D
eserts are difficult placesin which to live.
Animals must survive and reproduce under ex-
treme and unpredictable environmental conditions
that can include extended droughts lasting for months, even
years. Dramatic seasonal fluctuations in environmental con-
ditions are common, with temperatures extremely high in
the summer and below freezing in the winter. High temper-
atures and low humidity during the day are followed by cold
nights. Strong winds and unstable sandy soils hinder the
growth of vegetation (Cloudsley-Thompson 1975; Shenbrot
et al. 1999). Deserts are widely distributed on all continents
except Antarctica, and despite the high temperatures and
aridity, desert habitats can be quite diverse, leading to con-
siderable taxonomic diversity in desert-dwelling rodents
(Mares 1993; Degen 1996; Shenbrot et al. 1999).
To survive above ground in desert environments rodents
often must withstand periods of limited plant growth, re-
sulting in low primary production of vegetation, a sparse
and patchy distribution of food, and unpredictable food
abundance (Shenbrot et al. 1999; Randall et al., 2005).
Desert habitats usually have limited cover, and rodents are
preyed on by numerous predators (Randall et al. 2000; Ro-
govin et al. 2004). Finally, desert rodents are faced with the
physiological problem of maintaining a constant body tem-
perature while minimizing water loss in arid conditions.
Although the physiology and ecology of desert rodents
are well known (e.g., Genoways and Brown 1993; Shenbrot
et al. 1999), there is still much to be learned about behav-
ioral adaptations to the challenges of arid conditions. My
goal in this chapter is to examine how environmental condi-
tions in deserts limit or promote the social behavior of semi-
fossorial desert rodents that are unable to escape extreme
temperatures and aridity by living totally underground. For
a better understanding, I sometimes contrast the behavior
of semifossorial rodents with the behavior of subterranean
rodents. See Nevo chap. 25, Lacey and Sherman chap. 21,
Lacey and Ebensperger chap. 34, and Faulkes and Ben-
nett chap. 36 this volume. I emphasize social adaptations
in what is fundamentally a solitary group of animals (Ran-
dall 1994). Although my analysis is somewhat constrained
by available information from studies under natural field
conditions, enough is known to develop these themes:
(1) physiological adaptations to water scarcity and high
temperatures place broad constraints on the behavior of
semifossorial desert rodents, (2) conditions of limited abun-
dance and patchy distribution of food inhibit the formation
of stable social groups and promote a solitary life style,
(3) desert rodents are often flexible and opportunistic in
their social adaptations to changing and unpredictable con-
ditions of arid environments, (4) when social groups do
emerge, dispersal is delayed, leading to the retention of
young in the natal area, social tolerance, and the sharing of
space by relatives, and (5) because of unpredictable condi-
tions of food abundance, social groups in deserts are often
unstable and density dependent. I will emphasize compar-
ative studies of semifossorial kangaroo rats (Dipodomys,
family Heteromyidae) and gerbils (family Muridae, subfam-
ily Gerbillinae), with pertinent research on other rodents to
provide insights into the evolution of social behavior in arid
environments.