( ( A ( social animal ) ) ( best ( ( ( kept ( with ( their ( own kind ) ) ) ) ( in captivity ) ) . ) ) )
(ROOT (S (NP (DT A) (JJ social) (NN animal)) (ADVP (RB best)) (VP (VBD kept) (PP (IN with) (NP (PRP$ their) (JJ own) (NN kind))) (PP (IN in) (NP (NN captivity)))) (. .)))
A social animal best kept with their own kind in captivity.
(ROOT (S (PP (IN For) (NP (JJ social) (NNS animals))) (, ,) (NP (NN communication)) (VP (VBZ essential)) (. .)))