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This is the story of how animals hibernate in winter.
Each character in the tale will be represented by a different instrument of the orchestra. For instance, the wood frog will be played by the flute. And here’s the painted turtle played by the bassoon. (Naturally.) The common poorwill by the trumpet. The strings will represent mosquitos. The drums, black bears. And, of course, the Antarctic cod by a theremin accompaniment.
Before we begin—
Hibernation is like sleep… but not really. It’s a period of mental and physical dormancy that varies in species. It just looks like sleep. Because whole new gears are starting to turn inside the body. Metabolism can slow to less than five percent. Heart beats can drop from 300 per minute to less than 10. Hibernation is a reaction of sorts. (Cue archive nature film: “Heavy snows cover the Rockies.”) So when winter comes, hibernation starts. (Archive nature film continued: “Marian again heads for her den.”) But, not just during winter. It also occurs in times of heat and famine. It’s like life support, but instead of machines and doctors, it’s all animal instinct and evolution.
In a snowy wood, in a hole, there sits a wood frog. Its heart is stopped and it’s not breathing. As temperatures drop, the frog freezes. Its body fills with ice crystals. Every winter, like clockwork, the wood frog produces high concentrations of glucose and glycogen in its blood. And something akin to a syrupy antifreeze coats its cells. As a result, its vital organs are protected even though up to two-thirds of the water in the frog’s body is ice.
Just then, a painted turtle breathes through its butt in an ice covered pond—sort of. A hibernating turtle in water slows its metabolism, lowering its energy and oxygen demands. Unable to surface for air, the turtle does something kind of amazing. (Cue turtle solo: “Fiiiiiiiiiiiigaro!”) Instead of breathing through its lungs, it absorbs oxygen from the water by using parts of its body that are thick with blood vessels. That includes its skin, mouth, and (ahem) rear end region.
In an open brush, a common poorwill is completely still. If temperatures drop or insect prey is sparse, the poorwill can slow its metabolic rate and drop its body temperature. It can survive like this several weeks without food. Poorwills are unique among birds for their ability to enter this quieted state for an extended period. Unlike mammal hibernators in their dens, these birds hibernate out in the open—pretty much anywhere.
Suddenly, as cold takes over in a suburban backyard, a male mosquito dies and a female bulks up. Female mosquitoes can gain up to 10 times their weight in preparation for winter. Then they go into a diapause, which—unlike hibernation—is a complete suspension of development.
In a hole in the ground (bigger than the frog’s, of course), a hibernating black bear breaks down fat tissues. This supplies its body with water and up to 4,000 calories everyday. Muscle and organ tissues break down to supply protein. Crazily, the dorment bear continually builds new protein using nitrogen from its urine.
Deep in the dark depths of the Antarctic, a cod is semi-comatose. It has reduced its feeding and slowed its heart rate—20 times less active in winter compared to summer. Winter water lowers the metabolism of many fish, but in the always cold waters of the Southern Ocean, it’s not temperature that triggers the cod’s dormancy—it’s lack of light. Imagine winter in the Antarctic: no sun for months. Without light, it becomes harder to hunt for prey—and harder to survive. Unless, of course, you can hibernate…
The wood frog. The painted turtle. The common poorwill. Mosquitos. The black bear. And, of course, the Antarctic cod.
Ladies and gentlemen, “The Sleep Cycle” by L’orchestre D’hibernation Animaux.
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