In ethology and evolutionary biology, group living is defined as individuals of the same species (conspecifics), maintaining spatial proximity with one another over time with mechanisms of social attraction.
[2] Therefore, species that form groups through social interaction will result in a group of individuals that gain an evolutionary advantage, such as increased protection against predators, access to potential mates, increased foraging efficiency and the access to social information.
[7] Some examples of this happens during mating, parental care of their offspring, or even aggregations of conspecifics to an area to exploit resources of food or shelter.
[9][1] There have been multiple different hypotheses proposed to explain how group living evolved in animals.
[1] Other studies argue that the main driving force of the evolution of social grouping is phylogenetic inertia alongside ecological pressure.
When individuals form a group, they can more effectively locate high quality resources in their environment.
[1] The cues and signals produced thus helps individuals of a group discriminate between low- and high-quality resources.
[12][13] In some species, for instance the forest tent caterpillar (Malacosoma disstria), foraging behaviors change depending on food source.
[14] Another advantage of living in a group is seen in many prey species in their ability to increase defenses against predatory animals.
It is important to note however; this effect only occurs where predators are unable to capture all individuals in a group.
[1] All individuals in a large group however, may not benefit from the dilution effect, and thus the selfish herd theory was developed.
The selfish herd theory states that individuals in the periphery of a group is more likely to be preyed upon than those in the center of the group[17] It is hypothesized that reproductive success of a female is determined by the number of eggs she can produce, while reproductive success of a male is determined by the number of females he mates with.
Alongside this, living in a group allows for higher reproductive success as individuals have access to a greater number of potential mates, and the possibility to choose between them.
The reduction in energy gain seen in females of the larger group also then negatively affected the development rates of any infant offspring.
Therefore, some individuals may actually show reduced reproductive success while living in a group despite the increased presence of potential mates.
In contrast, individuals in groups smaller than their optimum have increased stress levels arising from inadequate defense from predators.
[29] Offspring resulting from inbreeding have an increased chance to be affected by recessive or deleterious traits, thus reducing its survivability and ability to reproduce.