direct descendents, increasing sociality may involve the re-
laxation of restrictions on interactions among group mem-
bers, resulting in a more inclusive and egalitarian society.
This is not always the case, as many eusocial species form
highly regimented societies characterized by extreme repro-
ductive skew (Sherman et al. 1995). For ground squirrels,
however, both Michener (1983a) and Rayor and Armitage
(1991) suggested that discrimination among individuals
from neighboring litters waned with more complex social-
ity, consistent with the eventual appearance of more inclu-
sive social constructs. Barash (1973) also noted that with
more complex sociality, as seen in Olympic marmots, all
parts of the colony become equally available to all colony
members. Measures of inclusivity, both in terms of space
use and behavioral interactions, may thus prove as useful in
cross-taxa comparisons examining the adaptive basis of so-
ciality as measures of reproductive skew.
The acknowledgment that benefits of sociality extend be-
yond those encompassed under kin selection does not deny
the fundamental importance of kin selection to ground
squirrel sociality. The formation of kin clusters, regardless
of the primary selective force producing such clustering, en-
sures that kin overlap in space and time. Thus cooperation
among individuals will be subject to kin selection. Perhaps
the most important question, not only for our understand-
ing of ground squirrel sociality, but for the survival of our
own species, is the extent to which the genetic selfishness
underlying social evolution can ultimately be directed to-
ward the common good.SummaryComparative analyses reveal that multiple ecological fac-
tors, including the reduced length of the growing season at
higher elevations, nutritionally poor environments that pro-
mote delayed dispersal, a harsh winter climate favoring
group hibernation, the clumped distribution of burrows,
and antipredator benefits of group living contribute to the
evolution and maintenance of ground squirrel sociality
(fig. 29.4).
Female philopatry, resulting in spatial and temporal
overlap of kin, is common among ground squirrels, and has
promoted the appearance of nepotism. Kin selection may
thus contribute to ground squirrel sociality, though payoffs
accruing via indirect fitness are likely to be secondary to
those accruing via descendent kin, either through enhanced
survivorship or benefits associated with the inheritance of
territories. Uncertainty as to the function of social discrim-
ination, variation in the measures used to quantify social-
ity, and the absence of well-resolved molecular phylogenies
for some ground squirrel taxa limit our ability to under-
stand the evolution of ground squirrel sociality. We advo-
cate broader replication and the performance of manipula-354 Chapter Twenty-Nine
Figure 29.4 Flow diagram illustrating the proposed relationships between ecological factors, life history, and the evolution of
sociality in ground-dwelling squirrels.