Abstract: When companion animal interact closely with people, the roles they play may be categorized in terms of three major functions. The projective function involves the extent to which pets may serve as a symbolic extension of the self. The sociability function involves the role of pets in facilitating human-to-human interaction. The surrogate function involves the extent to which interaction with pets may supplement human-to-human interaction, or serve as a substitute for it. A person publicly identified with a companion animal makes a symbolic statement of their personality and self-image. Whether or not this process is intentional, the presence of a pet and the way it is treated become factors which are taken into account in the assessment of the social self. Pets facilitate interaction by being social lubricants. They provide a neutral subject of conversation, and perform a variety of functions as social catalysts. Since interaction with companion animals can approximate human companionship, the presence of pets may serve to supplement the benefits usually derived from the roles of friend, parent, spouse, or child. Alternatively, pets may serve as surrogate antagonists. In the extreme, interaction with companion animals may not only supplement human companionship, but may actually replace it. These three major functions are discussed with examples. Implications are noted for future research on companion animals.

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.