A junior high school Japanese-language textbook to be used beginning in the 2012 academic year will contain an article authored by Assistant Professor Yamato Tsuji from the Primate Research Institute, which is titled "Gleaning by Deer: From My Field Note Records" (pp. 118-125, Mitsumura Tosho Publishing Co., Ltd.).
The article in the textbook is about his research on the relationship that exists between Japanese macaques (monkeys) and sika deer on Kinkasan Island in Miyagi Prefecture, which he started after he happened to see a deer collecting and eating plants dropped by a monkey up in a tree while he was investigating the diet of Japanese macaques.
Japanese macaques living up in trees and sika deer living down on the ground had been previously considered to have no relationship with each other, but research by Assistant Professor Tsuji and his colleagues has revealed the possibility that monkeys up in trees may have beneficial effects on sika deer because they drop nutritious food from above in seasons when there is little food on the ground. Similar observation results have been reported from other parts of Japan since his report was published. In particular, a flock of deer on Yakushima Island in Kagoshima Prefecture track monkeys all day long as they go around eating food up in trees. Also, overseas in various regions throughout Southeast Asia and Africa, we sometimes see a deer or antelope going under a tree, where a monkey is present, and start gathering dropped food. These relationships between primates and mammals living on the ground are not accidental occurrences but should be considered a part of the daily life of the two species living in a common environment. It is fun to imagine what the two species of animals think of each other during the gleaning time. As he writes in the article, it is not known yet how much monkeys contribute to the life of sika deer. We will learn about their relationship more clearly through future research.
The first page of the article in a junior high school Japanese-language textbook (Mitsumura Tosho Publishing Co., Ltd.)