Formosan macaques were observed to collect data on intergroup encounters, the strategies of male and female and the factors which influence inter-group dominance relationships. Four hypotheses exist to explain the strategies of male and female in inter-group encounter, including female resource defense, male mate defense, male resource defense and male mate attraction via infanticide. Behavioral observations were recorded from March 2008 to March 2009. Data collections included scan sampling and focal sampling of troop members which participated in encounter, containing their sex, age, rank and behavior. Duration of inter-group interaction and distances between two troops were also recorded. There is a significant positive relationship between chance of winning and troop number (AM+AF+SAM), and this chance of winning is higher than 50% when troop size exceeded 30. There is also a significant linear regression between weight win¡]main group and branch group¡^and troop number , but chance of weight win in some troops is higher than 90% when troop size is only between 20 to 30. Approach, line-up, displace and be-displaced have significant correlation with troop size type. Large troops displayed higher displace (65%), line-up (6%) and approach (28%) than other type of troops, and small troop were easily displaced by other type of troops (60%). Aggressive behavior also has significant correlation with mating season significantly; troops of Formosan macaques display more aggressive behavior in mating season (70%) than in non-mating season (41%). Troops of Formosan macaques display higher approach¡]33%¡^ and displace (93%) when troops encounter with all male troop than with bisexual troop. Inter-group dominance relationships exist among main group and branch group which newly split of Formosan macaques. But there is uncertain inter-group dominance relationships between main group and branch group which split early for the difference of maternal dominance hierarchies, variation of troop numbers, and the character of central males. Adult male and female Formosan macaques adopt different strategy in inter-group encounter. Adult female Formosan macaques participated (8.62%, n=8) and displayed aggressive behavior (3.66%, n=8) in more food-related encounter than in non-food-related encounter, so female resource defense hypothesis is supported. Adult male Formosan macaques display higher aggressive behavior (7.92%, n=23) significantly than adult female and sub-adult male in inter-group encounter, and the target of aggression is higher for males than for females. Adult and sub-adult male Formosan macaques display higher aggressive behavior in mating season significantly than in non-mating season. So male mate defense hypothesis is also supported. This study provides support for the male resource defense hypothesis. Adult male Formosan macaques would defend food resource directly and indirectly. Besides, frequencies of participation and aggression in low ranking adult male Formosan macaques are higher than high ranking ones to exchange mating opportunity.

<p>Only in primates is permanent male-female association the most widespread social structure of all. The continuous presence of resident males in the social group can have significant impacts on female fitness, both in forms of costs and benefits. In this study I investigate particular short-term benefits and costs of resident males to females in a population of ursine colobus (<em>Colobus vellerosus</em>). I hypothesise that for females permanent association with males result in certain benefits and certain costs, exceeding those provided or imposed by other females. The results indicate that female derive greater benefits from males than from females during intergroup encounters and in the form of vigilance since males were the main participants in intergroup encounter and were more vigilant than females. I could not confirm any type of behaviour employed by resident males that is costly to females. However, the rarity and subtleness of some costly male behaviours imply that more data is needed before making a conclusion on their absence or occurrence in this population and I purpose that herding behaviour could occur at my study site. Moreover, multi-male groups (MM-groups) showed higher rates of vigilance than single-male groups (SM-groups) and had a tendency to experiencing fewer intergroup encounters than SM-groups. I interpret the former as a result of the demanding social conditions in the MM-groups. The latter indicate that females may benefit from MM-group living through a decrease in intergroup encounters.</p>

Only in primates is permanent male-female association the most widespread social structure of all. The continuous presence of resident males in the social group can have significant impacts on female fitness, both in forms of costs and benefits. In this study I investigate particular short-term benefits and costs of resident males to females in a population of ursine colobus (Colobus vellerosus). I hypothesise that for females permanent association with males result in certain benefits and certain costs, exceeding those provided or imposed by other females. The results indicate that female derive greater benefits from males than from females during intergroup encounters and in the form of vigilance since males were the main participants in intergroup encounter and were more vigilant than females. I could not confirm any type of behaviour employed by resident males that is costly to females. However, the rarity and subtleness of some costly male behaviours imply that more data is needed before making a conclusion on their absence or occurrence in this population and I purpose that herding behaviour could occur at my study site. Moreover, multi-male groups (MM-groups) showed higher rates of vigilance than single-male groups (SM-groups) and had a tendency to experiencing fewer intergroup encounters than SM-groups. I interpret the former as a result of the demanding social conditions in the MM-groups. The latter indicate that females may benefit from MM-group living through a decrease in intergroup encounters.