The Ontogeny of Expression of Communicative Genes in Coyote–Beagle Hybrids

Abstract

Although there are minimal genetic differences between the coyote (Canis latrans), the gray wolf (Canis lupus), and the domestic dog (Canis familiaris), these three species are extremely different in numerous aspects of their physiology, morphology, and behavior. In particular, the threat display of coyotes differs markedly from dogs and wolves. Coyotes display a wide open mouth gape-threat with attendant arched back defensive posture, and hiss vocalization. In our experience, this threat display is absent from the repertoire of the domestic dog and the gray wolf. We hypothesized that the foundation of these differences in species-typical threat displays is genetic. The threat displays of coyote-beagle crosses (F1's, F2's, F3's, F1F2's and beagle backcrosses), included the following phenotypes: that of each parental species, that of the domestic dog during pre-pubertal development switching spontaneously to the coyote gape-threat following sexual maturation; and a comparable phenotype requiring exposure to post-pubertal social stress-priming to bring the encoded genetic potential for the gape-threat to expression. The changeover from the dog snarl-threat to the coyote gape-threat was accompanied by a precipitous rise in endogenous cortisol levels over baseline. We hypothesized that where alternative genetic systems are physically available, their selective expression in development may depend on environmental events, such as social stress, to affect internal mechanisms that ultimately control the phenotype. Exogenously elevated cortisol levels, in the absence of the subjective experience of social stress, were associated with the onset of the expression of the coyote threat pattern in an F1 hybrid possessing a full haploid complement of coyote genes and his backcross offspring resulting from a breeding to his F2 daughter. With oral doses of hydrocortisone, the cortisol levels were substantially elevated over basal levels. With endogenous cortisol priming, an increase up to five-fold over those levels obtained with social stress was associated with the expression of the coyote phenotype.