Raun B. Shephard
Animal Life, NSC 1307
Spring 2002
Article Review
"Everything You Need To Know about Surival You Can
Learn From an Alligator"
By Jack McClintock
Introduction
The article I have chosen to review is "Everything You Need To Know about
Surival You Can Learn From an Alligator" ," which appears in the May 2001
issue of DISCOVER magazine, Volume 22, Number 5. This was an interesting
article that explored the inherent characteristics of American alligators
(Alligator mississippiensis) that have allowed them to survive over 200 million
years.
The American alligator is listed by the federal government as a species of
concern due to their likeness in appearance to its endangered counterpart,
the American crocodile. The American alligator is in the Subclass Diapsida,
Superorder Archosauria, Order Crocodilia, Family Alligatoridae, Genus Alligator,
Species Alligator mississippiensis.
The American alligator is found in in the Southeastern United States, including
Alabama, Arkansas, North & South Carolina, Florida, Georgia, Louisiana,
Mississippi, Oklahoma, and Texas. Some of the larger population may be found
in Florida and the coastal regions of Louisiana and Georgia. Alligators are
not too tolerant of salt water; they prefer fresh water. During the summer
time, they may sometimes be found lounging in people’s swimming pools.
The American alligator varies in size depending on sex: females usually reach
lengths just under 9.8 feet, while males have been reported to have reached
sizes up to 19.8 feet. Both sexes have bodies that are elongated, bearing
bony plates that give the alligator an armored appearance. They also have
four short legs with five toes on their front feet and four on their rear
feet. The adult alligator is usually olive brown and black with a pale underbelly,
whereas the young have bright yellow stripes against a black background.
While alligators are often confused for crocodiles, there is a way to differentiate
them. In alligators, when their mouth is closed, the lower teeth fit into
some natural depressions present in their upper jaw. Crocodiles, on the other
hand, have teeth that are not hidden; their teeth may be seen on the outside
of the upper jaw. Crocodiles are also more aggressive than alligators.
An interesting fact is that, during cold spells, alligators do not eat. As
their body temperature drops, their metabolism drops; so, they don’t need
that much food. Surviving in freezing conditions requires that alligators
place their bodies underwater and keep their nostrils above water, allowing
them to breathe while their body is trapped in the ice; this process is called
the "icing response."
An interesting fact is that alligators at any point may have 74 to 80 teeth.
Over time, an adult alligator may go through 3,000 teeth.
Article Summary
Those involved in the study of the American alligator included Walt Rhodes,
an alligator project supervisor for the South Carolina Department of Natural
Resources; his research partner, Jeffrey Lang, a biology professor at the
University of North Dakota; and Lisa Davis, a graduate student. Zoology professor
Louis Guillette of the University of Florida commented on the alligators
reaction to toxins and its relevance for humans. Perran Ross of the Crocodile
Specialist Group at the Florida Museum of Natural History added perspective
to the connection to the alligators aquatic environment and their survival.
Rhodes and Lang took blood samples in order to help them identify alligators
by their DNA, helping them keep up with kinship relations. Davis, the graduate
student, decided to use DNA to establish which alligator was the father and
which mother laid the eggs, so that they could determine how often females
nested and whether or not it is common for clutches to have two or three
fathers.
Researchers have wondered why the alligators were able to exist before dinosaurs,
with dinosaurs, and still exist after dinosaurs. They also wondered about
the implications any discovery could have toward any prospects of long-term
survival for humans. Their studies were based around the adaptability of
the alligator. Lang and Rhodes realized that adaptability has to be studied
over the long-term, specifically because of the necessity of a specie to
have both males and females to mate.
In this article, McClintock explains the habitation that covers and protects
alligator eggs - a nest made of cord grass that's three feet high. In taking
the eggs from the nest and sexing them after they hatch, Lang and Rhodes
found that the sex ratios inalligators may vary widely, depending on the
weather. It was reported that cold or extremely hot temperatures produced
females, while intermediate temperatures favored the production of males.
They discovered that temperatures may vary within a enough to produce males
in the center and females around the edges.
McClintock reported that temperature not only determined the sex of alligators
but affected their body temperatures, emphasizing that alligators, cold-blooded
animals, may adjust their body temperatures. This, in turn, would change
the amount of food they would need to eat and metabolize to grow. Lang made
comments on the effects of an alligator warming up, whereas the article mentions
that an alligator may also just lay around, not eat, and still survive.
Rhodes pointed out yet another example where temperature affects alligators.
If temperatures are excessively high, the embryos could develop a twisted
tail and a large bulb-shaped cranium, what Rhodes calls 'helmet head.' At
a later time, Lang found out that temperatures that are extreme also affect
the growth rate and behavior of alligators. He found that low temperatures
produce tougher animals. Higher temperatures produce a fast grower, which,
if male, would 'have a breeding advantage.'
In addition to the myriad of effects that temperature has on alligators,
zoologist Louis Guillete acknowledged the effects that environmental toxins
have on the American alligator. In the early 1990s, he discovered that certain
synthetic chemicals can act like estrogen that could feminize a male-producing
egg, if they even touched the shell. The male would not be able to reproduce,
due to a low testosterone count.
While the researchers had data to back up their empirical observations, there
was still an area where scientists had to theorize - factors that contributed
to the alligators survival where the dinosaur failed. There were two factors
considered the cold-blooded nature of alligators and their ability to survive
in an aquatic environment. Theorists proposed that dinosaurs may have been
animals stuck between being cold-blooded and warm-blooded that lived on land.
They proposed that aquatic environments softened the effects of whatever
pressed dinosaurs into extinction. That, they propose, is the reason alligators
still survive - ability to survive in aquatic environments, living off of
little food.
Comments
Jack McClintock did an excellent job of presenting information about the
American alligator, a most amazing creature. Existing before, with, and after
the dinosaur establishes the alligator as a true wonder of nature and a real
survivor. I didn’t even know alligators had been around that long.
I was fascinated to find out about the alligators temperature-determined
sex. It seemed that so much about the alligator revolved around temperature,
determining their sex and effecting their activity level, body temperature,
metabolism, and feeding habits. I was also impressed to read that the method
Walt Rhodes invented was one that was used worldwide, sparing the lives of
countless alligators, who would have been killed otherwise.
I thought it was interesting that the sex ratios could vary so much between
years. McClintock mentioned that some nests could have all females, all males,
or some of each. That helped me understand why Lang and Rhodes would have
to approach the study of alligators reproduction ability over the long-term
as it relates to their ability to survive.
I wondered if monitoring alligator sex ratios would really benefit human
nature. On one hand, I would hope that alligators sensitivity to certain
chemicals would alert us to their presence in the environment. Yet, I also
wonder if the findings would be significant enough to justify researching
alligators and the impact the environment has on them.
Bibliography
Jack McClintock; "Everything You Need To Know About Survival You Can Learn
From an Alligator;"
DISCOVER, May 2001; Volume 22, Number 5
Crocodilian Species List
http://www.flmnh.ufl.edu/natsci/herpetology/brittoncrocs/csp_amis.htm
The University of Florida Institute of Food and Agricultural Sciences: AgriGator
Alligators
http://agrigator.ifas.ufl.edu/gators/