How do you keep squirrels from digging up bulbs?
How Do Keep Squirrels From Digging Up Bulbs
Thee following articles should be of help: https://www.gardeningknowhow.com/ornamental/bulbs/bgen/protect-flower-bulbs.htm
A couple of notes. If you use the layers of sharp gravel, use 1.5 - 2 inches. If you use things like blood meal, hair or spray on deterrants, be aware that with time or rain, these become ineffective. We have found that live-trapping is a waste of time.