Constraints and flexibility in mammalian social behaviour: introduction and synthesis

Abstract

This paper introduces a Theme Issue presenting the latest developments in research on the interplay between flexibility and constraint in social behaviour, using comparative datasets, long-term field studies and experimental data from both field and laboratory studies of mammals. We first explain our focus on mammals and outline the main components of their social systems, focusing on variation within- and among-species in numerous aspects of social organization, mating system and social structure. We then review the current state of primarily ultimate explanations of this diversity in social behaviour. We approach the question of how and why the balance between behavioural flexibility and continuity is achieved by discussing the genetic, developmental, ecological and social constraints on hypothetically unlimited behavioural flexibility. We introduce the other contributions to this Theme Issue against this background and conclude that constraints are often crucial to the evolution and expression of behavioural flexibility. In exploring these issues, the enduring relevance of Tinbergen's seminal paper 'On aims and methods in ethology', with its advocacy of an integrative, four-pronged approach to studying behaviour becomes apparent: an exceptionally fitting tribute on the 50th anniversary of its publication.

Figure 1.

Determinants of behavioural flexibility. Determinants and levels of behavioural flexibility are depicted for individuals (below solid line) and social units (above solid line). Beginning with fertilization (lower left corner), several factors shape individual behaviour patterns, both before (light grey box) and after birth (dark grey box). (a) Over their lifetime, individuals may exhibit social flexibility (or ‘plasticity’) in particular behaviour patterns. (b) Different individuals of the same species may exhibit interindividual variation in behaviour (‘personality’). (c) Individuals are socially organized into social units (neighbourhoods, pairs or groups) that may exhibit variation in social organization over time or (d) within populations (d), either as a result of chance effects or changes in environmental conditions. Behavioural variation at this level is mostly due to transmission of socially learned behaviour patterns. (e) Different populations of the same species may vary in social organization, mating system or social structure, presumably most often in response to ecological gradients. (f) Species differences in social systems appear to have a strong genetic component, including phylogenetic signals.