The title "living dead" is very Halloween-appropriate.
And that's exactly what northern leopard frogs are in the wintertime.
Northern leopard frogs are native to northwest Iowa and are aquatic creatures, meaning they live in the water. Like American bullfrogs, which are not native to northern Iowa, northern leopard frogs will hibernate underwater.
They will lie on top of the mud at the bottom of a body of water or partially bury themselves. They will then freeze and thaw right along with their hibernacula --- the place where they hibernate.
As the winter comes on and the area around the frog's hibernacula freezes, ice crystals will also form in the frog's body cavity, bladder and under its skin. The high amount of glucose --- a type of sugar --- in the frog's vital organs, such as its heart, will prevent it from freezing completely.
The partially frozen frog will stop breathing, and its heart will stop beating. It will appear to be dead, but it still is alive.
When the hibernacula warms up above freezing at the end of winter, the frog's frozen body will also thaw, and that will make its heart and lungs start working again.
The frog survives the winter even though it is not breathing through its nostrils, because it can also breathe in another way.
Close your eyes. Now, try to suck oxygen in through your skin instead of your nose.
You can't do it, can you?
Well, frogs can!
Aquatic frogs can actually breathe in two ways. They can take in oxygen through their nostrils and exhale carbon dioxide the same way. However, they can also absorb oxygen that is in water through their skin and release carbon dioxide through their skin.
So, when you hear people talking about zombies and the living dead this Halloween, you can tell them that the real living dead are frogs hibernating in the wintertime.
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