Gross morphology, radiology and computed tomography of the ear of the southern white rhinoceros (Ceratotherium simum simum)

Abstract

Since 2008 there has been a dramatic increase in poaching of rhinoceroses in Africa. Today, the southern white rhinoceros is classified as Near Threatened with less than 20000 individuals left. The ear of the rhinoceros appears to be an important organ in the animal’s behaviour and thermoregulation, in population management and also for clinical use. Despite its important roles, there is currently only fragmented information available concerning the rhinoceros's gross ear anatomy as well as radiographic and computed tomographic (CT) anatomy. The aim of this study is to fill this void describing the gross, radiographic and CT anatomy of the ear of the southern white rhinoceros following the standard international veterinary anatomical nomenclature. We used seven intact ears belonging to four southern white rhinoceroses (3 cadavers plus 1 clinical case) of different age (from neonate to adult) to perform radiographic, CT and micro-CT studies before dissecting four of them. We described the gross anatomy of the cartilages, muscles, particular vessels of the ear and associated organs, we presented radiographic views and CT protocols that can be used to assess this region as well as the imaged structures, and we reported on the microanatomy of the southern white rhinoceros ear using micro-CT, allowing tridimensional virtual models of the middle and inner ears to be displayed. The findings of this study will be useful to anatomists, radiologists and wildlife veterinarians, and will also hopefully pave the way for further research providing even more detail of this fascinating but difficult to investigate region.