How do animals store long term energy? why?

They store it as fat

Explanation:

proteins and carbs can both be converted into fat inside the body. When an animal eats more food than needed, the extra gets converted into fat and stored in adipose cells. During times with low amounts of food, the body can convert the fat into usable energy.

image result for how many calories of energy will 20 grams of carbohydrates provide in one gram provides 4 calories

consuming the right balance of protein, carbohydrates and fat can you maintain a healthy weight and optimize your energy levels. protein and carbohydrates both contain 4 calories per gram, while fat provides 9 calories per gram.