protect bulbs from moles/voles
Moles do not typically eat tulip bulbs. It is voles that eat the bulbs. I don't know of any treatments for the bulbs however you can work to get rid of the voles. Here is the MU Guide G6445 Controlling Voles in Horticulture Plantings and Orchards http://extension.missouri.edu/p/G9445 This guide gives some good ideas on how to control them.