Fluid and particle passage in three duiker species

Ruminants are characterised by two different types of reticulorumen (RR) physiology. ‘Cattle-type’ ruminants have, amongst other features such as RR contents stratification and a heterogenous intraruminal papillation, a distinct difference between the mean retention time (MRT) of small particles and fluids (the ratio is called the selectivity factor, SF). ‘Moose-type’ ruminants have RR contents that are less stratified, a more homogenous intraruminal papillation and low SFs, indicating less difference in the MRT of small particles and fluids. To date, physiological data indicating a ‘moose-type’ physiology have only been measured in giraffids and Odocoilean cervids, raising the question whether it is limited to these taxonomic groups only. Here, we measured MRTs of fluids and particles in five duikers (Bovidae, Cephalophinae) from three species (Sylvicapra grimmia, Cephalophus monticola and Cephalophus sylvicultor) and found SFs in the RR of 1.27±0.18 — well within the range of these other browsers. These results are the first physiological indication that a ‘moose-type’ physiology may also occur in bovid species and thus might represent a true convergent adaptation