This is the 1004th most frequent Polish word.
zwierząt
"Zwierząt" means "of animals" (genitive plural form of "zwierzę").
Here, "zwierząt" is used in genitive plural to indicate the possession or relationship of 'animals'.
W ogrodzie zoologicznym jest wiele różnych zwierząt.
In the zoo, there are many different animals.
This usage of "zwierząt" in genitive plural indicates a partitive relation, emphasizing the group of 'wild animals'.
Nie powinno się dotykać dzikich zwierząt.
One should not touch wild animals.
In this sentence, "zwierząt" is in genitive plural form to match the grammatical structure required by the noun 'species' (gatunków).