Skull sexual dimorphism appears in toy rabbits

Abstract

The aim of this paper was to use geometric morphometrics to study the skull sexual dimorphism of toy rabbits, which present paedomorphic (babyness) traits comparing data with those from agriotype (ancestor), Oryctolagus cuniculus. For this purpose, we examined 43 post-weaned corpses belonging to wild rabbit (n=22, 7 ♂ and 15 ♀, 1295.6 ± 333.8 kg of body weight and 88.0 ± 1.12 cm of ear length) and toy type (n=21, 4 ♂ and 17 ♀, short and upright ears, 1031.3 ± 644.13 kg of body weight and 6.2 ± 1.08 cm of ear length). Heads were radiographed using a Potro® machine on a latero-lateral projection and 7 landmarks were located on the skull and studied by means of geometric morphometric procedures. Size and shape between genders appeared statistically different only for toys, mainly focused on splanchnocranium (face) for shape. Detected sexual dimorphism could be attributed to selection arising from differential mating success, or sexual selection, due to human management. Moreover, the inconsistency with Rensch's hypothesis - which establishes that males in larger species will tend to be larger relative to females than in smaller species- allows us to suggest that Rensch's hypothesis is not necessarily followed in artificial selection experiencing miniaturization in body shape. It must be outlined the opportunities to tackle paedomorphic questions via geometric morphometrics methods in toy rabbits.