( ( As ( an herbivore ) ) ( , ( ( these ( large mammals ) ) ( ( eat ( only plants ) ) . ) ) ) )
(ROOT (S (PP (IN As) (NP (DT an) (NN herbivore))) (, ,) (NP (DT these) (JJ large) (NNS mammals)) (VP (VBP eat) (NP (JJ only) (NNS plants))) (. .)))
As an herbivore, these large mammals eat only plants.
(ROOT (S (NP (NNS Herbivores)) (VP (VBP are) (NP (NP (NNS heterotrophs)) (SBAR (WHNP (WDT that)) (S (VP (VBP eat) (NP (UCP (ADJP (JJ only)) (CC or) (ADVP (RB mainly))) (NNS plants))))))) (. .)))