The total antioxidant capacities (TAC) of feces of mammalian herbivores and carnivores were compared. TAC were estimated using three different methods: 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical (ABTS*) reduction, 1,1-diphenyl-2-picrylhydrazyl radical (DPPH*) reduction, and ferric reducing antioxidant power (FRAP). TAC of 18 herbivorous species were generally higher with respect to 16 carnivorous species [(14.21 +/- 6.72) vs. (9.45 +/- 7.32) mmol Trolox equivalents/kg feces; P < 0.05] in the FRAP assay. The ABTS* reduction assay indicated that the TAC originating from "fast" reacting antioxidants were higher in the herbivores than in carnivores [(17.92 +/- 7.18) vs. (12.22 +/- 8.5) mmol Trolox equivalents/kg feces; P < 0.05], while a reverse trend was observed for TAC originating from "slowly" reacting antioxidants [(20.68 +/- 4.85) vs. (24.68 +/- 6.87) mmol Trolox equivalents/kg feces].