Do California ground squirrels (Spermophilus beecheyi) use ritualized syntactic cephalocaudal grooming as an agonistic signal?

Animal communication theory holds that many signals have evolved from nonsi gnal precursors. This field and laboratory study of California ground squir rels (Spermophilus beecheyi) provides evidence for the coexistence of such a precursor with its derived display. The precursor is an ancient, endogeno usly sequenced (syntactic) pattern of cephalocaudal grooming movements (CCG s) shared by all rodent suborders. The following evidence supports the hypo thesis that a supernormal version of this pattern has been selected for sig nal function. Syntactic CCGs in the field (a) were more rigidly stereotyped than ordinary syntactic CCGs in the laboratory; (b) differed from laborato ry syntactic CCGs in other ways that enhanced their conspicuousness, in par t through exaggeration of the syntactic cephalocaudal pattern; (c) were ass ociated with scent marking and social staring; and (d) were associated with intrasexual agonistic encounters that did not escalate to fighting.