I have a couple of clematis which I had been neglecting for a few years; they haven't had any support so were trailing on the ground.
This year, as they came up and the stems had grown out to a foot or two long, I trained them onto trellises. Within about a week, I found that all the stems had been neatly cut, looking almost like knife cuts about 4 to 6 inches above the soil level. There was no evidence of chewing or any other damage, no sign that anything had been eaten, just neat cuts, which basically killed off all the foliage.
What did this? Rabbits? Why were they merely cut and not eaten?