To deter squirrels from digging or eating your tulips:
1. Plant your tulip bulbs 8 inches deep. Place chicken wire on top of them and then cover with soil.
2. As soon as the temperature is above zero in the spring and there is some growth, spray them with a couple squirts of Plantskydd. An OMRI certified product which does not wash off when it rains. This product deters them from eating the blooms. It also works for preventing deer from eating any of your plants.