THE PASSAGE OF DIGESTA, PARTICLE-SIZE, AND IN-VITRO FERMENTATION RATEIN THE 3-TOED SLOTH BRADYPUS-TRIDACTYLUS (EDENTATA, BRADYPODIDAE)

The digestive physiology of six three-toed sloths (Bradypus tridactylu s) fed exclusively on Cecropia palmata foliage was studied. The mass o f digesta in the gut was between 17 and 37% of body mass. This was bet ween 133 and 282% of that expected in an animal of this size, based on published allometric equations. The concentration of total short chai n fatty acids in the stomach was similar to that in the fermentative r egions of other foregut fermenting herbivores but the rate of fermenta tion measured in vitro was very slow (6-12 mmol.l(-1).h(-1)) and subst antially lower than that observed using similar techniques in other sm all foregut fermenters. The overall (dose to excretion) mean retention time of particulate and solute digesta markers was about 150 h. Most of this (73%) occurred in the stomach but a substantial proportion (17 %) could be attributed to the storage of faeces in the rectum. The slo w rate of passage of digesta through the gut together with the slow ra te of fermentation in the stomach is not typical of small foregut ferm enting herbivores. However, such a pattern is feasible in Bradypus tri dactylus because of the large volume of digesta retained in the gut an d the very low metabolic rate of these mammals.