Japanese monkeys living in the Okoppe Basin of the Shimokita Peninsula: The second report of the winter follow-up survey after the aerial spraying of herbicide

Abstract

In regard to a late winter ecological survey of the Japanese monkeys living in the Okoppe Basin and to investigate the aftereffects of the herbicide which was sprayed aerially by the Aomori Regional Forestry Office, the following results were obtained: Troop Z, one of the three troops found in December, moved restrictively around the upper basin of the Okoppe River during this survey period, which area had been strongly influenced by the spraying. The movements of troop Z could be traced throughout this period and the distance of movement per day, the sleeping places, the population, and the social composition were confirmed. The nomadic range was 2.5 square km, equal to only 15.6% of that of December. The monkeys of troop Z fed mainly the bark and buds of trees. The poisonous residue remaining in the bark and buds is ingested by pregnant female monkeys through feeding and may exert some influence upon the fetus.