Desert spring is in the air. Bird and insect sounds are louder. Plants are showing off their new tender spring green growth, and each morning, there is definitely a soothing warmth chasing the night chill away. Yet in the desert, there is one tell tale sign that signals the coming of spring more than any other... the appearance of reptiles. These cold-blooded creatures have been hibernating through the cooler months and a series of warm days will cause them to begin to stir. It's their time.
The first reptiles to appear are the small lizards. Due to their size, their body temperature warms and cools more rapidly, so they can warm up and get moving easier than the big guys. This week, we noticed a marked increase in small lizards lounging on the sun-warmed rocks who skitter away at the slightest intrusion.
Hibernation is one of those perplexing design mysteries found in the natural world. Why do some creatures have the ability to slip into an efficient energy saving mode for several months when others have to store food caches, migrate or find some other crafty way to tough it out when food supplies dwindle?
In the case of lizards and other "cold-blooded" or ectothermic* creatures, their bodies are dependent on the outside temperature to regulate internal temperature and fuel their metabolism. Instead of getting most of their energy from the food they eat like mammals do, cold blooded animals are energized by the warmth of the sun. Their muscles are triggered by a chemical reaction that is fast in warm weather and slower in cold weather. Cold blooded, or ectothermic animals are usually elongated or flat in design, allowing heat to be exchanged with the surrounding environment more efficiently.
The chemical process design in ectothermic animals is fascinating. At the cellular level, water around each cell can freeze, but due to a flow of glucose into the cell, the fluid inside the cell does not freeze, almost like it has been injected with a natural anti-freeze! Animals like frogs can hibernate at temperatures below freezing and still survive.
The next time you see a lizard lounging in the sun, remember that this well-designed creature is not interested in sporting a tan, but rather in getting an energy boost! Observe his sleek elongated body which can be quickly warmed through by the heat of the rock underneath and the sun overhead. Brilliant design!
Ectothermic - Of or relating to an organism that regulates its body temperature largely by exchanging heat with its surrounding environment. dictionary.com
References and Resources
Arizona-Sonora Museum - Diurnal or Nocturnal Hide and Seek
BBC Nature Wildlife - Hibernation
American Chemical Society - How Animals Survive Temperature Extremes
Image: Sharon Pegany
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