Cold-blooded creatures take on the temperature of their surroundings. They are hot when their environment is hot and cold when their environment is cold. In hot environments, cold-blooded animals can have blood that is much warmer than warm-blooded animals.
Reptiles are cold blooded. Cold blooded means that there is no internal mechanism, in the creature, for regulating body temperature, This is why plenty of reptiles prefer a habitat having a warm climate. However, even in this habitat they are not active during cool nights, with the exception of crocodiles which hunt in water. In reptiles the blood flows at the temperature of the surroundings. When the whether turns very hot, they are forced to search for shelter from the hot rays of the sun. When the weather becomes cold, reptiles become sleepy. Because of a slowdown in the rate of breathing , their heartbeat also slows down and they are not able to move around with their normal speed. Cold blooded creatures are most active when the temperature of their blood is between 30 degrees to 35 degrees centigrade. Due to temperature changes they have a tendency to alternate spans of high activity with long rest periods. During active periods or when they are put in the sun, their temperatures rises. When the temperatures rises beyond tolerance, they go to rest in a shady place or go into water so that the temperature of their blood falls.