It's the standard type of fat used in hibernating hedgehogs
"When a hedgehog is hibernating it is essential that its temperature does not fall below 1°C or it
will suffer frostbite or may even freeze solid. It is obviously unaware of the outside temperature
but if the weather turns very cold, the hedgehog's body brings into play brown fat reserves
which are supercharged fuel boosts. This quickly produced heat is then pumped through the
bloodstream, warming the muscles, causing them to shiver and produce even more heat until
after three or four hours the hedgehog's temperature will have risen by 25°C and its pulse rate
to 320 beats per minute. It will then awake, realise that there is insufficient insulation in its
present nest and move elsewhere to build another one."
Taz