Where Do Those Cold-blooded Animals Go in Winter?
February 13, 2009
I love a New England winter. With snow falling and wind raging outside, I’m inside with hot chocolate in hand, curled up in my puffy chair, and snug-as-a-bug-in-a-rug. What’s that? Is a bug actually snug in a rug? Better not be in my rugs! Bugs and other creatures are outside in the elements, not in my rugs I hope.
So how do cold-blooded creatures cope with this season, anyway? First of all, let’s be clear on what, “cold-blooded” means. This is actually an inaccurate and outdated word. We’re talking about animals that get their heat from their environment, like amphibians, reptiles, insects and other arthropods, and fish. We call them “ectothermic”, meaning literally, “outside heat”. These creatures seek out warm places or cooler places in order to stay just the right temperature. The benefit of being ectothermic is food. They don’t need to eat nearly as much as mammals and birds who need to fuel that fire within. Going without eating for a few months therefore works for them; winter’s cold though is a challenge.
I’ve compiled a few ectothermic animals and their amazing adaptations for surviving winter. These over-wintering strategies have developed over a long period of time enabling generation after generation to carry on from year to year.
Yellow-jackets and Hornets: During summer months, a whole colony of sterile female workers are busy hunting for insects, raising young and caring for the colony while the queen lays eggs. Toward the end of the season, the queen lays eggs that develop into fertile females and males, who, once mature, mate. The fertilized females are the only ones who over-winter; every other colony member dies. Each female may find a bark crevice, rotten log, or pile of leaves to hide in. These queens single-handedly start a new colony next spring.
Mosquitoes: Mosquitoes from temperate regions have varying winter strategies. The adults of some species die, after leaving cold-hardy eggs that over-winter under ice. When the water warms in spring, the eggs will hatch. In other species, females who have mated in the fall will hibernate in a hollow log, your basement, or other secure place. This location does not have to stay above freezing, as the insect produces glycerol, which infuses its body and acts as a natural anti-freeze. Amazing.
Aquatic Frogs: Aquatic frogs, like leopard frogs, green frogs or American bullfrogs, spend the winter underwater in a low energy state. During this time, they have to breathe through their skin, so they cannot be buried deep in the mud where the oxygen content is low. They need to be where the water still has plenty of oxygen, so incoming streams and rivulets may be good places for them to be.
Terrestrial Frogs (Toads): The American toad is a good digger. It digs itself a deep burrow in which to over-winter below the frost line. Spring peepers and wood frogs cannot dig so well, and find themselves a crevice in which to sleep away the winter. The amazing thing is, the fluid in their bodies can freeze – without doing harm to the animal. Again, a natural antifreeze – glucose – infuses the vital organs, preventing ice crystals from piercing cells and body organs, and dropping the freezing point of water. A partially frozen frog wakes up in the spring none-the-worse for wear.
Snakes: Snakes spend the winter in a rock crevice, animal burrow, or deep hole under a root ball. It is necessary that this den be below frost level. Since there may not be many of these locations, many snakes oftentimes den together. Some garter snakes may number in the hundreds – or thousands – in a single hibernaculum, or winter den. Copperheads, black rat snakes and rattlesnakes commonly den together.
Each organism has a way of coping with winter’s challenges. During this time, life is certainly on-the-edge. Cold snaps can be disastrous. Still, amazingly, there are those who survive. The next time you are snuggled in your hibernaculum, think about some of those creatures outside who are awaiting the warming rays of spring sunshine..
About the Author:
Nancy Condon is an award-winning Environmental Educator, cross-country canoeist, hike leader, fan of National Parks, and co-founder of NaturePods, Guides for the Nature Traveler. For unique programs to download to your iPod before you travel or explore the outdoors, visit NaturePods.