Colobines display an array of different types of social organization. In some Asian colobines (most prominently the snub-nosed monkeys, Rhinopithecus spp.) and one subspecies of African colobine, social organization is multilevel, i.e. social units are characterized by a complete absence of exclusive territories, occupy wholly shared ranges and are nested within a larger, bounded social matrix. This chapter reviews and discusses the composition and social dynamics of colobine multilevel societies as well as the causes and consequences of living in such a complex social setting.

Fossil colobines are found in Africa, Asia, and Europe and as far back as over 12 million years ago. They are known from paleontological sites that extend well beyond their current range to northern Europe and Asia. In the late Miocene (10 – 5 Ma) they are quite rare but show a pattern of steadily increasing diversity. By Pliocene times they are considerably more diverse than today in terms of number of genera. They also span a greater range of body sizes extending from some similar to extant colobines up to at least three lineages that probably exceeded 40 Kg. Dental morphology, microwear analysis, and stable isotopes of carbon and oxygen further suggest that they had a range of diets, many likely different than extant colobines. Postcranial morphology suggests a wider range of locomotor modes as well. Finally, many seemed to have occupied more open, seasonal, and varied habitats than extant forms.

The odd-nosed monkeys represent a monophyletic group of phenotypically unique primates. They include five species of snub-nosed monkeys (Rhinopithecus), three species of doucs (Pygathrix) as well as simakobu (Simias concolor) and the proboscis monkey (Nasalis larvatus). These species are ecologically diverse and inhabit a gradient of environments in China and southeast Asia, from wet equatorial forests to alpine forests. Odd-nosed monkeys tend to be shy and difficult to habituate, and often range over relatively large areas. Many are also renowned for inhabiting remote areas with rugged terrain and inclement climatic conditions. It is thus not surprising that, until fairly recently, they were among the least studied and most enigmatic extant diurnal primates. However, since the beginning of the new millennium, an expanse of new and exciting research has been conducted on these colobines. In this chapter, we provide an overview of the current knowledge of the ecology and behaviour of odd-nosed monkeys and analyse some of their key behavioural traits and ecological adaptations in light of what is known about other colobines and primates as a whole.