Sloths: The unusual hairs from these shaggy heteroclites

Modern sloths, comprising six species within the Bradipopidae and Choloepodidae families, together with the anteaters and armadillos represent an ancient order of distinctive and remarkable placental mammals. Unfortunately, these animals are both endangered and trafficked. Whilst there have been many in-depth studies surrounding the physical and genetic adaptations of sloths required in order to live an almost exclusive arboreal lifestyle, in comparison, literature describing another remarkable feature that they are renowned for – their hair – are somewhat varied in their conclusions. In keeping with their distinctiveness among mammals, sloths exhibit striking and unusual morphological features in their hair. Microscopical images of these features captured using transmitted visible light microscopy and scanning electron microscopy (SEM) are presented, which it is hoped will assist those carrying out forensic wildlife examinations or those called upon to identify the origins of unknown hairs that they may encounter, for example in cultural heritage investigations or animal tracking studies. Although the hairs from Bradipus spp and Choloeps spp exhibit unusual morphology, the results obtained using both laboratory-based and synchrotron-sourced Fourier transform infrared (FTIR) spectrometry indicated that the keratin composition of their hairs did not differ greatly from each other or from that found in other mammals.