Physiological Effect of Sweeping Grooming Movements in Macaque Monkey: Preliminary Data

Grooming is a widespread behavior among non-human primates, characterized by rhythmic sweeps and plucking movements of the fingernails directed at addressing skin debris, spots, blemishes, ectoparasites or vegetation trapped in the fur [1]. Self-grooming is directed toward the individual’s own body (primarily those accessible parts, such as the arms and the legs), while allogrooming is carried out on others’ body parts either inaccessible or invisible to self-grooming [2,3]. All non-human primates devote a significant amount of time to grooming other individuals, with studies related to allogrooming among semi-free-ranging monkeys in their own natural habitat hypothesizing that this behavior has not only hygiene functions [4-11], but also that it is the most common affiliative relationship and social strategy employed to create and maintain relationships and reliable alliances against predators [12]. Moreover, allogrooming enhances relaxation and a sense of security [13], and reduces anxiety levels [4,14] by means of the decrement of the heart rate when receiving grooming [15], and of reduced cortisol levels during both passive [16] and active grooming [17].