However, in a recent analysis, Clauss et al.
(2007a, in press) argued that for mammalian herbivores gut-residence
time of food is less impacted by body size than previously thought,
suggesting that oft-cited models defining herbivore constraints (e.g.
Parra, 1978; Demment and Van Soest, 1985; Illius and Gordon, 1992;
Cork, 1996) may be inappropriate for large mammalian herbivores.
Instead, interactions between food intake (rather than body mass) and
food residence time (i.e. mean retention time; MRT), may be more
important for understanding the evolution and ecology of large