Zur Kenntnis des Stimmapparates der Epauletten-Flughunde (Epomophorini, Pteropodidae, Megachiroptera)

Courting males of Epomophorus, Epomops and Hypsignathus emit loud calls attracting estrous females. The organs of vocalization of a male Epomophorus labiatus and of a female Epomophorus anurus were studied as well as male and female Epomops buettikoferi and H. monstrosus with special emphasis on the topography of the neck and of the thoracic cavity. Compared to other Megachiroptera the larynx of the 3 genera is enlarged to a quite different degree. Epomophorus is close to the supposed ancestral condition. The larynx is situated in the caudal half of the neck. There is no sexual dimorphism in the size of the larynx. The males of H. monstrosus possess a huge larynx reaching caudally to the diaphragm and nearly filling up the upper and middle mediastinum. The larynx of the females is much smaller reaching only behind the manubrium sterni. Epomops is intermediate between Epomophorus and Hypsignathus. The male’s larynx is larger than that of Epomophorus and partially situated in the thoracic cavity. In Hypsignathus the larynx enters the thoracic cavity ventrally, but in Epomops dorsally of the heart. To reach the bifurcation the trachea is curved cranio-dorsally in Hypsignathus, but cranio-ventrally in Epomops. The different topography of the thoracic organs demonstrates that the enlargement of the larynx took place independently in the phylogeny of both genera. The extreme enlargement of the larynx in the male H. monstrosus can be regarded as a result of intraspecific selection in correlation with the highly specialized lek mating behavior of this species.