Abstract: The structure of primate communities living in a number of undisturbed areas is described and compared. Species richness is highest in tropical rain forests of Africa and South America, where up to 14 different species can share the same habitat. The number of sympatric primates in woodlands and savannas is always much lower. Some striking differences in community structure may be observed between communities living in apparently similar habitats. Three major factors may be held responsible for such discrepancies: history and paleoecology, present spatial heterogeneity of the vegetation, and competition with other taxonomic groups. The role of primates in the functioning of forest ecosystems is discussed. Though their trophic impact may be important, the role they play in seed dispersal appears to be more significant; they contribute greatly to homeostasis, as well as to regeneration, of the rain forests. A number of ecological traits are particularly developed among primates and may have contributed to the rapid evolutionary success of the order. Their predominantly vegetarian diet allows them to build up higher population densities than sympatric carnivorous mammals;their arborealism permits them to make use of all edible plant material available in a tridimensional environment; the opportunistic tendencies of some cebids, cercopithecids, and pongids enable them to take advantage of a variety of habitats and situations; and finally, an extended socialization period and a long life-span, allowing them to develop social traditions, give to many of them a further possibility to adapt quickly to novel situations.

Abstract: Observations of play behavior were made on a troop of Japanese monkeys for five months. The troop consisted of 125 animals during the study period. Only 104 animals were observed playing with the troop members while the other 21 animals were never observed playing with other individuals. Two-member play was the most frequent. On the average, a monkey played with 20.7 individuals. A total of 6,068 play bouts were observed. The frequency of play appeared to be affected by age, sex, and degree of relatedness. One-year-old infant males played most with other members and the frequency of play decreased with age. Between monkeys whose disparity of age was less than two years, 5,763 bouts (95.0% of the total) were observed. Moreover, among sameaged monkeys who comprised 10.6% of the possible pair combinations, 2,739 play bouts (45.1%) were observed. Juvenile males played with same-sexed peers more than with opposite-sexed peers, whereas older juvenile females appeared to play with infants of both sexes. Individuals who were related and similarly-ranked tended to play together. There was no apparent preference for animals to play with the offspring of the highest-ranking female. Dominance rank of infnats and juveniles was primarily affected by rank of their mothers and to a lesser extent by play partners. Dominance rank of older juvenile males is more likely to be affected by play partners than females. It may be a critical time for males when they leave their natal troop and join a new troop. The timing of troop shifting by males seemed to be affected by the presence or absence of play-mates. For male Japanese monkeys, play is very important in developing social bonds. Play may act to perpetuate social bonds, enhance the chance of survival, and may contribute to their future reproductive success.

Abstract: Abstract and Summary: Since the adaptive significance of social organization is emphasized diversely in both anti-predator behaviour and food searching of birds, measures and comparisons of observational learning capacity of various species are needed. Four different experimental situations were built up for juvenile and adult individuals of tits (Parus major, P. caeruleus, P. palustris) and thrushes (Turdus merula, T. philo-melos). The birds learn more easily from conspecifics and learn easily when they already know a previous problem solving situation. The capacity of observational learning of the adult great tits surpasses that of adult blue tits and marsh tits, and that of the adult blackbirds exceeds that of the adult songthrushes. The higher performance of the great tit and blackbird can be related to their greater hemispheric index. The differences in the learning capacity of the naive individuals of the three tit species and that of the two thrush species were not significant. It is suggested, that the higher observational learning of the great tit and blackbird is evolved through maturational processes and can be reflected by their greater adaptability. Zusammenfassung: Lernen durch Nachahmung wurde in vier verschiedenen Situationen mit jungen und alten Individuen von Meisen- (Parus major, P. caeruleus, P. palustris) und Drosselarten (Turdus merula, T. philomelos) untersucht. Die Vögel lernten besser von Artgenossen und lernten leicht, wenn sie vorher bereits eine Problemlösungssituation kannten. Die Lernfähigkeit (durch Nachahmung) alter Kohlmeisen übertraf die alter Blau- und Sumpfmeisen; die Lernfähigkeit alter Amseln übertraf die alter Singdrosseln. Die höhere Leistung der Kohlmeisen und Amseln hängt mit ihrem höheren Hemisphären-Index zusammen. Naive Individuen der Meisen- und Drosselarten zeigten keine signifikanten Unterschiede in ihrer Lernfähigkeit. Es ist anzunehmen, daß die höhere Lernfähigkeit der Kohlmeise und der Amsel im Laufe der Entwicklung durch Reifungsprozesse zustande kommt und sich in ihrer höheren Anpassungsfähig-keit widerspiegelt.

Abstract: Innovative behaviour achieved through exploration, learning and insight heavily depends on certain motivational, social and ecological conditions of short duration. We propose that more attention should be given to what these conditions are and where they are realized in natural groups of non-human primates. Only to the extent that such favourable conditions were frequently realized in a social structure or an extraspecific environment could selective pressures act on innovative abilities. There is hope that research into field conditions of innovative behaviour will help to identify its selectors in evolution.