Hideyuki Ohsawa

Population Dynamics of Japanese Monkeys with Special Reference to the Effect of Artificial Feeding

Population dynamics of Japanese monkeys (Macaca fuscata) have been studied at Mt. Ryozen, central Japan, between 1969 and 1980. The troop had been artificially fed until August 1973 and, since then, has been living in its natural habitat without artificial feeding. Increase in body weight, primiparous age, age-specific natality, survivorship and mortality, population and biomass growth rate, and age of disappearance of young males were compared between the two study periods, with and without artificial feeding. Comparison of population parameters in each study period was also done between social classes, central and peripheral. As shown, in table VII, it was revealed that artificial feeding was an important factor in population growth and, furthermore, that this effect was mainly on the kin-groups of the central class of the troop. In the natural habitat without artificial feeding most of the population parameters showed almost the same figure for kin-groups of central and peripheral classes.

Social organization of gelada baboons : social units and definitions

This paper aims to clarify terminological differences that have arisen between two different field studies of gelada baboons (Theropithecus gelada). First, a comparison of age classifications is made to show the physical correspondences between the two sets of classes. Second, the social system of the gelada baboon is outlined and the terms used to refer to the components of this system are defined and clarified. Attention is drawn to the complex structure of gelada society and to the relationship between the superficially similar social systems of the gelada and the hamadryas baboon.

Mating strategy and reproductive success of male patas monkeys (Erythrocebus patas)

Mating behavior and paternity of offspring of wild patas monkeys were studied at Kala Maloue National Park, Cameroon. Observation of patas groups over three years revealed that multi-male situations occurred after takeover of the position of a resident male. Direct observation of behavior showed that resident males (harem males) occupied only 31% of mating in multi-male situations and 100% in one-male situations. DNA-typing revealed that resident males sired two of four of infants in the one-male situation and four of five in the multi-male situation. Under the two years cycle of the one-male situation and the multi-male situation, calculation shows that resident males sired more offspring than sneakers both in observation and paternity testing. Sneak mating occurred during both one-male and multi-male situations, and resident males performed compensatory mating, with dilution of sneaker sperm; these activities explain the discrepancy found between observation of mating and results of paternity discrimination.

Male dominance rank and reproductive success in an enclosed group of Japanese macaques: with special reference to post-conception mating

The mating behaviour and reproductive success of male Japanese macaques (Macaca fuscata) were studied in relation to the female sexual cycles, which were monitored from the plasma profiles of gonadotropins and ovarian hormones. Based on observations of the mating behaviour during four successive mating seasons and paternity identification by DNA fingerprinting in 35 out of 37 offspring born in the subsequent birth seasons, the correlations between (1) male dominance rank and timing of mating, and (2) male dominance rank and reproductive success were examined. The results may be summarized as follows. (1) The number of copulations with ejaculation by any male was positively correlated with the male dominance rank, but not with the identified numbers of offspring fathered by each male. (2) Males could not choose ovulatory females as mating partners: the number of copulations with ejaculation with females during ovulatory weeks was not related to the males rank. Monopolized copulations in consortship were mostly observed between high-ranking males and non-lactating parous females after conception. (3) Paternity testing showed that the male copulating most frequently with a female was not the identified father in 11 out of 15 cases. Prediction of the fathers of offspring was difficult even from the number of copulations occurring at around the estimated time of ovulation. An adaptive explanation of these correlations is discussed.

Population dynamics of japanese macaques at ryozenyama: III. Female desertion of the troop

Troop desertions by females which were observed in Japanese macaque troops at Ryozenyama between 1969 and 1978 are described and the factors which drive females out from the troop are discussed with reference to the troop desertion by males and to the social structure of Japanese macaques. There were 14 cases and altogether 22 female deserters of 5 or more years old; ratio(%) of frequency of the female desertion to the total number of females was 9.48 a year. Female deserters of less than 10 years old had no mother in the troop and belonged to rather isolated kin-groups on the periphery of the troop prior to desertion except for those who deserted it with their mothers. Old deserters were not always very peripheral ones and some of them cut kinship bonds when doing so.Many female deserters were found in or near the moving range of the original troop and some came back to it. They were easily accepted without antagonism and they were expected to retain the potential membership of their natal troop. From these facts it is clear that the basic organization of the troop of Japanese macaques is the kin-group and the animals are bound by the head of the kin-group or elder mothers but that intra-kinship social bonds as well as inter-kinship bonds gradually weaken in old females.