The main side effect of brumation is that the animal will lose a lot of weight. As a result, it is important to make sure that your turtle has a good diet before they enter into hibernation. Another side effect of brumation is that the animal’s shell will become soft. This is because the turtle is not getting the same amount of calcium that it normally would. As a result, it is important to make sure that your turtle has a good diet and access to calcium before they enter into hibernation.