Godfrey and Crowcraft 1960; Miller 1964). In general, ter-
ritories of same-sex individuals do not overlap, whereas
partial overlap occurs between male-female territories
(Howard and Childs 1959; Wilks 1963).
In accordance with the predictions of the optimal area
hypotheses, the territory sizes of subterranean mammals
vary with age, sex, body size, habitat, population density
(Nevo 1999), and diet. (For patterns of territoriality across
subterranean mammals see Nevo [1999, fig. 15.1n – p]). The
territories of subadults are considerably smaller than those
of adults, and females’ territories are smaller than those of
males. The size and shape of the territory are more constant
at high densities and more variable at low densities. Finally,
ranges of insectivorous species are significantly larger than
those of herbivorous subterranean mammals (Nevo 1999,
fig. 15.1o). Average territory size for Spalax microphthal-
musin Russia was 150 m^2 (Dukel’skaya 1935), for S. leu-
codonin Yugoslavia, 452 m^2 (range: 194 –1,000 m^2 ; Savic ́
1973). The larger territories of insectivores, when compared
with herbivores of the same size, strongly implicate re-
sources and energy in the selection for territory size (Mc-
Nab 2002; Brown and Orians 1970; Nevo 1999, fig. 15.1o).
Spacing patterns may shift from individual-territorial
to colonial as environmental conditions associated with
changes in food density occur (Brown and Orians 1970;
Reig 1970). Coloniality occurs, though infrequently, in sub-
terranean mammals — for example, in Ctenomys peruanus
(Pearson 1959; Genelly 1965), C. minutus, Spalacopus cy-
anus(Reig et al. 1970), Cryptomys hottentotus,and several
other species of AfricanCryptomys(Burda and Kawalika
1993) andHeterocephalus glaber(Hill et al. 1957; Sherman
et al. 1991; Jarvis et al. 1994; Jarvis and Sherman, 2002).
Heterocephalusalso evolved an adaptive hierarchic caste
structure (Jarvis 1981; Sherman et al. 1991; Jarvis et al.
1994; Jarvis and Sherman 2002; Nevo 1999, fig. 7.7b – f).
Some cases (e.g., Heterocephalus and Spalacopus) are as-
sociated with unfavorable climatic and /or resource condi-
tions, and their sociality was explained by the aridity-food
distribution hypothesis (see Burda [1989] and Foulkes and
Bennett, chap. 36 this volume).
Thus, territoriality and coloniality can be viewed as re-
sponses to spatiotemporal changes of exploitable resources.
Both patterns are consistent with a time-and-energy-budget
model (Brown and Orians 1970). The extreme case in spa-
lacids will be discussed subsequently.
Territory, Size, and Population Density
in the Spalax ehrenbergiSuperspecies
The home ranges of individuals in the S. ehrenbergisuper-
species, like those of most other subterranean mammals,
are exclusive, defended territories (Nevo 1961, 1979, 1999).
During the breeding season (usually in December –January),
for a brief period, multiple occupancies by both sexes may
occur. Multiple occupancy may also occur during the rais-
ing of the young by females before weaning and dispersion
(from mid-January to mid-March; Nevo 1961). Territories
in S. ehrenbergi,once established and used for one breed-
ing season, usually remain fixed for life except for minor
boundary changes. In general, territories of the young are
established in peripheral areas (Heth 1989; 1991), and ter-
ritories usually do not overlap. During the breeding season,
males leave their territories and usually dig long, straight
tunnels, visible by a straight row of mounds, in search of the
territories and breeding mounds of females. Copulation oc-
curs inside the large female breeding mounds.
Consistent with the predictions of the optimal area hy-
pothesis, the territory size of S. ehrenbergisuperspecies
varies with age, sex, body size, habitat, population density,
and diet; that is, territory size corresponds to the metabolic
demands associated with animal size (Nevo 1961, 1979,
1999; Nevo et al. 1982; Heth 1989). The territories of
subadults are considerably smaller than those of adults, and
the territories of females are smaller than those of males.
Territory size among the species varies with productivity of
the region; it is smaller in highly productive regions (in the
ranges of the species S. galili, 2n52, and S. golani, 2n
54, increasing southward to that of the S. carmeli, 2n 58
species, and climaxing in that of the S. judaei, 2n60 spe-
cies; Nevo 1979, 1991; Nevo et al. 1982). Average territory
sizes in square meters for the four species of S. ehrenbergi
were measured in two ways: (1) direct estimate of territory
size derived from mound distribution (an underestimate),
and (2) indirect estimate of territory size derived from divi-
sion of the area inhabited by mole-rats by number of terri-
tories (an overestimate). For Spalax galili, S. golani, S. car-
meli,and S. judaei,the estimates are (in m^2 ) 60.7 (226.3),
55.3 (246.7), 56.3 (301.7), and 102.7 (329.7) for the re-
sults of method 1 and method 2 (in parentheses). Prelimi-
nary results from radiotracking a female S. galili(2n52)
from the ecologically marginal population of Qiryat She-
mona resulted in a territory size of 63 m^2 (Kushnirov et al.
1998), suggesting the greater accuracy of method 1.
Population density and structure in the four species of S.
ehrenbergihave been extensively studied across the super-
species range along 1,057 km of road transects (Nevo et al.
1982; fig. 47 in Nevo et al. 2001). The results indicated the
following: (1) The overall (but underestimated) number of
mole-rats in their range of 15,500 km^2 in Israel amounts to
1.6 to 2 million individuals. (2) Population density per km^2
for S. galili, S. golani, S. carmeli,and S. judaeiis 140, 177,
101, and 91, respectively, decreasing southward toward
the desert. (3) Populations are largely continuously distrib-296 Chapter Twenty-Five