T
he Rodentiais the largest order of mammals,
consisting of more than 2,000 species and compris-
ing 44% of all mammals. Rodents come in a variety
of body shapes, from cylindrical to spherical, and sizes,
from less than 10 g to more than 66 kg. The characteristic
that unites this order — and is its most conspicuous trait —
is a single pair of razor-sharp incisors, which are used to
gnaw food, excavate tunnels, and defend themselves. The
name “rodent” derives from the Latin word rodere,which
means “to gnaw.”
No matter where you live, a rodent is probably not far
away. Rodents inhabit all continents except Antarctica, and
they occur in terrestrial, subterranean, arboreal, and aquatic
habitats — from the high arctic tundra to equatorial rain for-
ests, temperate bogs and swamps to hot, arid deserts, and
rocky mountaintops to sandy canyon bottoms. Many spe-
cies live in close association with humans. With such var-
ied characteristics and expansive ecology, rodents provide a
range of attributes that have captivated scientists and an-
noyed laypersons for hundreds of years.
The diversity of rodents, and the ease with which many
species can be maintained in captivity, has led to their
choice as model systems for observational and experimen-
tal studies in genetics, ecology, demography, physiology,
and psychology. The social and reproductive behaviors of
rodents also are diverse and intriguing. Although most ro-
dents are nocturnal, a surprising amount of research has
been conducted on rodent social biology. As a result, large
databases are available, and these can be used to test hy-
potheses about the ecological and evolutionary forces that
mold mammalian social and reproductive behaviors. Many
aspects of behavioral ecology are similar across species
(e.g., the effects of resource distributions on mating systems
[Slobodchikoff 1984; Ostfeld 1990]; the role of ecological
factors in favoring group-living [Hoogland 1995; Eben-
sperger and Cofré 2001]; and the role of kinship in struc-
turing social interactions [Sherman 1981a; Lacey and Wiec-
zorek 2003]). Unifying theories developed from other taxa,
such as primates, ungulates, or canids, can be experimen-
tally tested in the field and laboratory with rodents. These
options are not so readily available for the larger, wider-
ranging taxa. Thus rodents are not only models for testing
hypotheses developed from rodents, but they have become
models for other taxa as well. The relevant information,
however, is widely scattered and sometimes conflicting.
Hence this volume.
Our goals were to synthesize and integrate the current
state of knowledge about the social behavior of rodents, to
provide ecological and evolutionary contexts for under-
standing rodent societies, and to highlight emerging con-
servation and management issues to preserve these socie-
ties. Thus we attempted to emulate Primate Societies(1987)
and Cetacean Societies(2000), the two outstanding preced-
ing volumes in this series published by the University of
Chicago Press.
In selecting topics and contributors for the present vol-
ume, we first chose areas of behavioral biology and model
species that we considered essential for understanding the
adaptive significance of rodent social behavior generally.
Then we invited contributions from researchers who have
demonstrated their preeminence in illuminating these areas
and in studying the focal taxa. We urged authors to use the