a series of publications by Winterhalder and Smith in 1981. Subsequently, it found application to hunter-gatherer cultures, particularly to explain changes in resource use due to changes in environmental factors. Examples are the introduction of millstones in the cultural area of the Great Basin in western North America . Due to increasing drought in the Middle Holocene , the inhabitants had to switch from large tree seeds such as acorns to food plants with smaller seeds, especially grasses. Members of the Numic branch of the Uto-Aztec language family proved to be more adept at using this new technology and prevailed. Their descendants still inhabit the region today.

A differentiated consideration of costs and benefits must be applied. If Cree Indians traditionally hunt beavers with considerable effort in spring , even though the hunt for caribous would more easily produce much larger quantities of meat at this time of the year, this is explained by the fact that beavers have a much higher fat content at this time.

literature

Winterhalder, B. and Smith, EA (Eds.) (1981). Hunter-gatherer foraging strategies . Chicago: University of Chicago Press.

Web links

University of Würzburg on the principle of optimality in behavioral biology:
- Word document (summary)
- PDF document
Behavioral Science.de on the principle of optimality

Individual evidence

↑ This chapter is based on: David R. Yesner: Ecology in Archeology . In: R. Alexander Bentley, Herbert DG Maschner, Christopher Chippindale: Handbook of Archaeological Theories . Altamira Press, 2008, ISBN 978-0-7591-0032-9 , p. 39-56, 46f.
^ R. Alexander Bentley et al .: Darwinian Archaeologies . In: R. Alexander Bentley, Herbert DG Maschner, Christopher Chippindale: Handbook of Archaeological Theories . Altamira Press, 2008, ISBN 978-0-7591-0032-9 , p. 109-132, 119f.

[1] This chapter is based on: David R. Yesner: Ecology in Archeology . In: R. Alexander Bentley, Herbert DG Maschner, Christopher Chippindale: Handbook of Archaeological Theories . Altamira Press, 2008, ISBN 978-0-7591-0032-9 , p. 39-56, 46f.

[2] R. Alexander Bentley et al .: Darwinian Archaeologies . In: R. Alexander Bentley, Herbert DG Maschner, Christopher Chippindale: Handbook of Archaeological Theories . Altamira Press, 2008, ISBN 978-0-7591-0032-9 , p. 109-132, 119f.