A recent question that came up was along the lines of, “Why do reptiles, such as crocodiles, like sun tanning?” As I explained, they aren’t actually sun tanning, they are basking. However, many people don’t understand why they do it.
Reptiles are cold-blooded. That is, they don’t have the means of internally regulating their body temperature. If their body temperature is low, they are sluggish. They don’t move quickly, don’t hunt, and if they have food in their stomachs, the digestion comes to nearly a standstill.
This presents a problem for the animals. They have a solution, though; basking. By laying in the sunshine, they allow the sun to warm them up. When they get to an optimal temperature, they can be active, can hunt and can digest the food they eat.
This true of reptiles that spend a great deal of time in the water, too. Animals like crocodiles, alligators, and turtles are often seen basking. Water can cool them down, so this lets them warm up. It isn’t just water reptiles that do this, though. Snakes and lizards to as well. In the early morning, it isn’t uncommon for rattlesnakes and sage lizards to bask on rocks.
Reptiles are so good at using sunshine to warm them up that they also use shade if they get too hot and need to cool down. The same rattlesnakes and sage lizards that were basking in the sunshine during the morning are often found laying in the shade of bushes during the heat of the day.
The animals actually have one advantage of using sunlight to control their body temperature. Warm-blooded animals like mice and people must eat a large amount of food, fairly continuously, because it is the digestion of the food that regulates their body temperature and produces heat, which they must maintain in order to survive. Cold-blooded animals don’t have this restriction since their body temperature is controlled externally. This is why a rattlesnake can go for over a week without eating after it has consumed a large rat. Some constrictors have been known to go well over a month without eating, after consuming a large meal.
There is a disadvantage, too. Reptiles have difficulty surviving in places that don’t warm up enough that they can have adequate temperatures for their bodies. Thus, there aren’t many snakes in northern Alaska or Canada, but there are quite a few in the southern US and Mexico.
Without basking, many reptiles wouldn’t be able to survive.