ALLIGATORS

 

The largest reptiles at our Refuge are native alligators. They are in the order of reptiles called the Crocodilia. The Spanish call both alligators and lizards lagartos but the common name alligator comes from a misspelling and mispronunciation of el lagarto --> al lagarto --> alligator.

 

 

Baby sitting on mother alligator - Tom Rasmussen

 

Like all reptiles alligators have scales. The surface scales along the back, called scutes, are each underlain by a bone between the skin and the underlying skeleton. These bones are called osteoderms. The osteoderms are comparable to our kneecap bone (patella) that lies between the skin on our knee and the underlying leg bones.

 

 

Osteoderm from about an eight-foot alligator.

 

The belly skin lacks scutes and osteoderms and is favored to make leather for belts, bags, and shoes.

 

 

Alligator mississippiensis, the American alligator

 

Alligators and Crocodiles

 

We only have American alligators at our Loxahatchee Refuge. American crocodiles occur in brackish and salt water from Biscayne Bay south into Florida Bay. They do occur together in our southern Everglades. Do you know how to tell them apart?

 

 

 




Alligator or crocodile skull?

 

 




Alligator or crocodile skull?




 

Perhaps this image of the heads of live animals will help you decide which skull is which. Look at the teeth and at the head relative length and width.

 

 

 

Crocodiles and alligators are similar in many ways. They both have scutes. They can be very active since they have an efficient four-chambered heart and an efficient lung. They both are mostly aquatic but can lunge out of the water and run quickly for short distances on land. They both have a huge tail that is the main means of swimming. And they both have lots of replaceable sharp teeth that break off when they clamp down and thrash and twist about to tear prey into pieces.

 

Ogden Nash has a fun poem that suggests that scientists may be the only ones who can reliably tell crocodiles from alligators.

 

The Purist

 

I give you now Professor Twist,

a conscientious scientist.

His trustees exclaimed he never bungles,

and sent him off to distant jungles.

Camped by a tropic riverside,

he chanced to miss his blushing bride.

She had, his guides informed him later, been eaten by an alligator.

Professor Twist could not but smile,

you mean, he said, a crocodile.

 

Nash is pretty accurate in his poem. Alligators do not occur in the tropics. And old-world crocodiles in the tropics are very dangerous. Both are top predators in their communities.

 

 

 

Cooter turtle and alligator

 

Should the cooter turtle be afraid of the big bad alligator? Actually the turtle need not worry because the alligator is basking and/or sleeping. When the alligator slides into the water, all the animals know it is now in hunting mode. They suddenly move out of the water or swim away quickly. They make loud noises to warn other animals. And many, like these moor hens, escape.

 

 

 

 

 

 

Sometimes birds do not escape. An alligator has caught a coot.

Barry Schein

 

Myths and Misconceptions about Alligators

 

Our American alligators are really not very dangerous when you realize that in the past 60 years they have attacked humans 356 times with only 25 fatalities. The per person rate of attack has declined dramatically in the past 20 years. This risk is low compared to driving to the grocery store.

 

Douglas Florian writes:

 

The crocodile's smile is wide

enough to stuff a pig inside.

But did you know that alligators

sometimes swallow second graders?

 

NOT REALLY! Alligators are dangerous to us only under two conditions.

 

The first condition is if we feed them and they come to associate humans with food. At our Refuge people fishing inadvertently feed alligators so it is not wise to wade by the fishing pier. I once saw an angler catch a big bass and have a big alligator grab it. The angler unwisely tried to pull the bass from the alligator's jaws but it suddenly swam away and pulled the angler into the canal! The biggest alligator I have seen by the fishing pier is the one folks call one-eyed Pete. Perhaps Pete finds it easier to steal fish from anglers than to catch fish on his own.

 

Tongue-in-cheek sign about alligators: "NO SWIMMING! Tourists tend to give our alligators indigestion." Serious sign on federal land: "Feeding, enticing, or molesting alligators prohibited. 372.687 F.S. Up to $500.00 fine."

 

The second dangerous condition is a mother with babies. Mother alligators help young hatchlings emerge from nests of rotting vegetation and guard them for a year or two. If young make squeaking sounds, the mother arrives immediately and will aggressively attack anything that threatens her young.

 

 

Photo contest winner 2009 Florida State Parks

 

 

 

 

Chuckle at this Gary Larson cartoon.

 

Alligators are ecto-therms that means they bask in the sun to warm their body temperature. We humans are endo-therms that means we produce our heat internally. When alligators have warmed in the sun to a human body temperature of 37C (98.6F), they can be active and hunt. In summer water temperature can be as high as 32C (90F) and alligators need only bask early in the morning or in the late afternoon before they hunt.

 

 

 

Can you tell what is wrong with the University of Florida mascot? The problems are with body proportion, stance, front feet, and nature of eyes, teeth, and mouth.

 

 

University of Florida mascot

 

The University of Florida mascot is inaccurate in many ways:

1.    relatively small tail,

2.    upright stance,

3.    grasping front feet,

4.    mouth opening at the back,

5.    teeth too large and too few,

6.    eye should be round and pupil centered with no mean look

7.    and habitat for the football team, "The Swamp", is wrong. Swamps are forested wetlands; alligators live in grassy wetlands called marshes.

 

 

Alligators are no longer an endangered species

 

Currently, in the dry season alligators can be very dense in our canal and in pools in the Everglades so it is hard to imagine that they were once very rare.

 

 

An unusually dense concentration of alligators along a canal in a very dry season

 

As recounted in Gladesmen in early days folks trapped and sold alligator hides for a living. They caused the alligator to almost go extinct. When Everglades National Park was established, poachers still hunted alligators. But when the alligator was listed as an endangered species under the Endangered Species Act, it made a dramatic recovery. Now people can get licenses to hunt and to farm alligators for meat and hides. The alligator is no longer endangered.

 

 

Drainage and canals decrease the positive effect of alligators on biodiversity in the Everglades

 

In the Everglades and other large wetlands, alligators are known as a keystone species. Laura Brandt, a former Senior Biologist at our Refuge, explains that the holes alligators make provide the deepest and highest microhabitats in marshes. As a result they greatly increase both plant and animal diversity. In the dry season the holes remain wet and so are refuges for alligators, their prey, and other wildlife. Alligator holes have species found nowhere else in the marsh. And the edges of alligator holes have species of plants otherwise only found on elevated tree islands. Because the holes alligators dig provide habitats for so many species, the alligators are called a keystone species.

 

 

Alligator hole with zonation of plants in and around it

 

An alligator creates a hole as it thrashes its huge tail to push mud to the periphery of the hole and grabs plants and carries them to the periphery. The hole may become up to three meters deeper and the edge as much as one meter higher than the surrounding marsh.

 

In a recent report Brandt, Campbell, and Mazzotti document how canals and levees have decreased the frequency and distribution of alligator holes in Water Conservation Area 3A. Compared to the marsh center, their map shows that the driest area to the north has many holes and the areas near canals have few holes. This is because, as the dry season progresses, large alligators are attracted to deep water in canals. So they make fewer alligator holes.

 

In another part of their study the authors document that larger alligators are most frequent along canals and both hatchlings and small juveniles survive poorly along canals. Deep water in canals have big fish for large alligators to eat but little shallow water with small, fish, shrimp, and insects for small alligators to eat. And the big alligators eat little alligators.

 

Along Canals

  • no alligator holes
  • many large & few small fish
  • many big & few small alligators
  • few numbers & kinds of birds
  • just deep water
  • shore only dense cattails

Marsh Interior

  • many alligator holes
  • all sizes of fish
  • all sizes of alligators
  • high bird diversity
  • all water depths
  • high plant diversity

 

Peripheral canals encircling the Refuge and other Water Conservation Areas, have a low diversity of both plants and animals. In addition to uniformly deep water, high plant nutrients from urban areas and Agricultural areas are a problem. The aerial photo here shows the sharp gradient from mostly tall and dense cattail and willow by the canal to a diversity of species and patchy open water in the marsh interior. This gradient is due to decreasing nutrient concentrations.

 

 

Aerial of canal, trails, & marsh interior - Jake Paredes

 

Is alligator bellowing only a lot of bull? Yes? No?

 

 

As an alligator bellows, its body vibrates and water drops dance

 

 

If you voted that only bull alligators bellow, you are wrong. Both males and females bellow to attract mates and defend territories. Females only grow to about 10 feet long. Males grow up to 18 feet long and so sound a lot louder. And, for reasons we do not understand, there are often more adult females than males in a population and so most bellowing we hear is by females.

 

Here are two excellent links to videos about alligators. The first by Seminole Chief Jim Billie has an excellent sequence of Billie's two year old catching a complaining baby alligator and getting bitten. It also has great footage of how an alligator rolls and twists when caught or when eating prey. At the end of the second video by Mark Renz are excellent pictures of alligators bellowing.

 

http://www.youtube.com/watch?v=jDl4U9ZiZzk&feature=related

 

http://www.youtube.com/watch?v=A7BynOp8_M4

 

 

REVIEW QUESTIONS

1. Alligators are very dangerous to humans.

2. The alligator is called a keystone species because its activities increase the local species diversity of plants and animals.

3. The alligator is an endangered species.

4. Only male alligators bellow.