American alligators hibernate during the winter in burrows (or "dens") that they construct, but may occasionally emerge during brief spells of warmer weather.Another discussion at from the Everglades National Park factsheet:
Alligators do not feed during the cooler months. Studies in captivity have shown that alligators generally begin to lose their appetite below 27°C (80°F), and stop feeding altogether below 23°C (73°F). They can easily last the winter on their energy reserves.
Adult alligators can survive freezing conditions if they are in water. They submerge their body but keep their nostrils projecting above the water surface, so that when the surface freezes they can still breathe (called the "icing response"). Essentially their upper body becomes trapped in the ice. However, occasionally alligators may be trapped completely below ice, and have been known to survive for over 8 hours without taking a breath, because the freezing water slows their metabolic rate down to very low levels. Yet another example of their amazing ability to survive. Crocodilian Species - American Alligator (Alligator mississippiensis)
"Alligators are cold-blooded, which means that their body temperatures fluctuate in response to the temperature of their surroundings. An advantage of being cold-blooded is that little energy needs to be spent in maintaining a high body temperature, and therefore less food is needed. A healthy alligator can go many months without food. Alligators can survive in water temperatures as cold as 36°F (2°C) and as warm as 98°F (38°C), however they function best within a relatively narrow range of temperatures." Formerly www.nps.gov/ever/eco/gator.htmAs for Caimans little info seems to be available.