As the days get shorter and the temperature drops, this bear to get ready for hibernation.

As the days get shorter and the temperature drops, this bear overeats and stores food as fat to get ready for hibernation.

When hibernate, bears will keep sleeping so they won't get any food from outside so they need to collect the food before hibernating. They have to eat more food than usual and stored it as fat to keep them from starving. The fats also help keep them warm as they are insulating the heat.

Gravitational force i believe