The Potential for Physiological Performance Curves to Shape Environmental Effects on Social Behavior.

Shaun S. Killen,Christos C. Ioannou,Amelia Munson,Lucy Cotgrove,Daphne Cortese,Jolle W. Jolles

doi:10.3389/fphys.2021.754719

Abstract

As individual animals are exposed to varying environmental conditions, phenotypic plasticity will occur in a vast array of physiological traits. For example, shifts in factors such as temperature and oxygen availability can affect the energy demand, cardiovascular system, and neuromuscular function of animals that in turn impact individual behavior. Here, we argue that nonlinear changes in the physiological traits and performance of animals across environmental gradients—known as physiological performance curves—may have wide-ranging effects on the behavior of individual social group members and the functioning of animal social groups as a whole. Previous work has demonstrated how variation between individuals can have profound implications for socially living animals, as well as how environmental conditions affect social behavior. However, the importance of variation between individuals in how they respond to changing environmental conditions has so far been largely overlooked in the context of animal social behavior. First, we consider the broad effects that individual variation in performance curves may have on the behavior of socially living animals, including: (1) changes in the rank order of performance capacity among group mates across environments; (2) environment-dependent changes in the amount of among- and within-individual variation, and (3) differences among group members in terms of the environmental optima, the critical environmental limits, and the peak capacity and breadth of performance. We then consider the ecological implications of these effects for a range of socially mediated phenomena, including within-group conflict, within- and among group assortment, collective movement, social foraging, predator-prey interactions and disease and parasite transfer. We end by outlining the type of empirical work required to test the implications for physiological performance curves in social behavior.

Highlights

Within species there exists considerable among-individual variation in numerous physiological traits associated with energy demand (Burton et al, 2011; Metcalfe et al, 2016), cardiorespiratory systems (Walsberg et al, 1986; Brijs et al, 2019), and neuromuscular function and movement (Wilson et al, 2004; Marras et al, 2010)
It is becoming increasingly clear that: (1) animal social behavior is linked with the physiological performance capacity of individuals; and (2) physiological performance is strongly influenced by environmental factors
The measurement of performance curves has been a central feature of the study of comparative physiology and ecophysiology during the last several decades, but in virtually all cases has only been applied to individual animals and devoid of any social context

Summary

Introduction

Within species there exists considerable among-individual variation in numerous physiological traits associated with energy demand (Burton et al, 2011; Metcalfe et al, 2016), cardiorespiratory systems (Walsberg et al, 1986; Brijs et al, 2019), and neuromuscular function and movement (Wilson et al, 2004; Marras et al, 2010). Social grouping ranges from pairs of animals to large scale communities and enormous aggregations consisting of millions of individuals Variation in this tendency to group, both at the individual and species level, can be explained by the balance between the benefits of reducing predation risk, improving foraging and saving energy during locomotion, vs the costs of competition within groups over food and the opportunity to breed, and a greater exposure to socially-transmitted diseases. These benefits and costs can be shifted, by individuals’ behavior within groups, with effects on social interactions and group functioning (Jolles et al, 2017; del Mar Delgado et al, 2018). There is evidence of direct links between metabolic demand and sociability, with individuals with a higher metabolic rate being perhaps less social and less likely to associate with conspecifics (Killen et al, 2016b; Cooper et al, 2018; but see Killen et al, 2021)

Objectives

Conclusion