Certified GKH Gardening Expert
This one may be difficult to pinpoint since you haven't yet seen the culprit. Tulips are a favorite of deer and will normally devour the entire plant, leaves and all. Rabbits are known to munch on the leaves too. Most other rodents typically feast on the bulb itself. Have you noticed any tracks or droppings? This can give you a clue as to which animal it is. These articles may help determine the pest in question, or at least provide suggestions for alleviating the issue: https://www.gardeningknowhow.com/plant-problems/pests/deer/deer-repellents.htm, https://www.gardeningknowhow.com/plant-problems/pests/how-to-keep-rabbits-out-of-gardens.htm, https://www.gardeningknowhow.com/plant-problems/pests/animals/camouflage-gardening-deterring-garden-crashers-pests.htm
