deer and rodents (squirrels, ground hogs, etc) and rabbits like some bulbs. not sure about the green parts tho. they don't like iris tho.
slugs love iris they eat the tubers and the bottom parts of the leaves tho...and they eat holes out of the leaves, not how you're describing what is happening.
maybe it's oppossum? or raccoon? a neighbors cat?
you could try spraying the leaves with a mild soap solution or some hot pepper. you'd have to reapply after a rain, tho.
