Sociology of the feeding strategy of Japanese monkeys

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In order to re-examine social behavior of Japanese monkeys in relation to the feeding strategy, studies were conducted at Kinkasan, Takasakiyama, Koshima, and Ryozenyama.1. The monkeys of the Kinkasan troop increased number of food patches to visit in a day, and expanded the duration of feeding time against the food shortage in winter. However, difference was not found for these activities depending on the difference of dominance rank.2. Population parameters of Takasakiyama troops remarkably decreased since 1975 when artificial food supply have been much reduced. This fact shows that food intake directly affects reproductive succes of monkeys. The amount of intake of artificial food showed difference for difference of dominance rank among matri-lines, and females of higher rank showed high reproductive success than those of lower rank. However, the preliminary results showed no difference of the amount of food intake in the forest depending on rank difference.3. Artificial food supply … More for the Koshima troop is reduced minimally, only for the facilitation of observation. The longitudinal change of dominance rank among females was examined in relation to their reproductive success, which was low for lower ranking females among the highest matri-line. The reason for their low reproductive success was analyzed. That is, they were frequently attacked in aggressive interactins, or they showed most unstable dominance rank; they showed drastic drop of dominance rank and high mortality rate after drop of rank. The difference of rank strongly affected their social attitude and their feeding strategy.4. The reproductive success of Ryozenyama troop increased for lower ranking females after division of the mother troop into two, one consisting of higher ranking kins and the other lower ranking. The inferior feeding condition of lower kins must have changed to the same condition with that of the higher kins after the troop division.The present studies indicate that the difference of reproductive success depending on difference of dominance rank is much enhance in the artificial condition, and that it is much reduced in the natural condition. Less