INTRODUCTION

There are many reasons to capture study animals. They include marking or radio-collaring (Chapter 10), taking morphological measurements (Chapter 9), or biological samples (Chapters 1 and 8), and estimating age and condition. For small nocturnal primates, capture is essential to radio-tag animals for direct observation, the most effective method of determining the spatial distribution and social interactions of individuals and estimating population densities (Chapter 6; Sterling et al., 2000). Historically, studies in which wild, larger-bodied, primates are habituated for long-term observation have rarely included capture, perhaps because researchers have been understandably wary of its effects on subsequent behaviour and habituation (Chapters 2 and 11). However, a survey of more than 120 studies that combined observation with capture, and which involved about 65 primate species, showed that a careful capture–release programme using trapping will not cause a previously habituated population to change its behaviour towards human observers, and will not be associated with excess mortality or serious injury (Jolly & Phillips-Conroy, 1993 and unpublished data). Changes in ranging habits will be temporary at worst, and basic social organization and structure will not be affected. The survey also provided a comparison between capture methods. Trapping has been used most often to catch diurnal-terrestrial and nocturnal-arboreal species. Diurnal-arboreal primates (apart from callitrichines) have generally been captured by darting (Chapter 8), a bias that seems unjustified.

INTRODUCTION

There are many reasons to capture your study animals, including marking or radio-collaring individuals (Chapter 10), taking morphological measurements (Chapter 9) and biological sampling (Chapters 1 and 8). For small nocturnal primates, trapping may be the only way to gather data for density estimates (Chapter 6). Furthermore, it is essential for the determination of spatial distribution and social interactions of individuals, as the most effective method uses direct observation of radio-tagged animals (Sterling et al., 2000). Historically, studies in which wild, larger-bodied non-human primates (hereafter called primates in this chapter) are habituated for long-term observation have rarely included capture, perhaps because researchers have been understandably wary of its effects on subsequent behaviour and habituation. However, our survey (Jolly & Phillips-Conroy, 1993; C. J. Jolly and J. E. Phillips-Conroy, unpublished data) of more than 120 studies that combined observation with capture, and which involved about 65 primate species, showed that a careful capture–release programme using trapping will not cause a previously habituated population to change its behaviour towards human observers, and will not be associated with excess mortality or serious injury. Changes in ranging habits caused by baiting and trapping will be temporary at worst, and basic social organisation and structure will not be affected. The survey also showed that trapping has been used most often to catch diurnal–terrestrial and nocturnal–arboreal species. Diurnal–arboreal primates (apart from callitrichines) have generally been captured by darting (Chapter 8), a bias that seems unjustified.

Introduction

Individual age is an important parameter in studies of primate sociobiology, ecology, and population genetics. As well as being a major determinant of behavior (Dunbar, 1988), it is critical for the construction of life tables, as a scale against which to plot measures of growth and maturation, and (if translated into date of birth) to provide a timescale for microevolution. Yet only a few exceptionally long and continuous primate field studies document age directly, from individual birth-to-death life histories of substantial numbers of animals. In other cases, individual age must be estimated from unreliable indicators such as external appearance or deportment. However, dental eruption, and subsequent wear of the occlusal surface, displays progressive change extending over most of an animal's lifetime. Where animals can be caught or restrained, dental evidence provides a basis for estimating the age of those whose life history is otherwise undocumented, as long as the timetable of eruption and wear can be reliably calibrated by reference to animals of known birth date. Elsewhere (Phillips-Conroy and Jolly, 1988), we have documented the sequence and timing of dental eruption in wild yellow baboons (Papio hamadryas cynocephalus) and hamadryas baboons (P. h. hamadryas), using animals of known natal age. Here, we develop a method of using the exposure of dentine on the occlusal surface of the molar teeth to estimate age, and apply it to adult individuals. By incorporating data from two populations, we are also able to explore interpopulation differences in dental wear rate.