Nature Notebook – Woodchuck Hibernation
A few woodchucks are still trying to pack on pounds at our feeders. The fatter the woodchuck, the less time it spends in hibernation. That nearly dead state, although good for energy use reduction, has negative effects.
The nervous system is depressed so a woodchuck in deep torpor (hibernation) is less sensitive to stimuli and cannot arouse quickly enough to respond to threats from predators. Memory retention is also affected which is especially dangerous for male woodchucks. They emerge in February to survey their territory for female woodchuck dens locations then return to finish napping. Forgetting where their own dens are can prove fatal.
The immune system is similarly depressed so the animal is more vulnerable to infections and parasites. The very low breathing rate drastically reduces the amount of oxygen in its tissues. Muscle mass is reduced as is the development of reproductive organs (especially for males).
If a woodchuck is fat enough (has enough energy stored away), it can keep its body temperature much warmer and avoid those nasty consequences. They can spend more time in a sleep state, rather than deep torpor, which allows its normal physiological processes to continue.