Rodent Societies: An Ecological & Evolutionary Perspective

species) is intimately associated with behavioral genetic

variables of activity, exploration, habitat choice, and ag-

gression patterns. These behavioral patterns contribute col-

lectively to the optimized energetic balance between and

within species; hence, increased fitness (Nevo 1999; Nevo

et al. 2001).

Evolutionary patterns and theory of aggression in Spalax

Aggressive behavior (fig. 25.2) is largely innate and geneti-

cally polymorphic (fig. 25.5a –b) in solitary, territorial sub-

terranean mole-rats (Nevo et al. 1986). The pattern of

aggression between individuals of the same species is qual-

itatively similar, but quantitatively different from aggressive

patterns between individuals of different species. The prox-

imate cues eliciting aggressive behavior in blind mole-rats,

where visual stimuli do not operate, are seismic, olfactory,

auditory, and tactile cues — apparently in this order (Nevo

1990, 1999; Nevo et al. 2001). The ultimate interacting

determinants causing variation in the pattern and intensity

of aggressive behavior among individuals, populations, and

species of Spalaxinclude genetic, ecological, demographi-

cal, life-history, and ethological factors, as follows.

Genetically,aggression generally increases with genetic

relatedness both within and between species (fig. 25.5d).

However, within populations the levels of aggression vary

Evolution of Pacifism and Sociality in Blind Mole-Rats 299

Figure 25.5c Geographic clinal variation in the three major behavioral aggres-
sive phenotypes across the four species of the Spalax ehrenbergisuperspecies
in Israel: Spalax galili, 2 n52; S. golani, 2 n54; S. carmeli, 2 n58, and
S. judaei, 2 n60, in each sex separately (from Nevo et al. 1986).

Figure 25.5d The relationship between intermale “total aggression” and genetic relatedness within and between spe-

cies of the Spalax ehrenbergicomplex. “Total aggression” is the sum of the number of attacks, bites, head-ons, and

sniffings with open mouth. Genetic relatedness was estimated by geographical distance; i.e., we assume that the further

apart the populations and species, the lower their genetic relatedness.