Ruminants are characterised by an efficient particle sorting mechanism in the forestomach followed by selective rechewing of large food particles. For the non-ruminating foregut fermenter pygmy hippo it was demonstrated that large particles are excreted as fast as, or faster than, the small particles. The same has been suggested for other non-ruminating foregut fermenters. We determined the mean retention time of fluids and different sized particles in six red kangaroos (Macropus rufus), seven collared peccaries (Pecari tajacu) and three colobine monkeys (Colobus angolensis, C. polykomos, Trachypithecus johnii). We fed Co-EDTA as fluid and mordanted fibre as particle markers (Cr, Ce). Mean (± SD) total tract retention time for fluids, small and large particles was 14±2 h, 29±10 h and 30±9 h in red kangaroos, 26±2 h, 34±5 h and 32±3 h in collared peccaries and 57±17 h, 55±19 h and 54±19 h in colobine monkeys, respectively. Large and small particles were excreted simultaneously in all species. There was no difference in the excretion of fluids and particles in the colobine monkeys, in contrast to the other foregut fermenters. In the non-primate, non-ruminant foregut fermenters, the difference in the excretion of fluids and small particles decreases with increasing food intake. In contrast, ruminants keep this differential excretion constant at different intake levels. This may be a prerequisite for the sorting of particles in their forestomach and enable them to achieve higher food intake rates. The functional significance of differential excretion of fluids and particles from the forestomach requires further investigations.