Introduction

The fundamental issues that confront students of cooperative breeding are delayed dispersal or philopatry, helping behavior, and delayed breeding. These are central questions, regardless of the taxonomic group under study or the level of analysis (mechanistic, developmental, functional, or evolutionary) that guides the formation of questions about cooperative breeding (Brown 1987; Emlen 1991; Mumme this volume). The first set of questions concern philopatry and delayed dispersal. What are the ecological factors that promote retention of individuals, often offspring of the breeding adults, in the social group? Does the pattern of intragroup social interactions differ in species that exhibit delayed dispersal from those in which offspring disperse at sexual maturation (Chepko-Sade & Halpin 1987)? What are the relative roles of the benefits for delayed dispersers that may accrue from philopatry with respect to potential constraints on dispersal (Koenig et al. 1992; Mumme this volume)?

The second question concerns the expression of helping or alloparental behavior. The primary issues here concern, on a proximate level, the underlying physiological (e.g., Carter & Roberts this volume), motivational (Pryce 1992; Pryce, Döbeli, & Martin 1993), and behavioral (Tardif, Harrison, & Simek 1993; Tardif, this volume) regulation of care-giving behavior in alloparents. Are these mechanisms controlling alloparental care similar to those that control maternal and paternal behavior, or have the control systems been modified and specially adapted for alloparental care (e.g., Jamieson 1989)?