thumb|[[Grizzly bear (Ursus arctos horribilis) mother and cubs foraging in Denali National Park, Alaska.]]

Foraging is searching for wild food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce. Foraging theory is a branch of behavioral ecology that studies the foraging behavior of animals in response to the environment where the animal lives.

Behavioral ecologists use economic models and categories to understand foraging; many of these models are a type of optimal model. Thus foraging theory is discussed in terms of optimizing a payoff from a foraging decision. The payoff for many of these models is the amount of energy an animal receives per unit time, more specifically, the highest ratio of energetic gain to cost while foraging. Since an animal's environment is constantly changing, the ability to adjust foraging behavior is essential for maximization of fitness. Studies in social insects have shown that there is a significant correlation between learning and foraging performance. Observing and learning from other members of the group ensure that the younger members of the group learn what is safe to eat and become proficient foragers.

One measure of learning is 'foraging innovation'—an animal consuming new food, or using a new foraging technique in response to their dynamic living environment. Foraging innovation is considered learning because it involves behavioral plasticity on the animal's part. The animal recognizes the need to come up with a new foraging strategy and introduce something it has never used before to maximize his or her fitness (survival). Forebrain size has been associated with learning behavior. Animals with larger brain sizes are expected to learn better. In this study, bird orders that contained individuals with larger forebrain sizes displayed a higher amount of foraging innovation. Examples of innovations recorded in birds include following tractors and eating frogs or other insects killed by it and using swaying trees to catch their prey. This type of learning has been documented in the foraging behaviors of individuals of the stingless bee species Trigona fulviventris. Honey bee foraging activity occurs both inside and outside the hive for either pollen or nectar. Similar behavior is seen in many social wasps, such as the species Apoica flavissima. Studies using quantitative trait loci (QTL) mapping have associated the following loci with the matched functions; Pln-1 and Pln-4 with onset of foraging age, Pln-1 and 2 with the size of the pollen loads collected by workers, and Pln-2 and pln-3 were shown to influence the sugar concentration of the nectar collected. Rovers used the strategy of moving across multiple patches in search for food, while sitters remained in one patch with no inclination to go searching. Both of these strategies are polymorphic traits that naturally occur within the larval stages of fruit flies. The gene responsible for major effects on foraging behavior in Drosophila melanogaster larvae is the chaser (Csr) gene. During the study, homozygous strains were produced by crossing the rovers with rovers and sitters with sitters. An example of this balanced risk can be observed in the foraging behavior of the amphipod Ampithoe longimana.

Parasitism

Parasitism can affect the way in which animals forage. For an organism to counteract the procurement of a parasite, they may display avoidance towards certain areas where parasites have previously been discovered. This avoidance behavior is a trade-off mechanism where the loss of time and energy in avoiding food patches is traded with the decrease in risk of contracting a parasite. Adaptations in diet also help in the prevention of parasitic infection. By avoiding foods that have high potential for parasitic contamination, as well as including food items that contain anti-parasitic properties in the diet. These anti-parasitic properties can be used in a self-medicating way, either prophylactically or therapeutically. For instance, Blepharida rhois differ in their behavior based on the food resources available in their environment. They will take on a more solitary or active role depending on their environment.

Types of foraging

thumb|[[Black-headed gulls foraging for various crustaceans and other edibles.]]

Foraging can be categorized into two main types. The first is solitary foraging, when animals forage by themselves. The second is group foraging. Group foraging includes when animals can be seen foraging together when it is beneficial for them to do so (called an aggregation economy) and when it is detrimental for them to do so (called a dispersion economy).

Solitary foraging

Solitary foraging includes the variety of foraging in which animals find, capture and consume their prey alone. Individuals can manually exploit patches or they can use tools to exploit their prey. For example, Bolas spiders attack their prey by luring them with a scent identical to the female moth's sex pheromones. Animals may choose to forage on their own when the resources are abundant, which can occur when the habitat is rich or when the number of conspecifics foraging are few. In these cases there may be no need for group foraging. In addition, foraging alone can result in less interaction with other foragers, which can decrease the amount of competition and dominance interactions an animal deals with. It will also ensure that a solitary forager is less conspicuous to predators. Solitary foraging strategies characterize many of the phocids (the true seals) such as the elephant and harbor seals. An example of an exclusive solitary forager is the South American species of the harvester ant, Pogonomyrmex vermiculatus.

Search behavior

Animals can typically be classified into two categories by their pattern of movement exhibited through foraging behaviors. These categories are "cruise" searchers and "ambush" searchers. Cruise searchers forage by continuously hunting for prey at the outer borders of the area being searched, while ambush searchers forage by sitting and waiting. They remain motionless for long durations as they wait on the prey to pass by, therefore initiating the ambusher to attack. New Caledonian crows that use sticks to get larvae out of trees, and chimpanzees that similarly use sticks to capture and consume termites.

Solitary foraging and optimal foraging theory

The theory scientists use to understand solitary foraging is called optimal foraging theory. Optimal foraging theory (OFT) was first proposed in 1966, in two papers published independently, by Robert MacArthur and Eric Pianka, While the behavior of real animals inevitably departs from that of the optimal forager, optimal foraging theory has proved very useful in developing hypotheses for describing real foraging behavior. Departures from optimality often help 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. In other words, we know from optimal foraging theory that animals are not foraging randomly even if their behavior doesn't perfectly match what is predicted by OFT.

Versions of OFT

There are many versions of optimal foraging theory that are relevant to different foraging situations. These models generally possess the following components according to Stephens et al. 2007;

  • Currency: an objective function, what we want to maximize, in this case energy over time as a currency of fitness
  • Decision: set of choices under the organism's control, An important note here is that group foraging can emerge in two types of situations. The first situation is frequently thought of and occurs when foraging in a group is beneficial and brings greater rewards known as an aggregation economy.

Chimpanzees in the Taï Forest in Côte d'Ivoire also engage in foraging for meats when they can, which is achieved through group foraging. Positive correlation has been observed between the success of the hunt and the size of the foraging group. The chimps have also been observed implying rules with their foraging, where there is a benefit to becoming involved through allowing successful hunters first access to their kills.

Cost and benefits of group foraging

thumb|Female [[lions make foraging decisions and more specifically decisions about hunting group size with protection of their cubs and territory defense in mind.]]

As already mentioned, group foraging brings both costs and benefits to the members of that group. Some of the benefits of group foraging include being able to capture larger prey, being able to capture prey that are difficult or dangerous and most importantly reduction of predation threat.

Theorizing on hominid foraging during the Aurignacian Blades et al. (2001) defined the forager performing the activity to the optimal efficiency when the individual is having considered the balance of costs for search and pursuit of prey in considerations of prey selection. Also in selecting an area to work within the individual would have had to decide the correct time to move to another location corresponding to perception of yield remaining and potential yields of any given area available.

Foraging arena theory

A quantitative model that allows for the evaluation of trade-off decisions that occur in aquatic ecosystems. 'Foraging arenas' are the areas in which a juvenile fish can forage closer to their home while also providing an easier escape from potential predators. This theory predicts that feeding activity should be dependent upon the density of juvenile fishes, and the risk of predation within the area. A balance between the growth and mortality of these juvenile fishes is reliant consequent to the duration of foraging performed by said juvenile fish. These components vary with regards to the habitat.

Group foraging and the ideal free distribution

The theoretical model scientists use to understand group foraging is called ideal free distribution. This is the null model for thinking about what would draw animals into groups to forage and how they would behave in the process. This model predicts that animals will make an instantaneous decision about where to forage based on the quality (prey availability) of the patches available at that time and will choose the most profitable patch, the one that maximizes their energy intake. This quality depends on the starting quality of the patch and the number of predators already there consuming the prey.

See also

  • List of forageable plants (edible by humans)
  • Chesson's index
  • Forage
  • Avian foraging
  • Primate foraging
  • Forage fish
  • Lévy flight foraging hypothesis
  • Scavenging

References

  • The Association of Foragers: An international association for teachers of foraging skills.
  • Forager's Buddy GPS Foraging
  • South West Outdoor Travelers- Wild Edibles, Medicinals, Foraging, Primitive Skills & More
  • Institute for the Study of Edible Wild Plants and Other Foragables
  • Caress, Badiday. (2000), The emergence and stability of cooperative fishing on Ifaluk Atoll, for Human Behavior and Adaptation: an Anthropological Perspective , edited by L. Cronk, N. Chagnon, and B. Iro ns, pp. 437–472.