Yasuko Tashiro

Fruit availability and habitat use by chimpanzees in the Kalinzu Forest, Uganda : Examination of fallback foods

We studied seasonal change in habitat use by chimpanzees in the Kalinzu Forest, Uganda. The forest comprises various types of vegetation. For each vegetation type, we compared number of chimpanzees (per km2) that used the vegetation with fruit availability in different census periods. We estimated the number of chimpanzees by nest count and fruit availability via density of fallen fruit. The mixed mature forest contained a large amount of fruit during the high-fruiting season, but it decreased rapidly in the low-fruiting season. The number of chimpanzees also decreased in mixed mature forest in approximate proportion with fruit availability. In the Parinari-dominated mature and secondary forests, both fruit availability and number of chimpanzees were very low throughout the study. In the Musanga-dominated secondary forest, the number of chimpanzees increased toward the low-fruiting season, though the fruit availability decreased slightly. A multiple regression analysis showed that various fruits had significant effects on the number of chimpanzees during the high-fruiting season, while only Musangaleo-errerae had a significant effect during the low-fruiting season. The results suggest that the fruit of Musanga leo-errerae functions as a fallback food, and a combination of different vegetation types supports the chimpanzees in the Kalinzu Forest.

What Factors Affect the Size of Chimpanzee Parties in the Kalinzu Forest, Uganda? Examination of Fruit Abundance and Number of Estrous Females

We examined factors affecting the size of chimpanzee parties in the Kalinzu Forest, Uganda. We found that the number of individuals in a party increased with observation time. Therefore, we employed two methods to reduce this bias: (1) we evaluated party size via the mean number of individuals observed in each 1-h period during the observation of a party (1-h party size), and (2) we used the number of all individuals observed in a party (1-day party size) and performed an analysis of covariance, with observation time of the party as the covariant. We examined factors that might affect party size: fruit abundance, fruit distribution, and number of estrous females. There was no relationship between party size and fruit abundance or distribution. Conversely, the number of males has a significant positive correlation with the number of estrous females, though there is no correlation with the number of anestrous females. These results suggest that males tended to join parties with more females in estrous, irrespective of differences in fruit availability.

Habitat Use and Ranging of Wild Bonobos (Pan paniscus) at Wamba

The relationship between vegetation and ranging patterns of wild bonobos at Wamba, Democratic Republic of the Congo, was examined. Via Landsat data, we distinguished three types of vegetation—dry forest, swamp forest, and disturbed forest—at Wamba. The home ranges of the study groups changed considerably from year to year, due mainly to intergroup relationships. The population density of each group varied between 1.4 and 2.5 individuals per km2and was lowest during a period of population increase. Home ranges consisted mainly of dry forest. The bonobos used dry forest more frequently than the other forest types, though they also used swamp and disturbed forest almost every day. The latter types of forest seemed to be important resources for the bonobos, owing to the abundant herbaceous plants that are rich in protein and constantly available. The bonobos tended to use dry forest more frequently in the rainy season than in the relatively dry season, probably because the favored fruits in the dry forest were mostly available in the rainy season. There was no seasonal difference in the size of the daily ranging area.

Ant dipping and meat eating by wild chimpanzees in the kalinzu forest, uganda

New evidence of ant dipping and meat eating by chimpanzees was recorded in the Kalinzu Forest, Uganda. We found stems and branches at the nests of driver ants,Dorylus molestus, just after chimpanzees had left the spot. Fecal samples also revealed that chimpanzees sometimes ate driver ants. The configuration of stems and branches and the condition of holes at the driver ants nests suggested that chimpanzees used them as wands to dip for ants. The frequency of ant dipping and length of wands may be more related to culturel rather than ecological factors. Although hunting was not seen, we found chim-panzees eating a blue monkey and a redtail monkey. In both cases, they ate meat and leaves alternatively, and shared meat with each other.

Seasonal Changes in Fruit Production and Party Size of Bonobos at Wamba

Because chimpanzees (Pan troglodytes) have a unique fission-fusion social structure, many researchers have investigated the nature of foraging parties. They have reported that chimpanzees form foraging parties whose size and sex composition change flexibly, and that the sizes of parties may vary according to fluctuations in fruit abundance, the number of estrous females, or both (Wrangham 1977, Ghiglieri 1984, Isabyre-Basuta 1988, Stanford et al. 1994, Boesch 1996, Matsumoto-Oda et al. 1998, Newton-Fisher et al. 2000, Boesch and Boesch-Achermann 2000, Hashimoto et al. 2001). Researchers have also reported that females tend to join mixed-sex parties less frequently than males do, and that this likely occurs because ranging in large mixed-sex parties may not be beneficial to the feeding activities of females (Wrangham 1979, 2000, Janson and Goldsmith 1995, Williams et al. 2002, Reynolds 2005). The closest relative of chimpanzees, bonobos (P. paniscus), have a similar fissionfusion social structure. However, the size and composition of the parties are different from those of chimpanzees. Previous studies of bonobos at Wamba and Lomako in the Democratic Republic of the Congo showed that bonobos form larger and more stable parties (Kuroda 1979, Kano 1982, 1992, Furuichi 1987, White 1988), and that the size of parties may be influenced by fruit abundance to a lesser extent. This is probably because either the seasonal changes in fruit abundance are small or because some foods are available year-round (Kano 1982, Kano and Mulavwa 1984, White 1998, Malenky and Stiles 1991, Malenky and Wrangham 1994, Chapman et al. 1994). Furthermore, bonobo females tend to join mixed-sex parties

Long-Term Studies on Wild Bonobos at Wamba, Luo Scientific Reserve, D. R. Congo: Towards the Understanding of Female Life History in a Male-Philopatric Species

Long-term studies on wild bonobos began at Wamba, in the current Luo Scientific Reserve, in 1973. Except for several interruptions due to political instability and civil war, we have been conducting studies of identified individual bonobos over 35 years, providing valuable data on their population dynamics and life history. Although the number of groups and number of individuals in the northern section of the reserve decreased by half during the interruptions of the study, the number of members of the main study group has steadily increased since 2002 when we resumed the study. Our long-term data demonstrated the male-philopatric structure of the group. There is no confirmed case of emigration of males from the study group, and no case of immigration of males into the group. On the other hand, all females born into the study group disappeared by the age of 10 years, and females with estimated ages of 6–13 years immigrated into the study group. These ages of intergroup transfer are much earlier than those reported for chimpanzees. Exceptional cases of immigration of two adult males and two adult females with offspring occurred right after the war. It is likely that remnants of extinct groups joined the study group. Such integration of members of foreign groups highlights the peaceful nature of bonobo society. The study group is characterized by an extremely high tendency for female aggregation. Various factors, including high density of food patches, female initiative in ranging, prolonged estrus of females, and high social status of females, seem to be responsible for the high attendance ratio of females in mixed-sex parties. Our long-term observations therefore provided evidence for interesting behavioral contrasts with chimpanzees.

Vegetation of the Kalinzu Forest, Uganda: Ordination of Forest Types Using Principal Component

We analyzed the vegetation of the Kalinzu Forest, Uganda, using principal component analysis. We got two components by the analysis: one seemed to indicate the strength of environmental factors characteristic to the western part of the study area, and the other seemed to indicate the extent of disturbance by human exploitation. Using these components, we made a vegetation map that distinguished four types of vegetation: mixed mature forest, Parinari-dominated mature forest, Parinari-dominated secondary forest, and Musangadominated secondary forest. Preliminary analysis of the relationship between vegetation type and frequency of vocalization of chimpanzees suggested that these components would give important information for the study of habitat use by chimpanzees.

Monitoring the reproductive status of Japanese monkeys (Macaca fuscata) by measurement of the steroid hormones in fecal samples

The menstrual cycles as well as the pregnancy in female Japanese monkeys (Macaca fuscata) were monitored by measuring the fecal estradiol concentrations and relative amounts of fecal progesterone. Steroids from fecal samples were extracted by using a previously developed simplified two-step method and then measured by radioimmunoassay. We successfully demonstrated that the two-step method is effective and convenient for monitoring the reproductive status of Japanese monkeys.