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

Abstract

Intraspecific variation in social systems is widely recognized across many taxa, and specific models, including polygamy potential, resource defense, and resource dispersion, have been developed to explain the relationship between ecological variation and social organization. Although mammals from temperate North America and Eurasia have provided many insights into this relationship, rodents from the Neotropics and temperate South America have largely been ignored. In this review we focus on reports documenting intraspecific variation in spacing systems, group size, and mating systems of caviomorphs. This large group of New World hystricognath rodents occupies a diverse array of habitats; thus, members of the same species potentially exhibit different social systems in response to different ecological conditions. Spatial patterns vary in response to a diverse array of factors, including predation, food availability, population density, and soil characteristics. Changes in group size typically correlate with changes in resource availability, particularly food. Mating systems generally reflect the ability of males to control access to females, which may depend on population density or food distribution. In general, social organization in caviomorphs fits predictions of resource-based models; however, most studies have been purely observational, involving small numbers of animals over short time periods and reporting qualitative rather than quantitative levels of ecological correlates. In future studies the use of molecular techniques and controlled, experimental manipulations can increase our understanding of intraspecific variation in caviomorph social systems. This understudied group of rodents offers excellent opportunities to provide insights into the influence of ecological conditions on behavior such as social systems.

Intraspecific variation in social organization by genetic variation, developmental plasticity, social flexibility or entirely extrinsic factors

“…While the occurrence of intraspecific variation in social organization has received significant attention and acknowledgement recently, the focus has been on the associated ecological factors [13,16,17]. Additionally, we need to understand the different proximate and evolutionary mechanisms that arise from these ecological factors.…”

Use of space by the Neotropical caviomorph rodent Thrichomys apereoides (Rodentia: Echimyidae)

“…ZOOLOGIA 30 (1): 35-42, February, 2013 between the activities of females with the availability of food resources in this period. The availability of food resources has been considered as one of the most important factors that influence the pattern of use of space by mammals (ADLER 2011, ADRIAN & SACHSER 2011, MAHER & BURGER 2011. Depending on the spatial and temporal distribution of resources (ADLER 2011), in order to maximize their fitness, female rodents tend to be territorial when food resources are scattered with lower renewal rates, while the males are distributed according to the space used by the females (OSTFELD 1985).…”

“…Depending on the spatial and temporal distribution of resources (ADLER 2011), in order to maximize their fitness, female rodents tend to be territorial when food resources are scattered with lower renewal rates, while the males are distributed according to the space used by the females (OSTFELD 1985). Consequently, the spacing pattern of individuals has often been investigated in order to determinate the mating system of species (EMLEN & ORING 1977, OSTFELD 1985, GAULIN & FITZGERALD 1988, MAHER & BURGER 2011. A pattern that has been found for some species of rodents based on space use is the polygyny (GAULIN & FITZGERALD 1988, OSTFELD 1990).…”

“…A number of life history factors have been used to explain this variation among individuals including age, sex, season, breeding season, and population density (MAGNUSSON et al 1995, KELT & VAN VUREN 2001, ENDRIES & ADLER 2005. It has also been shown that the spacing pattern is associated with the social mating system used (ADLER 2011, MAHER & BURGER 2011, with the dispersion in the environment of individuals being strongly influenced by the way they behave in accordance to their needs and their role in their particular mating system (CLUTTON-BROCK & HARVEY 1978, GITTLEMAN & THOMPSON 1988.…”

“…It has been shown that different populations of the same species, or even the same population at different times, may vary in their social systems and spacing pattern due to ecological factors (see MAHER & BURGER 2011). Among caviomorph rodents, for example, distribution and availability of food resources, climatic conditions, and predation risk have been correlated with, and used to explain, intraspecific variation in the characteristics of home range and use of space (ADLER 1998, 2011, ADRIAN & SACHSER 2011, MAHER & BURGER 2011.…”