slugs and snails do this a lot in my garden so I suspect this is the culprit. I have gone out in the early morning and found 4" slugs having breakfast.

Some of my daffs are decimated every year by slugs/snails. it's so disappointing isn't it? i often go out with a torch at night and find numerous slugs feeding away. In the compost bin they go. They are mainly those little beige ones. The odd snail too, which i don't put in compost bin in case they can't out.

I had these & they looked just like yours :o((