Bisoniana 100. Variability of the skull shape in hybrids between European bison and domestic cattle

Abstract

The study was carried out on 59 (28,31) skulls of hybrids between European bison and domestic cattle of the Polish red breed and black and white lowland breed. The percentage of cattle's blood increased from 50% in F1 generation to 93.75%, in three backcross generations. In order to compare the data for hybrids, 40 (6,34) skulls of domestic cattle were measured and the data for European bison were taken from literature. Adult F1 hybrids exceeded both European bison and the cattle as well as backcross hybrids in basal length of a skull, length of dorsum nasi and mandibula, and in capacity of cavum cranii. Most remaining cranial dimensions in F1 hybrids and the shape of F1 male skulls were intermediate between the parental forms. The features of European bison which distinctly predominated in hybrid skulls were: the breadth of occiput, the size and shape of processus cornuales in F1 hybrids of both sexes as well as telescopic annuli orbitales and the height of a skull in F1 maIes. The cattle features predominated in: the skull shape of F1 females and backcross hybrids, calvaria formed entirely of ossa frontalia, composition of planum nuchale, hind situation of processus cornuales, and the height of fossa temporalis. The growth rate of F1 hybrids skulls during the second year of their life was faster than that in European bison. However, in European bison which were older than 4 yrs breadth dimensions of a skull grew more intensively than in cattle. Sexual dimorphic features in hybrid crania occurred in the calvaria and planum nuchale and in the size of processus cornuales. In adult hybrids the variability of linear cranial dimensions was rather low whereas structural differentiation was higher. In backcross hybrids the skulls became more similar to those of the cattle as the percentage of cattle's blood increased.