( ( They ( usually ( ( ( ( ( live alone ) ( in swamps ) ) , ) and ) ( are ( ( generally ( the ( ( most dangerous ) predator ) ) ) ( in ( the area ) ) ) ) ) ) ) ( they ( inhabit . ) ) )
(ROOT (S (S (NP (PRP They)) (ADVP (RB usually)) (VP (VP (VBP live) (ADVP (RB alone)) (PP (IN in) (NP (NNS swamps)))) (, ,) (CC and) (VP (VBP are) (NP (NP (RB generally) (DT the) (ADJP (RBS most) (JJ dangerous)) (NN predator)) (PP (IN in) (NP (DT the) (NN area))))))) (NP (PRP they)) (VP (VBP inhabit)) (. .)))
They usually live alone in swamps, and are generally the most dangerous predator in the area they inhabit.
(ROOT (S (NP (DT A) (JJR fewer) (NNS predators)) (VP (VBZ is) (ADJP (RBS most) (JJ likely) (S (VP (TO to) (VP (VB cause) (NP (NP (DT the) (NN number)) (PP (IN of) (NP (NP (NNS rabbits)) (VP (VBG living) (PP (IN in) (NP (DT an) (NN area))) (S (VP (TO to) (VP (VB increase))))))))))))) (. .)))
A fewer predators is most likely to cause the number of rabbits living in an area to increase.