“And they came (the pure creatures) to the ark seven by seven, male and female”
G-d’s command was that only the pure (kosher species) creatures be taken seven each of male and female, yet the impure creatures (non-kosher species) be taken only two each, male and female each…
This shows that Hashem embued within each creature the understanding that each knew or understood that he/she was either a pure or impure creature, for the Torah had not yet been passed down to the Jewish people.