A combination of a flotation/sedimentation experiment and sieve analysis fo
r the reticulorumen (RR) contents of roe deer Capreolus capreolus Linnaeus,
1758, a browsing ruminant, showed that there was no correlation between pa
rticle size and particle density. Large particles were present in both the
sedimented and the buoyant fraction, which is in accord with the reported a
bsence of stratification of RR contents in browsing ruminants. Comparative
sieve analysis of roe deer RR and caecal/rectal material demonstrated that
there must be some selective particle retention in the browsing ruminant as
well, as a certain fraction of large particles in RR contents does not occ
ur in the caecal/rectal material. These results lead to the explanatory dil
emma that, while selective particle retention is observed, it cannot be due
to the mechanisms known to work in grazing ruminants.