Introduction

Much evidence has now accumulated to demonstrate that individuals respond differentially to conspecifics according to their genetic relatedness (e.g. Hepper, 1986a; Fletcher & Michener, 1987; see also this book). Furthermore, this differential responding is not confined to one particular behaviour but is found in a diverse variety of situations and behaviours (see this book). This strongly suggests that individuals have some means which enable them to identify genetic relatedness. It is the aim of this chapter to explore how individuals recognize their kin. Previously (e.g. Hepper, 1986a; Porter, 1987; Waldman, 1988) this ability has been considered under the general rubric of the ‘mechanisms’ of kin recognition. This chapter will discuss factors which contribute to the individual recognizing its kin and will, by addressing these factors, enable the underlying basis of kin recognition to be elucidated. Although the chapter will concentrate on mammalian kin recognition it is hoped that the considerations presented will be applicable to other animal groups. I shall first discuss present approaches to mechanisms of kin recognition.

In Hamilton's seminal papers of 1964 (a,b), as well as demonstrating the fitness benefits to an individual of responding differentially to kin and nonkin, a number of ways were proposed by which individuals would be able to discriminate between kin and non-kin in social situations. From this discussion (Hamilton, 1964b) and that of others (e.g. Alexander, 1979; Bekoff, 1981; Hölldobler & Michener, 1980) four basic ‘mechanisms’ have been proposed to explain how individuals recognize their kin (Holmes & Sherman, 1983). These have become firmly rooted in the literature and I shall outline each briefly.