If you suspect that a deer or rabbit is eating your plants, a close look at the damaged plant often reveals the culprit. Look where the plant was bitten. Is the damaged edge clean-cut or ragged?
A neatly clipped plant is a tell-tale sign of rabbit feeding. Often, the cut is angled at 45 degrees.
Rough or ragged damage was most likely caused by deer. Deer don't have upper incisors (teeth in the front that snip) so they pull and rip their food.
If leaf damage consists of small holes or chewed areas, you likely have slug or insect damage. The University Minnesota Extension webpage What's Wrong with My Plant? can help you diagnose the problem and suggest treatments.