It has teeth marks. I don't think it's something getting out.
Squirrels and rats are still the most likely I think if no mice droppings. Have a look behind your kitchen kickboards maybe? I don't know how often squirrels defecate but do know my mother-in-law had a squirrel problem years ago. They ate some of her Christmas cake.
Many years ago a friend came downstairs one morning to find an apple had been nibbled on the fruit bowl. She thought it was one of the children although it was denied. Next morning another partly eaten piece of fruit. Before the day was over she saw a large rat scurrying round the kitchen.
She’d recently had a new kitchen fitted and the kitchen fitters left a small gap around the pipe under the sink .
Rats would be my first thought. They are clever little devils. They like to eat lemons on the tree but leave half of them uneaten. Otherwise some sort of wasp?
Thanks everyone for suggestions. We pulled the cooker out and checked behind it. Emptied the cupboards and checked for holes/droppings. Nothing. Left the avocado out overnight with lots of traps around. Undisturbed this morning. Hoping Allira is right and whatever ate it is suffering acute indigestion, won’t be back and has also told all its friends to stay away.
More likely a rat because they tend to hide their droppings. My Mum kept losing her bathroom soap. One day she was lying in the bath and a rat popped up behind the bidet. When she looked she could see a hole and loads of soap!
Just a warning if you suspect squirrels rats or mice get pest control in ASAP. My next door neighbour hand reared a squirrel and kept it as a pet when I was very young. Will never forget the sight of her in pouring rain with only a dress on and one shoe watching her home go up in flames. The squirrel started the fire chewing through electric wires. My gran brought her an umbrella coat and shoes while she waited for the fire brigade.