What energy transformation takes place when a animal eats food so they can keep warm?

The energy transformation that takes place when an animal eats food so they can keep warm is chemical energy to thermal energy. This is because the food that the animal eats is broken down into glucose, which is a type of sugar that the body can use for energy. As the glucose is broken down, it releases chemical energy. This energy is then used to heat the body and keep the animal warm.