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I have received the following questions about winter behavior of alligators. 
Q. Do alligators up north hibernate? Can they breathe underwater?
A. Alligators do not live “up north,” do not technically hibernate and cannot breathe under water. The most northern localities of natural occurrence of American alligators are in North Carolina near Cape Hatteras a coastal habitat with more moderate temperatures than found farther inland. Alligator populations are native to the warmer portions of all coastal states from the Carolinas to Texas and are also found in Arkansas and southeast Oklahoma. They can become dormant and completely immobile under extreme cold conditions.
Q. Alligators presumably cannot live through a winter in northern states. Could global climate change result in warming trends that would let them extend their range into colder regions? Do we need to worry about alligators reaching the Potomac River in northern Virginia near Washington, D.C., where we live?
A. You should place alligators on the bottom of your list of things to worry about anywhere near the Beltway. I am not aware of any definitive studies documenting extensive northern or inland colonization of alligators in response to climate change. They are more prevalent in some regions than they were several decades ago, mostly due to protective regulations that were begun with the Endangered Species Act in the 1970s. This protection allowed alligator populations to increase and to expand their geographic range back to areas they formerly inhabited. 
Alligators are not currently found anywhere in Virginia, although the natural range may have once extended to the Great Dismal Swamp near Norfolk before they were killed off in the early part of the 20th century. Even under the most extreme warming conditions, the big reptiles are unlikely to populate the Potomac River for decades, if ever. 
Q. During the winter, alligators in southern Florida come out to bask on shorelines in the sun on most days, although they seem a bit more sluggish during cold weather than during the summer. What do they do farther north where it gets much colder and lakes can occasionally freeze? I know they are found in the Coastal Plain around Columbia, S.C., Augusta, Ga., and Tuscaloosa, Ala., all of which have at least a few below-freezing days each year. 
A. You are correct that alligators occur naturally in areas where aquatic habitats can freeze over. As with all wildlife that experience extreme weather conditions, adjustments must be made if they are to survive. Some birds, mammals, dragonflies and butterflies migrate seasonally. But all plants and most animals live their entire lives in a single area and have myriad strategies to adjust to cold winters and hot summers. Alligators remain in the water during cold weather and often retreat into dens beneath the bank where air pockets occur. In February 1981, during an unusually cold period in the Carolinas, scientists studying alligators observed a remarkable, never-before-reported behavioral response to the question what alligators do when the entire water surface freezes over. 
John Hagan, Paul Smithson and Phillip Doerr at North Carolina State University first reported the phenomenon. They dubbed it “icing behavior.” I witnessed the behavior during this same cold period. I saw two large alligators in a pond that were in a state of suspended animation with only their noses protruding a few inches above a layer of 4-inch-thick ice. Their bodies were at a 45-degree angle in the water below, which was only 1 to 4 degrees above freezing. 
As with many ecological discoveries, icing behavior turns out to be common and has been observed many times since it was first documented. As evidence of how completely inert an alligator is when exhibiting this behavior, I was able to touch an adult alligator’s snout sticking up through an ice-covered pond. I was pleased to learn they do not move or even open their eyes when one does this. How long alligators can remain in suspended animation is unknown.
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Caption: An alligator covered with duckweed in summer may have to poke its snout through a layer of ice during winter cold spells. Photo courtesy Trip Lamb