Sometimes the tiniest differences in appearance turn out to be much more important to animals than we could ever imagine. For example, how could pimple-sized bumps on a water-dwelling alligator’s face affect his ability to survive?

Throughout the 220 million years of crocodilian development those without bumps on their upper and lower jaws lived on land, while those with the tiny nodules on their jaws lived in water. This difference was not fully examined or explained until 2001. During a field trip to collect alligators for use as live study specimens University of Maryland neuroscientist and doctoral candidate Daphne Soares noticed the bumps on the reptiles captured in the Louisiana swamps and began to wonder about their purpose.

In the May 2003 issue of Smithsonian magazine science writer David Berreby reported the story of her discovery of the purpose of those bumps. Valentine Lance of the Center for the Reproduction of Endangered Species in San Diego, California called the results of her research a “major breakthrough in crocodilian sensory physiology.” So exactly what was the breakthrough? Why marine crocodilians have bumps?

They’re “pressure receptors” that allow crocodilians to locate prey underwater. Even when deprived of both sight and hearing the crocodilians can use that additional sense to move to the location where a possible victim caused a ripple on the surface of the water.

With that same spirit of intellectual curiosity, in 2005 I chose the Palo Verde Estuary as the site for my University of Colima thesis research on the Crocodylus acutus. I conducted the first full-scale study of these reptiles living in the estuary.

The American crocodile has the second widest distribution of all the New World crocodlians. Our local species is also found in Belize, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, El Salvador, Guatemala, Haiti, Honduras, Jamaica, Nicaragua, Panama, Peru, the United States, and Venezuela.

It is an endangered reptile partially because of over-hunting and loss of habitat. Its hide is the softest and most pliable of all species which makes it more commercially desirable than others. And human encroachment into the traditional breeding grounds disturbs their ability to reproduce and destroys nesting places.

Three of the 23 surviving species of the family Crocodylia are indigenous to Mexico. The acutus, also known as the American crocodile is also identified as the River crocodile even though it is usually found in bays, estuaries, mangrove swamps, and lagoons. On the Pacific Coast of Mexico it can be found from the area of the Suchiate River of Chiapas State on northward to the Fuerte River region in Sinaloa State north of Los Mochis. Following the routes of various rivers it can sometimes be seen over 100 kilometers inland. The approximately 69 living in the Palo Verde Estuary were introduced via the Armeria River.

Crocodylus acutus is the largest Mexican crocodile and can grow to 7 meters; well over 20 feet long, but usually it doesn’t exceed 12 to 13 feet. Another Mexican crocodile, Crocodylus moreletii, or Swamp crocodile is generally found farther south, from the Yucatan on into Central America.

The third and smallest species, usually less than 7 feet long, Caiman crocodilus chiapasius, or Caiman seems to have the best public relations department of all the Crocodylia. Perhaps it sounds more exotic, but for whatever reason, many mislabel all crocodiles in Mexico as Caimans. As you might guess from his scientific name, you’ll find him living in the rivers and still waters of Chiapas State.

Acutus differs in appearance from all other New World crocodiles. First, he has a wart, or bump in front of each eye. His skin is much smoother, and his dorsal scales are arranged randomly rather than in neat rows.

Crocodylus acutus is a voracious carnivore. As a youngster he feeds mainly on aquatic insects, and small fish and amphibians. As an adult, the diet expands to include birds, small mammals, turtles, and young crocodiles. That’s one of the reasons why in spite of the prolific rate of egg production the estuary is not overpopulated with crocodiles. For a number of reasons, only about 10% of baby crocodiles survive to adulthood.

In addition to being voracious, the crocodile is a deadly predator. He can smell flesh for up to four miles, and using his sensory ability to isolate movement at the surface of a body of water he can submerge and approach his prey undetected.

He is well-suited to sub-marine attack. For ease of surface observation his eyes, ears, and nostrils are all located on top of his head. He has a fold of skin in his windpipe that he can close to allow him to open his mouth underwater while breathing through his nose. His ears are also protected by a skin flap when submerged, and an opaque third eyelid provides protection when below the surface. His pupils are narrow vertical openings which enhance low-light vision.

His effective striking range is 10 feet so he doesn’t need to be close in to be dangerous.

And just as the sea turtles, the three species of Mexican crocodiles are all protected by federal legislation. The ancestors of these misunderstood reptiles survived the catastrophe that destroyed the dinosaurs so perhaps we can help them survive modern civilization.

My studies have answered a number of questions about the River crocodile but many are yet to be asked. With your support I’ll be able to continue research to benefit both the crocodiles as well as the entire ecosystem.

For more information please e-mail Dr. Rivea at tortugacuyutlan@hotmail.com

Don Adams can be reached at dondelmundo@yahoo.com