Behavior of snow monkeys hunting fish to survive winter

Abstract

Japanese macaques, Macaca fuscata, of Kamikochi in the Japanese Alps endure one of the coldest and harshest environments during winter when scarcity of food puts them at risk. However, various behaviors have evolved to mitigate potential mortality. These macaques typically eat bamboo leaves and the bark of woody plants in winter, but our previous study using the feces of Japanese macaques collected in the winter and DNA metabarcoding analysis revealed conclusively for the first time consumption of riverine benthos and brown trout. In this paper, we investigate how Japanese macaques hunt fish and collect these riverine biota by extensively observing their behavior, including the use of infrared sensor cameras. Many researchers have tracked Japanese macaques as part of behavioral and ecological studies, but previously the techniques by which Japanese macaques capture swimming fish has not been documented. Herein, for the first time we consider how novel macaque foraging behavior traits have evolved to secure valuable animal protein for winter survival when food resources are scarce.

Figure 1

Research area in Kamikochi for observation of Japanese macaques’ fishing behavior. Infrared sensor cameras were set in three places marked with star symbols (St. 1–2, 5). During the behaviors observation at the three sites (St. 2–4), fishing and/or collecting aquatic benthos were observed and recorded as video images. (A) Research area in this study (B) A troop of Japanese macaques foraging aquatic benthos along the Azusa River in the Myojin-ike Pond area (St. 4). (C–E) A series showing behavior of a monkey catching swimming fish at station 3. (F–H) A series showing behavior of a monkey catching a swimming fish and predation at station 2.