Mice and rats eat anything from veggies to plaster board to stay alive.
If you suspect it's a mouse stealing the strawberries then put out a
mouse trap and use peanut butter for bait, mice and rats can't resist
the smell of peanut butter. If the mouse traps are untouched and the
strawberries are still disappearing it could be hungry birds. I lose 90%
of my raspberries to birds. I once bought bird netting to protect my
raspberries but I found some birds had got stuck in the netting, I did
away with the netting.