Foraging

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. Foraging theory predicts that the decisions that maximize energy per unit time and thus deliver the highest payoff will be selected for and persist. Key words used to describe foraging behavior include resources, the elements necessary for survival and reproduction which have a limited supply, predator, any organism that consumes others, prey, an organism that is eaten in part or whole by another, and patches, concentrations of resources.
Behavioral ecologists first tackled this topic in the 1960s and 1970s. Their goal was to quantify and formalize a set of models to test their null hypothesis that animals forage randomly. Important contributions to foraging theory have been made by:

Eric Charnov, who developed the marginal value theorem to predict the behavior of foragers using patches;
Sir John Krebs, with work on the optimal diet model in relation to tits and chickadees;
John Goss-Custard, who first tested the optimal diet model against behavior in the field, using redshank, and then proceeded to an extensive study of foraging in the common pied oystercatcher.
Factors influencing foraging behavior

Several factors affect an animal's ability to forage and acquire profitable resources.

Learning

is defined as an adaptive change or modification of a behavior based on a previous experience. 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.
In nonhuman primates, young individuals learn foraging behavior from their peers and elders by watching other group members forage and by copying their behavior. 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. Forebrain size has been associated with learning behavior. Animals with larger brain sizes are expected to learn better. A higher ability to innovate has been linked to larger forebrain sizes in North American and British Isle birds according to Lefebvre et al.. 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.
Another measure of learning is spatio-temporal learning, which refers to an individual's ability to associate the time of an event with the place of that event. This type of learning has been documented in the foraging behaviors of individuals of the stingless bee species Trigona fulviventris. Studies showed that T. fulviventris individuals learned the locations and times of feeding events, and arrived to those locations up to 30 minutes before the feeding event in anticipation of the food reward.

Genetics

Foraging behavior can also be influenced by genetics. The genes associated with foraging behavior have been widely studied in honeybees with reference to the following; onset of foraging behavior, task division between foragers and workers, and bias in foraging for either pollen or nectar. 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 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.
Some behaviors are more dominant than others. In a study using fruit fly larvae, there were two types of foraging strategies: rovers and sitters. 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 gene. During the study, homozygous strains were produced by crossing the rovers with rovers and sitters with sitters. Using the method of hybridization - crossing rovers with sitters - all of the offspring displayed the rover foraging behavior, thus demonstrating that it is an allele of complete dominance.

Presence of predators

The presence of predators while a animal is foraging affects its behaviour. In general, foragers balance the risk of predation with their needs, thus deviating from the foraging behaviour that would be expected in the absence of predators. An example of this balanced risk can be observed in the foraging behavior of the amphipod Ampithoe longimana.

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.

Interactions with environment

Interactions with the environment significantly influence foraging behavior by dictating the availability of resources, the competition among others, the presence of predators, and the complexity of the landscape. These factors can affect the strategies animals use to find food, the risks they're willing to take, and the efficiency of their foraging patterns. For example, in environments with abundant resources, foragers may adopt less risky and energy-efficient strategies. Conversely, in resource-scarce or high-risk environments, more complex and risky foraging behaviors may evolve. 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

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 and when it is detrimental for them to do so.

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 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.

Tool use in solitary foraging

Some examples of tool use include dolphins using sponges to feed on fish that bury themselves in the sediment, 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 was first proposed in 1966, in two papers published independently, by Robert MacArthur and Eric Pianka, and by J. Merritt Emlen. This theory argues that because of the key importance of successful foraging to an individual's survival, it should be possible to predict foraging behavior by using decision theory to determine the behavior that an "optimal forager" would exhibit. Such a forager has perfect knowledge of how to optimize energy intake per unit of feeding time, based on the assumption that natural selection shapes foraging behavior to maximize the rate of energy gain. 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.