Abstract
This study was designed to examine aggressivity of feral-reared adult Japanese monkeys in the laboratory. Experiments conducted in the present study were as follows : (1) Pairing of males in the non-mating season; (2) Pairing of the males in the mating season; and (3) Exposing another strange male or female to the male pairs in the mating season.
The results showed that aggressive behaviors were hardly observed and intimate behaviors were frequently seen between the males during their non-mating season, while any discernible increase was not seen in the inter-male aggressive behaviors during their mating season (Table 1). Mounting behavior was important in establishing an intimate relationship between the males because it induced virtually the initial non-agonistic physical contact between them (Fig. 1).
The experiment 3 was conducted to examine the effect of another strange animal (stimulus animal) on the aggressivity of the pair males (experimental animals) during their mating season. When the stimulus animal was male, the subordinate experimental animal directed high aggressiveness to him, and this aggression was considered to be “appeal aggression” for the dominant animal paired. On the other hand, when the stimulus animal was female, the dominant male was close to her, and the subordinate male held to stay away from them, while he sometimes received aggression of the dominant male (Fig. 2). Thus it may be conceived that the aggressive behavior of the adult Japanese monkey tends to increase at the polyadic situations. In either of these triadic situations, the subordinate experimental male showed a remarkable skill of adjusting his behavior to the situation in order to make his disadvantageous circumstances improved.
