actually there is two others, y and w can be used as a vowel also
One animal name without a "classic vowel" (AEIOU) is lynx. But the Y is a vowel in this use.
CANADA!
angst
any vowel after the fourth vowel
The answer is not the obvious "e" the word Vowel in it self is "vowel" being 6th, so it is the letter a.