Introduction

The mechanisms of kin recognition have received much attention in recent years (e.g. reviews by Holmes & Sherman, 1983; Sherman & Holmes, 1985; Hepper 1986a; Waldman, 1987). However, most treatments of this topic have concentrated almost exclusively on the mechanisms by which animals are able to ‘recognize’ or classify conspecifics as either kin or nonkin. The signals or cues produced by animals and utilized by conspecifics to identify kin have, on the other hand, received only scant attention (but see Beecher, 1982; Hepper, 1986a; Waldman, 1987). Beecher (1982) stresses that ‘identification’ (the production of a signal that indicates the identity of the sender) is an important component of kin recognition which may have a significant impact on the fitness of the recipients of altruistic or nepotistic acts. Thus, discussions that focus only on the ‘recognition’ component of kin recognition address only one half of the question. An understanding of the ‘identification’ component and of the cues used for identification is essential if we are to develop a complete understanding of the mechanisms of kin recognition.

Halpin & Hoffman (1987) suggest that, in studying the cues used in kin recognition, two related but separate sets of questions need to be addressed: (1) whether the cues used for recognition are phenotypic labels shared by all genetic relatives (e.g. a family-specific label), or whether such cues are individually distinctive and, as such, provide no direct information on the genetic relatedness of conspecifics; and (2) whether the sensory cues used for kin recognition have a genetic basis or are environmentally acquired.