The mice were fattened in a special vessel (https://en.wikipedia.org/wiki/Glirarium https://en.wikipedia.org/wiki/Glirarium) which tricked them into preparing f

The mice were fattened in a special vessel (https://en.wikipedia.org/wiki/Glirarium https://en.wikipedia.org/wiki/Glirarium) which tricked them into preparing for hibernation, which fattened them up significantly. Still probably not a lot in them.