Behavior of old Japanese monkeys

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Behavior of old Japanese monkeys aged more than 20 years were analyzed both in a free-ranging situation and in captivity, compared with younger animals.(1) Free-ranging situation :1. Old females spent alone more often and were less active than younger ones. Moreover, old females spent their time in grooming other group members less frequently than others. However, they were able to maintain their social ranks similar to their kin relatives, without decreasing in rank. The most important fact is that old females remain social beings even after losing their reproductive abilities.2. The alpha-males (the first ranking male) maintained his rank even though his locomotor ability seemed to be inferior to that of other males, due to his old age. This is because many females tended to follow this old alpha male, without changing into other males.(2) In captivity :1. Four of six old females over 24 years old show irregular menstrual cycles, and the remaining two were in senile sterility.2. Old females tended to show night-time wakefulness and day-time sleepiness more clearly than younger females.3. Taking care behavior of old females toward their offspring was similar to that of younger females.