Towards an integrative model of sociality in caviomorph rodents

Abstract

In the late 1990s and early 2000s it was recognized that behavioral ecologists needed to study the sociality of caviomorph rodents (New World hystricognaths) before generalizations about rodent sociality could be made. Researchers identified specific problems facing individuals interested in caviomorph sociality, including a lack of information on the proximate mechanisms of sociality, role of social environment in development, and geographical or intraspecific variation in social systems. Since then researchers have described the social systems of many previously understudied species, including some with broad geographical ranges. Researchers have done a good job of determining the role of social environments in development and identifying the costs and benefits of social living. However, relatively little is known about the proximate mechanisms of social behavior and fitness consequences, limiting progress toward the development of integrative (evolutionary-mechanistic) models for sociality. To develop integrative models behavioral ecologists studying caviomorph rodents must generate information on the fitness consequences of different types of social organization, brain mechanisms, and endocrine substrates of sociality. We review our current understanding and future directions for research in these conceptual areas. A greater understanding of disease ecology, particularly in species carrying Old World parasites, is needed before we can identify potential links between social phenotypes, mechanism, and fitness.

An evolutionary framework for studying mechanisms of social behavior

“…Fifty years after Tinbergen defined his proverbial 'four questions' [2], there is a tremendous opportunity for integrative studies on the ultimate and proximate mechanisms of complex behaviors such as sociality [7,[9][10][11]16,90]. Although the number of animal species considered to be accepted as biomedical model systems is decreasing [91], this trend is both paradoxical and misguided given that the very notion of a model system is undergoing rapid change and might soon be obsolete [92], at last liberating us to (again) use the species that are best suited for the problem in question (i.e., Krogh's Principle [93]).…”

Intraspecific variation in space use, group size, and mating systems of caviomorph rodents

“…However, because it is estimated that <10% of mammals are monogamous (Kleiman 1977), these studies should be viewed with caution. Whenever possible, molecular markers such as microsatellite primers (e.g., tucotucos [Lacey et al 1999], degus [Quan et al 2009], and corurus [ Spalacopus cyanus —Schroeder et al 2000]) should be used to determine maternity and paternity and measure direct and inclusive fitness, increasing our understanding of the links between environmental variation and social and mating systems in caviomorph rodents (Hayes et al 2011 [this issue]).…”

“…Next, we examine group size and mating systems, which result from particular spatial distributions of males and females (Brashares and Arcese 2002; Emlen and Oring 1977; Slobodchikoff 1984). Finally, we offer some recommendations for future work regarding the links between resources and intraspecific variation in social organization in this relatively understudied taxon (Ebensperger 1998; Hayes et al 2011 [this issue]; Tang-Martínez 2003). …”

Sociality, exotic ectoparasites, and fitness in the plural breeding rodent Octodon degus

“…remain unclear (Hoogland 1979). Given the potential for multiple modes of transmission (e.g., horizontally: adults-to-adults; vertically: mothers and nonkin nursing females to offspring), research into the fitness consequences of parasitism in communal breeders with extensive parental care may provide insight into the primary drivers of variation in fitness across social systems and taxa (Hayes et al 2011; Silk 2007). …”