( They ( ( have ( ( a ( ( very strong ) odor ) ) ( which ( is ( characteristic ( of ( their dens ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP have) (NP (NP (DT a) (ADJP (RB very) (JJ strong)) (NN odor)) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (ADJP (JJ characteristic) (PP (IN of) (NP (PRP$ their) (NNS dens))))))))) (. .)))
They have a very strong odor which is characteristic of their dens.
(ROOT (S (NP (JJ Strong) (NN odor)) (VP (VBZ helps) (S (NP (DT some) (NNS animals)) (VP (VB defend) (NP (PRP themselves)) (PP (IN against) (NP (NNS predators)))))) (. .)))
Strong odor helps some animals defend themselves against predators.