Modélisation du dimorphisme sexuel chez la chèvre de race Arabia en Algérie (Capra hircus L., 1758) : étude ostéométrique prédictive de têtes osseuses

The creation of references for zooarchaeology is of the highest interest in order to be able to accurately identify the bones left from archaeological excavation sites. Craniometry in the caprine species is lacking and this work proposes, focusing on sexual dimorphism which is an important diagnostic factor, to deepen a rustic breed of medium size, the Arabia breed of the region of Constantine in Algeria. A balanced sample of 30 males and 30 females of adult-sized (animals older than 2 years) was collected and the skulls and mandibles of each animal were measured. A total of 16 measurements were made on the skull, 8 on the mandible and 4 ratios (index) were calculated (2 for the skull and 2 for the mandible). Univariate analyses provide reference values. The overall variability of the entire population for the different parameters ranges from 5.8% (CB14) to 16.3% (MH9). The parameters of the skull are more variable than those of the face with mean values of coefficients of variation equal to 9.2% and 8.7% respectively. Multivariate analysis (Principal Component Analysis or PCA) clearly highlights sexual dimorphism : sex segregation is observed in the main factorial plane and the clouds of the points of the males and female individuals are distinguished mainly on the axis I (size axis). The 95% confidence ellipses do not overlap. The discriminant analysis made it possible to propose a list of variables allowing to separate the two sexes at best. The step-by-step analysis highlights as the most discriminant value CB19. As a result of the logistic regression made, it was possible to propose threshold values in order to separate the males from the females for the 16 measurements with an error rate of less than 0.40.