None, the rest flew away at the sound of the gunshot. Or one (the dead pigeon).

D. Tomcat

The number of letters of each animal corresponds to the number of the letters in each month. And the first letters spell “Gets Goat”.

January / Giraffe = 7 letters
February / Elephant = 8 letters
March / Tiger = 5 letters
April / Snake = 5 letters
May / Gnu = 3 letters
June / Oryx = 4 letters
July / Anoa = 4 letters
August / Tomcat = 6 letters

Sequoia, eulogia or miaoued are all good options, but there’s an even shorter (and more obscure) word with all the vowels and not a single consonant: Iouea. It’s not the kind of word you’d use at the dinner table, but it’s listed in the Wikipedia dictionary as a genus of Cretaceous fossil sponges.

If you got really tricky and tried to find a word that contained the letters in the phrase ‘all of the vowels’, you probably found, like I did, that there isn’t one. But it was still worth checking.

Billowy.