American Alligator at Circle B Bar Reserve in Florida.

Meet the Amazing Alligator



Introduction  |  Taxonomy, Phylogeny & Etymology  |  Distribution & Population  |  Ecology

 Anatomy & Physiology  |  Diet & Digestion  |  Thermoregulation  |  Reproduction  |  Neonate Care  |  Ethology

Survival  |  Human Conflict  |  Cultural & Commercial Impact  |  Conservation


Prime Observation Locations  |  Bibliography  |  Filmography  |  Suggested Publications  |  References



An alli gator afloat in water reflecting the gold of a sunset.AMERICAN ALLIGATOR

Alligator mississippiensis


Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Superorder: Crocodylomorpha

Order: Crocodilia

Family: Alligatoridae

Genus: Alligator


(Image: © istockphoto/LarryLynch)



7. Thermoregulation (Body Temperature Control)


Unlike a mammal or bird, reptiles are ectothermic, specifically, poikilothermic- as it must absorb warmth from outside sources (ground, water), ultimately from the sun, because its temperature varies according to its environment; this behavior of maintaining warmth is known as thermoregulation. The alligator lives every day monitoring the environmental temperature gradient, slipping onto warm spots of land, then perhaps back into shade or the water to cool off. It must maintain a safe temperature in order to keep a healthy metabolism - good for the organs and digestion. Reptilian behavioral repsonse to cold weather is called brumation (referred to by some as hibernation), and to warm weather, estivation.


SOLAR BASKING. Understanding the daily routine of a reptile requires attention to temperature, one of its principal, constant concerns in the daytime since it is only then that I can take advantage of the sun's rays by basking exposed to them, or to elements that have been heated by them (such as water or ground). The animal studies its resources, light, shade and water, and makes choices from one occasion to the next, relative to other conditions around it (threats, prey availability, etc.). While most thermoregulatory behavior may involve basking on dry land. a partially submerged crocodilian's body can process heat especially among the upper part that is exposed to the warm air by increasing blood supply there rather than to the submerged portion, an impressive variant of efficient thermoregulation. (Where alligators are kept by humans in warm natural springs, the 'gators will have to exit the water for a period of they feel too warm, even if there is snow on the ground!)


'SOLAR CELLS'. The arrangement of bony plates on the crocodilian's dorsal surface are called osteoderms (literally translated, "bone skin") or, colloquially, scutes. In addition to serving as armor - rigid reinforcement of the top of the body - they also serve as "solar cells". The bony plates are porous to facilitate blood flow to the surface; the blood is warmed by the sun's rays just under the thin layer of dark hide above the bone, and circulates back into the body. This animal may have evolved a dark coloration in order to absorb more heat to survive in the cooler, temperate zone it inhabits.

The bony back of an alligator.

The alligator enjoys from its back the power of a "solar panel", comprised of individual "cells" in the form of bony plates called osteoderms. In addition to serving as ultra-tough armor on the dorsal surface, these units absorb heat and convey it into the alligator's bloodstream.



An alligator osteoderm.This image shows an osteoderm with its pores and reinforcing ridges. The specimen shown is from a massive bull alligator that measured more than 13ft/ 4m in length; a penny coin shows scale.


GAPING. On a similar note, scientists don’t know for sure why animals – including Homo sapiens and reptiles - yawn, but it may be for one or more of the following reasons: To “stretch”, that is, to flex muscles and joints that have become too stiff, and thus to increase blood pressure and heart rate. Another reason, fitting for a reptile, is that it is an act of thermoregulation, exchanging air with its environment, similar to the panting of a dog. The gaping behavior is often understood by non-experts as a show of aggression but might merely be considered a prolonged yawn.


FEVER INDUCTION. Studies have demonstrated that the alligator, when suffering from an infection or inflammation, can instinctively induce a fever by self-determined, maximized or prolonged exposure to heat by the solar basking behavior. The fever, of course, is meant to to help the body fight the malady by increasing stress on the host bacteria. This behavior deepens our understanding of this very crucial abilty of the animal to regulate its body temperature in a situation that challenges its survival. (This behavior was also discovered in lizards and turtles.)


FREEZING CONDITIONS. Under freezing conditions, its "icing response" includes lying in torpor in the frozen water, bringing its heart rate down to a few beats per minute or fewer, compared to an average of 31 in a normal, minimally-stimulated alligator. (If you'd like to read in more depth on this particular subject and view a striking photograph of an alligator in extreme brumation, you may enjoy this article.) The alligator, under such a dangerous and extreme condition, will lie in the water at the gradient of  the water bank for bodily support, and hold its head to the water's surface, allowing ice to form around its protruding nostrils, which are located at the tip of the snout; the alligator, in torpor (a kind of 'suspended animation"), will breathe thorugh this hole until the ice melts - provided it melts in time for the animal to recover. Alligators may survive freezing termperatures, but only for a limited time. One study showed that two large alligators could not survive in temperatures lower than 39-41°F/ 4-5°C.


As mentioned in the section herein, "Anatomy & Physiology", the alligator cardiovascular system can divert carbon dioxide-rich blood to the stomach to increase the efficiency of digestion after an alligator has swallowed a meal.  


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