Why the populations decrease between july and december

There are two reasons that seem logic from this graph. First, towards the winter, the animal population decreases as some of them die or emigrate from their ecosystem. And the second main reason is that the breeding stock is not active toward th months of July to December, so as there are no breeding stock, then less animal population may born by that time

The answer is energy. the arrows are showing how exited and energized the stones are.