INTRASPECIFIC COMBAT AND THE EVOLUTION OF THE CAPRINI

Abstract

Among the animals belonging to the mammalian tribe Caprini (sheep and goats), intraspecific conflict between males often takes the form of violent head-to-head butting. This paper correlates differences in fighting behavior among the various genera with the relative development of the neck muscles in each. Fighting style and horn shape are analyzed with reference to the production of torques about the occiput which, if unopposed, would cause violent and injurious rotation of the head. Areas of muscle insertion on the skull were used as the major indicators of muscle size, but dissections were also performed. Further studies of both musculature and behavior are desirable to clarify details which remain obscure. The tribe Caprini is composed of five genera: Hernitragus, tahr; Capra, goats, ibexes; Amnmotragus, Barbary sheep; Pseudois, blue sheep; and Ovis, true sheep-mouflons, argalis, and bighorn. All of these animals possess large, massive horns which are used to deal and receive blows of considerable force. In contrast, their ancestors are believed to have resembled the living Rupicaprini (Pilgrim, 1939; 1947), light-limbed creatures with small horns, quite aptly referred to as goatantelope (McCann, 1956). Rupicaprini are not adapted to withstand, nor do they engage in, the furious head-on collisions of male caprines. Instead, horn-locking and head-to-head pushing occur, along with some body-butting (Couturier, 1938; Geist, 1964; 1966b). Such behavior is considered to be ancestral to the patterns observed in the Caprini (Geist, 1966b). Evolution in the latter group has thus involved alteration of both behavior and morphology, and