I would suspect voles(mice with short tails). There has been an explosion in vole numbers on our allotments in recent years. Last year, all my cauliflowers and kale, had their growing hearts eaten out by voles, even though they were covered in small mesh netting.
For this year, I have a constant trapping and baiting program for mice and voles, killing several each week. Not one case of damage by voles.
They are also devils at eating through the growing stems of french beans and runner beans about 75mm above ground.
