Kazuo Wada

Seasonal home range use by Japanese monkeys in the snowy Shiga heights

Between December 1974 and November 1975 (157 days), it was found that seasonal home range changes in the Shiga C troop were closely related to food changes, vegetation, and the existence of neighbouring troops. The detailed points clarified may be summarized as follows: (1) The seasonal home range sizes from winter to autumn were 1.23 km2, 1.46 km2, 1.69 km2, and 1.21 km2, respectively, and the annual size was 3.66 km2; (2) The food changed from bark and buds of trees in winter to young leaves and stems of grasses and trees in spring and summer, and fruits in autumn; (3) Each home range clearly changed according to the phenology of the plants used as food at each season; (4) The food abundance for the monkeys was extremely poor in winter, relatively poor in summer, plentiful in spring, and the best in autumn; and (5) The Shiga C troop and the neighbouring Shiga B2 troop overlap in their home ranges in spring and autumn, but are separated during winter and summer.

Habitat utilization by wintering Japanese monkeys (macaca fuscata fuscata) in the Shiga heights

The detailed habitat utilization of the Shiga B2 troop was studied in winter. The following results were obtained. (1) The roosting site distribution was limited to the Yokoyugawa valley. (2) The measured home range size was 1.99 km2, which was greater than the 1.23 km2 of larger population size of the Shiga C troop. (3) The daily travel distance ranged from 0 to 1,825 m (mean 646 m). (4) The pendulum cycle of troop movement is composed of two types: wandering and tripping. The daily travel distance in tripping was much longer than that in wandering. (5) The utilization rate of the home range was assessed according to the total length of the travelling course per grid square. Highly utilized areas in the home range were found along the Yokoyugawa valley without using areas far from the valley. (6) Diurnal activity was influenced by climate, although it was difficult to establish any clear daily rhythm. (7) The food items amounted to 39 species. (8) Distribution of densely utilized sites of food resources almost coincided with those of resting sites. (9) The reasons for the use of the complete home range by the B2 were also discussed.

Determination of age in the Japanese monkey from growth layers in the dental cementum

The teeth of 14 Japanese monkeys (Macaca fuscata) were examined to establish an exact method of determining age by histological observation of dental cementum. The cementum showed annual growth layers, which were especially remarkable in the incisor root and in the molar cementum deposited at the junction of the roots. The layer of cementum formed in winter appears as a dark layer in stained sections and as a translucent layer in unstained ground sections. In the incisor the first dark and light layers are formed at the age of three years, whereas in the molar they do not appear at a definite age. The layers are thick and clear in the upper medial incisor. As a result, the age of a Japanese monkey can be determined by adding two to the number of dark layers and an outer light layer.It is interesting that the formation of the cementum of the first molar begins a few years after its eruption. The relation between this fact and the pressure of occlusion is discussed.

Dietary adaptations of temperate primates : comparisons of Japanese and Barbary macaques

Habitat, diet and leaf chemistry are compared between Japanese and Barbary macaques to reveal the similarities and differences in dietary adaptations of temperate primates living at the eastern and western extremes of the genus Macaca. Tree species diversity and proportion of fleshy-fruited species are much higher in Japan than in North Africa. Both species spend considerable annual feeding time on leaves. Japanese macaques prefer fruits and seeds over leaves, and Barbary macaques prefer seeds. These characteristics are adaptive in temperate regions where fruit availability varies considerably with season, since animals can survive during the lean period by relying on leaf and other vegetative foods. The two species are different with respect to the higher consumption of herbs by Barbary macaques, and the leaves consumed contain high condensed and hydrolysable tannin for Barbary but not for Japanese macaques. Barbary macaques supplement less diverse tree foods with herbs. Because of the low species diversity and high tannin content of the dominant tree species, Barbary macaques may have developed the capacity to cope with tannin. This supports the idea that digestion of leaves is indispensable to survive in temperate regions where fruit and seed foods are not available for a prolonged period during each year.

A new approach to evaluating troop deployment in wild Japanese Monkeys

In winter when the mountain slopes are covered with deep snow, it is easy to obtain quantitative data on the two-dimensional deployment of members of a troop of wild Japanese monkeys. We observed the deployment of a troop on a slope from the opposite side of a river. The deployment patterns, evaluated on the basis of the relative distance from the central point (centroid) of the troop, were different for each sex and age category. Adult females, infants, and 1-year-olds tended to be grouped together and were concentrated near the center of the troop. On the other hand, adult males were randomly spaced. These tendencies suggest that the deployment reflects the social structure of the duplicate concentric-circle model originally proposed by J. Itani (1954).

Long-term changes in the winter home ranges of Japanese monkeys in the Shiga heights

In the home ranges of the monkeys, the densely utilized food sites (densely utilized sites of food resources ofWada andTokida, 1981) varied over a period of ten years. The Shiga B2 troop changed both its densely utilized food sites and the kinds of tree mostly eaten within the same home range, whereas the Shiga C troop transferred to a new home range. The home range transition of the C troop was influenced by both food deficiencies and the existence of the B2 troop. Based on these facts, it can be said that two types of long-term home range utilization were distinguishable.

One-trial long-lasting food-aversion learning in wild Japanese monkeys (Macaca fuscata)

We examined how Japanese monkeys in the wild formed an aversion to food which had been paired with poison. Ten monkeys of various ages and both sexes were chosen as subjects from 105 members of the Shiga-A1 troop at Jigokudani in Shiga Heights in Japan. We gave almond nuts to each subject. Once a monkey ate 10-20 almond nuts, he was captured and moved into an injection cage. Seven experimental subjects were injected intravenously with cyclophosphamide (20 mg/kg). Three control subjects received the same treatment except that they were injected with physiological saline. About 1 hour later, all subjects were released into the troop. The tests for conditioned aversions were conducted during the next 2 days. In the tests, the experimental subjects would not eat almond nuts, while the control subjects showed no hesitation in eating them. Five of the seven experimental subjects retained perfectly the aversion to almond nuts in tests conducted 1 month and 3 months later. The one-trial long-lasting food-aversion learning shown by the wild Japanese monkeys is discussed in terms of their feeding strategy. These results also suggest that food-aversion conditioning has potential as a nonlethal method for controlling crop-raiding monkeys.

Shape of, and body direction in, huddles of Japanese macaques (Macaca fuscata) in Arashiyama, Japan

We studied huddles of Japanese macaques (Macaca fuscata) in the Arashiyama E troop at the “Arashiyama Monkey Park, Iwatayama” of Kyoto, central Japan. The macaques made physical contact with other individuals and formed huddles when the air was cold. The 99–101 adult females and 26–36 adult males in the study troop formed 345 huddles during 42 scan samples in the winter of 2001 and 376 huddles during 52 scan samples in the winter of 2002. The average size of huddles was 2.3 (range 2–7) individuals. Males huddled less frequently than females. Maternal kin-related dyads formed 2-female huddles more frequently than unrelated dyads. Choice of huddling partners might restrict the size of huddles. The most frequently observed 3 and 4-member huddles were triangular and diamond-shaped. Macaques usually huddled ventro–ventrally, ventro–laterally, and ventro–dorsally. A third individual frequently placed the ventral part of its body against the first individual and simultaneously put the lateral part of its body against the second individual, so that the 3 individuals formed a triangular huddle. This behaviour indicates that Japanese macaques choose their position and body direction in the huddle to reduce the area of body surface exposed to the air, thereby conserving body heat.

Identifying inter-individual social distances in Japanese monkeys

Abstract Japanese monkeys (Macaca fuscata) appear to recognize three types of inter-individual distances: (1) intimate distance less than 1 m, (2) personal distance 1–3 m and 1–5 m (close and far phase), and (3) social distance 3 or 5 m variable outer limit. The boundary between intimate and personal distance, 1 m, works as a protective sphere around individuals. Because personal distance reflects an existence of individuals, we defined this distance as a basic distance among three types. We reviewed related studies and found that Japanese monkeys change their inter-individual distances according to social and ecological circumstances. Additionally, we suggest that these three types of distances can be applicable across the Macaca species.

Of the rookery distribution differences in northern fur seals and Steller sea lions in the waters of the Russian far east

Abstract We investigated factors influencing differences in the rookery distribution patterns between northern fur seals and Steller sea lions in the waters of the Russian far east. The limited distribution of northern fur seal rookeries observed during 1991–2001 resulted from the need for shallow tide pools near the shore for pups to practice swimming. In addition, the large and concentrated populations of the seals required large flat areas and a high degree of natal site fidelity. In contrast, in the case of Steller sea lion rookeries observed along the Kuril islands in 2001, the pups were able to swim under maternal care, and their populations were smaller and had a lower degree of natal site fidelity. So, from our observations, their rookeries, unlike those of northern fur seals, are therefore widely distributed across diverse topographical conditions in the waters of Russian far east.