INTRODUCTION

Field biologists adopted the term habituation from physiology, as the relatively persistent waning of a response as a result of repeated stimulation that is not followed by any kind of reinforcement (Thorpe, 1963). Repeated neutral contacts between non-human primates (hereafter called primates in this chapter) and humans can lead to a reduction in fear, and ultimately to the ignoring of an observer. The techniques and processes involved have only rarely been described (e.g. Schaller, 1963; Kummer, 1995), as habituation has generally been viewed as a means to an end (Tutin & Fernandez, 1991). The few studies that have quantified primate behaviour in relation to habituators describe the process with African great apes (Grieser Johns, 1996; van Krunkelsven et al., 1999; Blom et al., 2001). As we become increasingly aware of the potential effects of observer presence on primate behaviour, and especially the potential risks of close proximity with humans, it behoves us to measure as much as possible about the habituation process.

Many behavioural responses are taxon specific, and these should be taken into account when one is trying to habituate human-naïve wild primates. Between us we have had experience with a wide range of wild primates, ranging in size from marmosets (Callithrix spp.) to gorillas (Gorilla spp.), from South America, Africa, Madagascar and Asia, which, together with discussions with colleagues, we have used to make this chapter as broadly applicable as possible.