Shape Analysis as an Additional Tool in Roe Deer (Capreolus capreolus) Management: A New Approach Based on the Relationship between Mandible Shape and Trophic Resources

Abstract

The analysis of body shape variability has always been a central element in biology. More recently, geometric morphometry has developed as a new field in shape analysis, with the aim to study body morphological variations and the identification of their causes. In wildlife management, geometric morphometry could be a useful tool to compare the anatomical structures of an organism and quantify its geometric information in order to relate them to environmental factors, thus identifying the causes and effects of the variation and acting management and/or conservation plans. The aim of our study is to evaluate the relationship between roe deer mandible shape and trophic resources available during autumn and winter. We applied a geometric morphometry approach consisting of a Relative Warp analysis of landmark data in 26 roe deer fawn mandibles. Each sample was assigned to an age category and to an environmental category based on the territory carrying capacity. The mandible shape of samples under 8 months of age is likely influenced by the availability of trophic resources. Our findings suggest that the mandible shape is a reliable instrument to assess resource availability. Geometric morphometry could thus represent an additional tool for roe deer management.

Keywords: geometric morphometry; mandible; roe deer; shape analysis; trophic resources; wildlife management.

Figure 1

(On the top): the consensus configuration for the dorsal side of the mandible (aged 0–8 months). (On the bottom): the caption of the dorsal side of the mandible (aged 0–8 months) from Geogebra. Landmarks are shown in red dots, while semi-landmarks are shown in yellow. Semi-landmarks were placed on the anatomical part encountered by the axis perpendicular to the midpoint of the segment connecting two landmarks.

Figure 2

(On the top): view of the dorsal side of the mandible. (On the bottom): view of the lateral side of the mandible.

Figure 3

(On the top): the consensus configuration for the lateral side of the mandible (aged 0–8 months). (On the bottom): the caption of the lateral side of the mandible (aged 0–8 months) from Geogebra. Landmarks are shown in red dots, while semi-landmarks are shown in yellow. Semi-landmarks were placed on the anatomical part encountered by the axis perpendicular to the midpoint of the segment connecting two landmarks.

Figure 4

RWs (axis 1 and 2) of mandibles pertaining to subjects aged 0–8 months. Deformation grids evidence the sample shape modification along RW1 with respect to the consensus grid linked to the environmental category of the samples. COD 1, 2, 3 indicates the environmental category.