Social grooming

Social grooming is a behaviour in which social animals, including humans, clean or maintain one another's body or appearance. A related term, allogrooming, indicates social grooming between members of the same species. Grooming is a major social activity, and a means by which animals who live in close proximity may bond and reinforce social structures, family links, and build companionships. Social grooming is also used as a means of conflict resolution, maternal behaviour and reconciliation in some species. Mutual grooming typically describes the act of grooming between two individuals, often as a part of social grooming, pair bonding, or a precoital activity.Mutual grooming in poniesThree macaques grooming one anotherSocial grooming in hyacinth macawsFemale budgerigar preening the male (video)One lion grooming anotherAllopreening in Yellow-billed BabblerBonnet macaque allogrooming while infant suckles Social grooming is a behaviour in which social animals, including humans, clean or maintain one another's body or appearance. A related term, allogrooming, indicates social grooming between members of the same species. Grooming is a major social activity, and a means by which animals who live in close proximity may bond and reinforce social structures, family links, and build companionships. Social grooming is also used as a means of conflict resolution, maternal behaviour and reconciliation in some species. Mutual grooming typically describes the act of grooming between two individuals, often as a part of social grooming, pair bonding, or a precoital activity. There are a variety of proposed mechanisms by which social grooming behavior has been hypothesized to increase fitness. These evolutionary advantages may come in the form of health benefits including reduced disease transmission and reduced stress levels, maintaining social structure, and direct improvement of fitness as a measure of survival. Social grooming behavior has been shown to elicit an array of health benefits in a variety of species.  For example, group member connection has the potential to mitigate the potentially harmful effects of stressors. In macaques, social grooming has been proven to reduce heart rate. Social affiliation during a mild stressor was shown to correlate with lower levels of mammary tumor development and longer lifespan in rats, while lack of this affiliation was demonstrated to be a major risk factor. Grooming has also been shown to play an integral role in reducing tick load in wild baboons (Papio cynocephalus). These ectoparasitic ticks carry the potential to act as vectors for the spreading of disease and infection by common tick-borne parasites such as haemoprotozoan. Baboons with lower tick loads show decreased occurrence of such infections and display signs of greater health status, evidenced by higher hematocrit (packed red cell volume) levels. One of the most critical functions of social grooming is to establish social networks and relationships. In many species, individuals form close social connections dubbed “friendships.” In primates especially, grooming is known to have major social significance and function in the formation and maintenance of these friendships. Grooming networks in black crested gibbons have been proven to contribute greater social cohesion and stability. Groups of gibbons with more stable social networks formed grooming networks that were significantly more complex, while groups with low stability networks formed far fewer grooming pairs. In meerkats, social grooming has been shown to carry the role of maintaining relationships that increase fitness. In this system, researchers have observed that dominant males receive more grooming while grooming others less, thereby indicating that less dominant males groom more dominant individuals to maintain relationships. In addition to primates, animals such as deer, cows, horses, vole, mice, meerkats, coati, lions, birds, bats also form social bonds through grooming behavior. Social grooming is critical for vampire bats especially, since it is necessary for them to maintain food-sharing relationships in order to sustain their food regurgitation sharing behavior. Social grooming relationships have been proven to provide direct fitness benefits to a variety of species. In particular, grooming in yellow baboons (Papio cynocephalus) has been studied extensively, with numerous studies showing an increase in fitness as a result of social bonds formed through social grooming behavior. One such study, which collected 16 years of behavioral data on wild baboons, highlights the effects that sociality has on infant survival. A positive relationship is established between infant survival to one year and a composite sociality index, a measure of sociality based on proximity and social grooming. Evidence has also been provided for the effect of sociality on adult survival in wild baboons. Direct correlations between measures of social connectedness (which focuses on social grooming) and median survival time for both female and male baboons were modeled. Social bonds established by grooming may provide an adaptive advantage in the form of conflict resolution and protection from aggression. In wild savannah baboons, social affiliations are shown to augment fitness by increasing tolerance from more dominant group members and increasing the chance of obtaining aid from conspecifics during instances of within-group contest interactions. In the yellow baboon, adult females form relationships with their kin, who offer support during times of violent conflict within social groups. In Barbary macaques, social grooming results in the formation of crucial relationships among partners. These social relationships serve to aid cooperation and facilitate protection against combative groups composed of other males, which can oftentimes cause physical harm. Furthermore, social relationships have also been proven to decrease risk of infanticide in several primates. Altruism, in the biological sense, refers to a behavior performed by an individual that increases the fitness of another individual while decreasing the fitness of the one performing the behavior. This differs from the philosophical concept of altruism which requires the conscious intention of helping another. As a behavior, altruism is not evaluated in moral terms, but rather as a consequence of an action for reproductive fitness. It is often questioned why the behavior persists if it is costly to the one performing it, however, Charles Darwin proposed group selection as the mechanism behind the clear advantages of altruism. Social grooming is considered a behavior of facultative altruism- the behavior itself is a temporary loss of direct fitness (with potential for indirect fitness gain), followed by personal reproduction. This tradeoff has been compared to the Prisoner's Dilemma model, and out of this comparison came Robert Trivers reciprocal altruism theory under the title 'tit-for-tat'. In conjunction with altruism, kin selection bears an emphasis on favoring the reproductive success of an organism's relatives, even at a cost to the organism's own survival and reproduction. Because of this, kin selection is an instance of inclusive fitness, which combines the number of offspring produced with the number an individual can ensure the production of by supporting others, such as siblings. r B > C {displaystyle rB>C}