i had a mouse, if u get a mouse trap whatever u do DON'T USE CHEESE!!! cos it just slides straight off the pin. use something sweet & stickey like fruitella!. cos they can't get it off. theres always more than one mouse so once u've got one put the trap out again & leave it until u catch another & another & another cos they will be about. mice are good climbers & they weigh less than u would think. when they ate my leaves they ate from the centre like yours in the picture. another thing to watch out for is they dig ip the soil for no reason & exposed my roots to light. i advise u get rid of whatever it is & fast!
hope this helped.