INTRODUCTION

The class Mammalia includes a diverse array of societies, from solitary species that rarely meet except for mating, to species so gregarious that they are rarely out of contact with their many group mates. Within this continuum, social monogamy is more likely to evolve in the less gregarious lineages, but remains a rare strategy across the class (Kleiman, 1977; van Schaik & Kappeler, chapter 4).

However, the mammalian class is dominated by solitary social systems that are rarely studied in detail (Eisenberg, 1981). Some have suggested that the secretive nature of many mammals has made them difficult to study, and that ‘solitary mammal’ has become a default termused to classify many of these elusive species. Leyhausen (1965) recognized this: ‘the main reasonwhy so many mammals are said to be solitary seems to be that they can only be shot one at a time’. Indeed, modern techniques such as radio telemetry, night vision, and molecular analyses have revealed surprising complexity and sociality among many species previously classified as solitary.

Among the Carnivora, telemetry work has found male associations in slender mongooses (Galerella sanguinea: Rood, 1989) and northern raccoons (Procyon lotor: Gehrt & Fritzell, 1998). An ambitious cadre of night-loving primatologists has revealed an amazing diversity of sociality among nocturnal primates (Kappeler, 1997; Bearder, 1999; Sterling et al., 2000).