A New Method for Quantifying the Asymmetry of Biological Elements by Means of a Photogrammetric Technique Using a Parametric Computer-Aided Design System

Abstract

In the area of zoology, it is of great interest to determine the degree of asymmetry existing in the different animal structures in order to establish it as a variable (biomarker). In this study, a new methodology is proposed for obtaining this variable ‘Asymmetry Index’. Forty-eight Iberian red deer antlers (Cervus elaphus hispanicus) from hunting reserves in the province of Jaen (Spain) have been used. The degree of asymmetry of their antlers between homologous points considered in the two right and left sides of each antler was obtained. The methodology is applied within a parametric Computer-Aided Design system from the photogrammetric restitution of the antler from two photographs. The procedure compares the degree of asymmetry in which the points of each of the right and left sides of the antler are found by means of lengths and angles with respect to an established reference plane based on the geometry of the specimen’s skull. As a result of the study, it has been observed that the Asymmetry Index obtained is lower in those specimens that have a high score in their hunting valuation, so it is considered that this factor can be taken into account as an objective and quantifiable indicator (biomarker).