group sizes can lead to decreased group cohesion because time spent grooming is usually impacted by other factors. Consequently, some of these aspects that affect time spent grooming include ecological, phylogenetic, and life history. For example, the article states, "Cognitive constraints and predation pressure strongly affect group sizes and thereby have an indirect effect on primate grooming time". By analyzing past data and studies done about this topic, the authors found that a primate group greater than 40 will face greater ecological problems and, thus, time spent during social grooming is affected. Recent studies regarding chimpanzees have determined the direct correlation of the release of oxytocin to consolatory behavior. This behavior as well as release has been noted in primates such as the Vervet monkey, a primate species that actively engages in social grooming from early childhood to adulthood. Vervet monkey siblings often have conflict over grooming allocation by their mother, yet, grooming remains an activity that mediates tension and is low cost for alliance formation and maintenance. This grooming occurs both between the siblings as well as involving the mother. Recent studies regarding the crab-eating macaques have shown that males will groom females in order to procure sex. One study found that a female has a greater likelihood to engage in sexual activity with a male if he had recently groomed her, compared to males who had not groomed her.[41] Birds Birds engage in allopreening. Researchers believe that this practice builds pair bonds. In 2010, researchers determined the existence of a form of social grooming as a consolation behavior within ravens via a form of bystander contact, whereby observer ravens would act to console a distressed victim via contact sitting, preening, as well as beak-to-beak touching. Horses Horses engage in mutual grooming via the formation of 'pair bonds' where parasites and other contaminants on the surface of the body are actively removed. This removal of foreign material is primarily performed in hard-to-reach areas such as the neck via nibbling. Cattle Allogrooming is a behavior commonly seen in many types of cattle, including dairy and beef breeds. The act of social licking can be seen specifically in heifers to initiate social dominance, emphasize companionship and improve hygiene of oneself or others. This behavior seen in cows may provide advantages including reduced parasite loads, social tension and competition at the feed bunk. It is understood that social licking can provide long