Case study of a one‐sided attack by multiple troop members on a nontroop adolescent male and the death of Japanese macaques (Macaca fuscata)

Abstract

An adolescent wild male Japanese macaque (Macaca fuscata), following Kinkazan A troop, was attacked one-sidedly by multiple members of the troop. The victim was identified as PI, and was estimated to be seven+/-one year old. The aggressive interaction was recorded by video camera until the end. Although at least 16 troop members approached PI more than once, only three males (one adult, two adolescents) of A troop attacked him. PI kept crouching throughout the attack, then escaped to the shore and dived into the sea. The interaction continued for more than one hour. PI was found dead a few hours after the end of interaction. The damage caused by the assailants was not the direct cause of PI's death; it was due to hypothermia caused by drifting in the sea. PI's life history was reconstructed from past records. PI was a normal adolescent male who migrated from an all-male group around B1 troop and started ranging around A troop. The aggressive interaction is believed to be a typical example of conflict between troop males and a nontroop male. The interaction period was very long compared with previous reports on such conflicts among Japanese macaques. PI kept crouching in open areas, exposing himself as a potential competitor for the resources of the troop, and did not show any submissive or reconciliatory behavior toward the troop males. This may be why the troop males did not stop the attack.

Within-Population Variations in Home Range Use and Food Patch Use of Japanese Macaques: A Perspective of Intergroup Hostility

“…First, macaques in the smaller coastal group reduce the risk of injury or death along the border by being in proximity with a large number of group members [Wilson and Wrangham, 2003]. It was reported that lone animals were injured or killed by out-group members, even in species forming cohesive groups [Mech, 1994;Gros-Louis et al, 2003;Shimada et al, 2009]. Second, macaques in the smaller coastal group detect and run away from other groups more quickly along the border because more eyes and ears become available to scan the surroundings [Beauchamp, 2015].…”

Effects of proximity and activity on visual and auditory monitoring in wild Japanese Macaques

“…Separation from group members has several disadvantages, such as increased risk of predation and aggression from conspecifics of other groups [Goodall, 1986;Shimada et al, 2009]. However, each group is usually composed of individuals of different age-sex classes whose requirements and abilities differ [van Schaik & van Noordwijk, 1986].…”

“…In some populations, including the population observed for this study, intergroup relationships are agonistic. Severe aggression toward solitary individuals has also occasionally been observed [Shimada et al, 2009]. Thus, the maintenance of group cohesiveness provides an advantage through increased feeding efficiency, whereas leaving a group is disadvantageous because of aggression from conspecifics and intergroup competition.…”

Initial experience with the cardiva Boomerang™ vascular closure device in diagnostic catheterization

“…Many primate species form cohesive groups whose members usually travel together to increase feeding efficiency and to avoid predation [Kappeler & van Schaik, 2002; Kinzey & Cunningham, 1994]. Separation from group members has several disadvantages, such as increased risk of predation and aggression from conspecifics of other groups [Goodall, 1986; Shimada et al, 2009]. However, each group is usually composed of individuals of different age–sex classes whose requirements and abilities differ [van Schaik & van Noordwijk, 1986].…”

“…In some populations, including the population observed for this study, intergroup relationships are agonistic. Severe aggression toward solitary individuals has also occasionally been observed [Shimada et al, 2009]. Thus, the maintenance of group cohesiveness provides an advantage through increased feeding efficiency, whereas leaving a group is disadvantageous because of aggression from conspecifics and intergroup competition.…”