Courgette teeth marks

Picked loads of courgettes today. Unbelievable as it's only a few days since I picked the previous batch. In that time some of them have grown quite big. Between normal courgette and marrow size. It is these that show evidence of rodent teeth marks. A pair of teeth marks about 5mm wide. Maybe voles?  Anyway they don't penetrate the flesh, just cut through the skin. Are they thirsty or what?  They don't trouble the marrows next to them, or even the smaller courgettes. Just the oversized ones. Never known this before.