Whether in a pot or in the soil. I used to use a small piece of small holed chicken wire bent over the top of the pot, to ensure the blighters couldn't get in. The same thing with the soil, but I used to create a little frame out the wire. Enough to cover the area, then bent the sides down, so about 2" high and secured with tent pegs or large wire hooks to ensure the wire couldn't be lifted.

I do the same, but hold the wire down with rocks as we have very stony soil.
Or you could try sprinkling chopped chillies (dried seems to work OK) around the bulbs.

i actually bury the chicken wire over the top so i dont see the wire.