Evolution.

Society for Experimental Biology

Date:: 1953

Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Evolution. Source: Wellcome Collection.

451/484 (page 419)

SOCIAL BEHAVIOUR AND PRIMATE EVOLUTION 42I closely associated than the second most dominant male and the third one in the male dominance hierarchy. During oestrus, females seek the closest possible spatial association with responsive males, so that the short distance separating the two animals, and the continuance of this close association are reliable indicators of oestrus in the female. (Carpenter, 19426.) When these two social forces occur together, the region close to a domi¬ nant male where the most attractive oestrous females are situated is also the region of maximum conflict for subordinate males subject to the dominance of the overlord. This region in its simplest form is trigonal, consisting of the overlord, an oestrous female, and a subordinate male. Within such a group of individuals it should be possible to observe that in the movement of the group as a whole, the spatial relations will be main¬ tained approximately constant in response to the attraction exerted for the males by the female, counterbalanced in the case of the subordinate animals by threat from the dominant male. Evidence of this was provided by the following observation which was made during studies of a free-ranging macaque colony. Four adults were close to the edge of an enclosure on our arrival at this colony. The social status of these individuals was easily recognized. The situa¬ tion of this group is illustrated in Text-fig. 3. The configuration shown in A was evidently one of equilibrium. The dominant male and a female showing maximal sexual skin were together copulating at intervals. A young male was in the vicinity watching this, while a pregnant female was grooming herself. A peanut was then oflered as indicated in В (by a cross) through the bars. Female i immediately came to the bars, male i making no attempt to secure the peanut. Male 2 moved towards the nut and towards female i. Female 2 was greatly interested and came to the bars. Im¬ mediately the situation became unstable. Female 2 refused to come nearer the peanut intimidated by the more dominant female. Male i stood up and threatened male 2 who had moved to a position very close to female i. The nearer female i moved towards the peanut the farther away from it moved female 2. The two oppositional vectors shown in В were clearly demonstrated by the behaviour of these animals, each watching the other closely throughout. Immediately equilibration occurred. Male 2 moved back towards the centre of the enclosure, stopping at about the same distance from male i as before. Male i approached female i who had by now obtained, and was eating, the peanut. Female 2 moved around the perimeter for several yards before moving to her original position. During the entire period of observation, the rapid movements of the eyes of the animals never ceased, and reached a peak just before the situation became once more stable, after the changes of position had ceased.