They are nearly all nocturnal, only searching for food at night when the heat is low. They usually do not have sweat glands. Their urine is highly concentrated and their feces are dry. To prevent water loss through respiration, they have a long nose that cools the air and condenses the water inside the nostril before expelling it to the atmosphere. Temperature Regulation Cold Climates Animals that live in water usually take on the temperature of the water, which is usually stable.
Terrestrial reptiles keep their body temperature stable by absorbing solar radiation during the day.
At night they seek shelter to keep warm and to protect themselves during the inactivity that results when they are cooled. Animals that obtain heat from external sources are called ectotherms. Mammals and birds are called endotherms, because they maintain a constant body temperature through metabolism and regulation. Birds use their feathers to protect their bodies. They also migrate to warmer climates.