The ratio’s of reticulo-rumen volume to body mass were determined for all four species in addition to rumen pH, fermentation rate and VFA concentration. Information on rumen and faeces dry-matter percentage is also reported. Only the blue wildebeest exhibited a marked decline in body mass in winter. In summer the rumen fermentation on average for eight blue wildebeest studied, was 327 μmol gas/g DM/h, much higher than the other species including springbok with 269 μmol gas/g DM/h. This same trend was seen in winter. The theory that wildebeest are less well adapted to the arid region than the other species investigated is further supported by the fact that in both seasons the DM% was substantially lower than in the other species.