The scaling relationship between body weight and fermentation gut capacity presumably impacts dietary patterns of ruminants. Interspecific scaling relationships between body weight and fermentation gut capacity have a slope of 1.0 (isometric scaler) when body weights span ≥3 orders of magnitude. Isometric scaling relationships between body weight and fermentation gut capacity also have been suggested to explain dietary patterns within species, but whether scaling relationships are isometric within a single species is unresolved. We determined if the intraspecific scaling relationship between body weight and fermentation gut capacity was isometric for axis deer (Axis axis) and assessed the influence of reproductive status of females on the scaling relationship. We collected 8 adult male and 21 adult female axis deer from January 2004 to April 2005 at a private ranch in Bastrop County, Texas. Capacity of the rumen–reticulum, cecum, and colon, organs where fermentation occurs, was estimated by calculating wet weight and volume capacity. Forage quality, month that animal was collected, and sex did not influence scaling relationships. Regressions apparently had isometric scalers for fermentation gut capacity but the relationships were not strong, in part because females that were pregnant had smaller fermentative gut capacities than nonreproductive or lactating animals.