Yakushima Macaques Research Articles

Seasonal variation in the feeding behavior and diet of Japanese macaques (Macaca fuscata yakui) in lowland forest of Yakushima.

The feeding behavior of the southern subspecies of Japanese macaque (Macaca fuscata yakui) was studied over a period of 18 months in warm temperate broad-leaved forest on the island of Yakushima, Japan. Focal animal data were collected for the eight adults in the troop. Over a full annual cycle, 35.0% of foraging on identified foods was on leaves and shoots, 30.2% on fleshy fruit, 13.2% on seeds, and 5.5% on flowers. Invertebrates and other animal matter accounted for 10.3% of foraging and fungi for 4.6%. There was marked seasonal variation in the use of different food categories, and seeds, leaves, fleshy fruit, and animal matter were each predominant at different times of year. There was also evidence of annual cyclicity in patterns of foraging on all major food types. The monkeys spent less time moving and ate a greater variety of foods when feeding on leaves than when feeding on fruit and seeds, or on insects. Time spent foraging was positively correlated with diversity of the diet, but there was no simple relationship between time spent foraging and the predominant food type. This suggests that a wide variety of foods takes longer to harvest and process, irrespective of the food type. The diet of the study troop was flexible and could not be assigned to a simple dietary category, such as frugivorous or folivorous. If these data are representative of the subspecies, the Yakushima macaque is much more of a dietary generalist than most primates for which there are adequate data.

Dietary selection by yakushima macaques (Macaca fuscata yakui): The influence of food availability and temperature

I examined dietary selection by Yakushima macaques (Macaca fuscata yakui)in relation to food availability and air temperature. Multiple regression analysis indicates that both food availability and temperature influenced the selection of foods. Feeding on young leaves, seeds, and flowers was affected more by availability, while feeding on fruits, mature leaves, and fallen seeds was affected more by temperature. Feeding on insects is strongly correlated with temperature,perhaps because availability of insects increased with temperature. These results suggest that temperature influences dietary selection of Yakushima macaques by changing the energy expenditure required for thermoregulation and through its influence on the accessibility to insects, which are an important protein source for the monkeys.

Foraging strategies of yakushima macaques(Macaca fuscata yakui)

I investigated the activity budget and diet of Yakushima macaques (Macaca fuscata yakui,)in warm temperate broad- leaved forest of Yakushima, Japan. Both time spent feeding and time spent moving varied considerably between half- months. However, total time spent in active behaviors— feeding time plus moving time— was stable. The composition of the diet also showed considerable variation between half- months. The macaques fed mainly on fruits, seeds,mature leaves, fallen seeds, flowers, and young leaves, each of which accounted for more than 30% of feeding time in at least 1 half- month. They also ate insects and fungi, but each of them comprised ≤ 25 and ≤ 8% of feeding time in any half- month, respectively. Time spent feeding on mature leaves, young leaves, flowers, or fallen seeds is positively correlated with total time feeding and is negatively correlated with time moving. In contrast, time feeding on fruits, seeds, insects or fungi is negatively correlated with time feeding and is positively correlated with time moving. Foraging on foods that have a low energy content, a high density, and a relatively even distribution— mature leaves— or that need much manipulation to be processed— flowers and fallen seeds— increased feeding time, while foraging on foods for which monkeys must search intensively in the forest— fruits, seeds, insects, and fungi— led to increased moving time. I examined foraging strategies of Yakushima macaques in terms of moving costs and the quality of food items. Regarding time feeding on fruits, which have more energy and may need less manipulation than other foods, as a benefit, and moving time as a cost, they seemed to employ a strategy that balanced the costs and benefits of foraging.

Rapid shifting of foraging pattern by Yakushima macaques (Macaca fuscata yakui) in response to heavy fruiting ofMyrica rubra

We describe short-term changes in foraging behavior by wild Yakushima macaques (Macaca fuscata yakui),which inhabit a warm-temperate broad—leaved forest on Yakushima Island (30°N, 131°E), Japan. Rapid changes of dietary composition, activity budget, and range use by the monkeys occurred from May to June, apparently associated with changes in the availability of the fruit of Myrica rubraBefore the fruit ripened, monkeys spent less time moving and more time feeding on many species of leaves, which accounted for 40% of feeding time. However, when M. rubrabegan to ripen, they fed intensively on the fruit, which accounted for three-fourths of feeding time,though the activity budget remained unaffected As fiuit of M. rubradecreased,the monkeys fed more on the fruit of other species and on insects, and spent more time moving at higher speeds. There marked shifts in foraging pattern occurred within only two months. In terms of moving cost and dietary quality,Yakushima macaques shifted their foraging pattern according to the availability of M. rubrafrom a “low-cost, low-yield” strategy to a “low-cost, high-yield” strategy, and then to a more costly strategy. The ability to make such rapid shifts in foraging pattern may allow the macaques to effectively use the highly variable food supply within their small range.

Foraging synchrony in a group of Yakushima macaques (Macaca fuscata yakui).

The synchrony of behaviour among individuals in a group of Yakushima macaques was evaluated in relation to group size and food resources. The degree of synchrony was greater when the group was small (5-8 individuals) than when it was large (15-19 individuals). Diet did not affect the degree of synchrony. However, the duration of the 'active phase', in which most members of the group synchronized feeding and moving, was shorter when they fed mostly on fruit and seeds (fruit- and seed-eating season) than when they fed mostly on leaves and fallen seeds (leaf- and fallen-seed-eating season). When the group was large, the monkeys ranged over a greater area and foraged in fewer trees during the fruit-and seed-eating season than during the leaf- and fallen-seed-eating season. However, this tendency was not so clear when the group was small. These results suggest that the extent to which the distribution of food resources determines patterns of foraging increases with group size and that monkeys in a larger group reduce levels of intragroup food competition in order to obtain sufficient food.

Absence of 'Youngest Ascendancy' in the Dominance Relations of Sisters in Wild Japanese Macaques (Macaca Fuscata Yakui)

AbstractDominance relations among females were studied in a small, well-habituated troop of Yakushima macaques (Macaca fuscata yakuz) in southernjapan. Data were collected using focal animal sampling over a 20-month period. Although the frequency of aggression was much lower than that reported for provisioned groups, and support in agonistic interactions was rare, a clear linear dominance hierarchy was apparent. In each of the four pairs of sisters in the troop the older was dominant to the younger. This is contrary to the pattern commonly reported for provisioned groups of Japanese and rhesus macaques, in which dominance among sexually mature sisters tends to be inversely correlated with age. For each pair of sisters in the study troop the mother was alive and healthy when the younger daughter became sexually active, but no cases were seen of a mother aiding one daughter against another. We therefore conclude a) that the absence of youngest ascendancy was due to a lack of support, rather than a lack of potential allies, and b) that both frequent agonistic support and youngest ascendancy are most likely to occur under conditions where concentrated food resources result in frequent and intense aggression.

Preliminary Survey of Relative Group Density of Macaca fuscata yakui in Relation to Logging History at Seven Sites in Yakushima, Japan

The forest habitat of the Yakushima macaque varies in quality as a result of logging, secondary growth and conifer plantations. A preliminary survey was made of macaque populations at 7 sites representing a range of habitat quality. All sites were located at between 300 and 800m asl, in the warm temperate broad-leaved forest zone in northwest Yakushima (30°N, 131°E), Japan. The extent of logging within a 1km2 plot at each site was assessed using image analysis of forestry maps. The proportion of the plot which had been logged within the previous 25 years ranged from 0 to about 68%, within 50 years from 0 to 79%, and within 75 years from 28 to 79%. Observations, vocalisations and droppings of macaques were recorded for a total of 284hr along census trails of between 2.2 and 3.5km. This included four ‘full’ days (7.5-8.5hr) for each site, which were used for the analyses. Macaques were found at all sites. The mean number of groups seen or heard ranged from 0.11 to 0.82/km/day, and was positively correlated (rs=0.64) with the proportion of mature forest at each site. There was no clear correlation between the mean detection rate of groups and the rate at which droppings were found. The latter may be a less accurate measure of relative group density in a short-term survey. Although Yakushima macaques do utilise areas within 25 years of heavy logging, more groups were found in areas where logging was less recent and/or less extensive. A long-term survey is now underway which will assess the details of this relationship, the influence of forestry plantations, and seasonal variation in use of different habitat types.

Frog- and lizard-eating behaviour of wild Japanese macaques in Yakushima, Japan

Frog- and lizard-eating and related behaviours were observed on eight occasions in two troops of wild Japanese macaques (Macaca fuscata yakui) in Yakushima, between March 1984 and April 1989. In each case, the first animal seen handling the prey was an adult. Juveniles showed interest in the prey, sniffed or mouthed it in three cases, and ate discarded parts of it in another. In the three cases where capture was observed, detection of the prey appeared to be fortuitous. Four monkeys ate leaves after eating meat. Those leaves identified were of species not commonly eaten. Though invertebrate-eating is common and widespread among Japanese macaques, the consumption of vertebrates is rare. The possibility that these behaviours represent a local tradition among the Yakushima macaques is discussed.