Animal in itself is a pretty useless tag. The only things that imply it are random tags that happen to contain the word animal, not any actual animals themselves. This makes no sense.
If you try to make it into an umbrella tag for all animals, then you quickly run into problems. Like do insects count as animals, or do fantasy creatures like dragons or RPG monsters count, or does it count when the animal is barely present, like a bird that's a tiny speck deep in the background? These are all signs the tag is too broad. We got rid of vehicle for similar reasons; it made no sense to have an umbrella tag for everything from bicycles to space craft.