costs, predation pressures, and the production of precocial
young may all influence the behavior of these animals, the
specific blend of selective pressures and adaptive conse-
quences that shape social structure seems likely to vary
among species. Acknowledging the multivariate nature of
interactions between environment and social structure does
not preclude the search for general correlations between en-
vironmental conditions and sociality, although it may ren-
der the identification of those relationships more challeng-
ing. Thus while we suspect that many of the ecological and
other potential selective forces identified here are impor-
tant, we expect that their contributions to social structure
vary not only between octodontids and ctenomyids but also
within each family.
To exploit fully the comparative opportunities afforded
by these animals, we suggest that future studies of these an-
imals should address the following objectives:
1.Characterization of social systems. At present, the
behavior of most species in these families remains un-
known, and thus a primary goal of future research
should be to generate comparative information regard-
ing basic aspects of social structure such as the number
of adults of each sex that live together, the kin structure
of social units, and the social determinants of repro-
ductive success.2.Analyses of intraspecific variation in ecology and be-
havior. Comparative studies of conspecifics living in
different habitats provide a powerful means of assessing
the role of specific environmental variables in shaping
social behavior. Because such comparisons effectively
control for differences in evolutionary history that may
confound cross-taxon analyses, identifying causal re-
lationships between environmental conditions and
behavior is facilitated.
3.Experimental manipulation of causal factors. Con-
trolled manipulation of environmental variables is a
compelling approach to testing proposed causal rela-
tionships between ecology, life history, and variation
in social behavior. Experiments conducted in field set-
tings are often challenging, but even relatively simple
manipulations may yield important information regard-
ing the effects of specific factors on social structure.Although much work is required to generate a compre-
hensive picture of the social biology of octodontid and cte-
nomyid rodents, the growing number of studies of these
animals suggests that such data will be forthcoming. As our
knowledge of these families increases, we expect that octo-
dontids and ctenomyids will come to play an increasingly
prominent role in our understanding of rodent societies.Social Structure in Octodontid and Ctenomyid Rodents 415