Ask Old Pete

 

These are some questions submitted by students involved in the education program. These answers were generously provided by Peter Braziatis. Thank you, Peter!

How do alligators close their ears, nose, and throat to swim underwater?
Alligators also have a “third eyelid” like all crocodilians have a “third eyelid” which is really a transparent membrane properly called a nictitating membrane. While they have the same kind of eyelids as we do: an upper eyelid that closes from the top down, and a lower eyelid that closes from the bottom up, the third eyelid moves to cover the eye from the front to the back automatically when the animal submerges, and acts like the see-through glass of a diver’s mask. While the animal can’t see clearly through the opaque membrane, it can see dark and light and protects the eye itself from damage by sticks and other things while the animal swims under water.

While alligators have a leathery flap of skin over the ear openings on the side of the head, which protects them from damage, it doesn’t actually keep out water because the flap is an open slit towards the rear. The actual ear canal is covered over by the tympanum- a tough membrane that acts as the ear drum. This membrane vibrates as ours does in response to sound waves, and probably water born vibrations as well. So if you lift up the flap and look into the ear you will see what looks like a white piece of tissue paper that stretches across the inner ear canal.

The nostril openings are two slits that act like shut off valves at the top of the nose, and clamp shut in a tight seam, to close out the water when the animal submerges. We do the same thing when we clamp our nose shut with our fingers when we want to hold our breath. The only difference is that alligators do it with built in muscles that surround the nostril openings.

Alligators have a cartilaginous flap of tissue at the back of the tongue that perfectly fits the inside shape of the throat. It fits so well that the alligator can open its mouth to catch and crush food underwater without letting water into its throat or lungs, but to swallow the food the alligator has to raise its head out of the water to let the food slide past the throat valve to get into the esophagus leading to its stomach. The valve flap has another use. It helps the alligator bellow by regulating the volume of air being expelled by the alligator when it exhales as it roars.

How many teeth does an alligator have at one time?
Usually 36 - 40 teeth on the upper jaw and 38 - 40 on the lower jaw.

Do alligators carry salmonella like lizards do?
People get salmonella from lizards, turtles and possible alligators and just about any other animal you can think of. The problem is not really the animal.

Studies have shown that turtles that live in natural environments that are not polluted with fecal materials from cattle, pigs, etc.- rarely carry salmonella. The turtles that are found to carry salmonella usually live in polluted cattle ponds in pastures, sewage drainages, and places like that. People usually contract salmonella from pet turtles that live in aquariums that are contaminated with decaying food left over after the turtle eats and the tank is not cleaned afterwards for days. Children who touch turtles covered with contaminated water from their tank, and then put their hands in their mouths afterwards get the disease. Most people who get it from their pet iguana when they let the iguana run loose in their house, and it defecates on the table where food is served.

In zoos where keepers take care of many different animals like monkeys and other animals that can carry disease, they rarely get salmonella or other diseases like that, because they are required to wash their hands with hot water and soap each time they touch an animal or its living quarters, and never, never put their hands in their mouth or eat without washing or even showering. We found that keepers that smoked were most apt to get diseases from animal feces because while smoking they put the cigarette to their mouths with their dirty fingers over and over again, and transmitted bacteria or virus directly into their own mouth along with the cigarette.

Is it true that a female alligator will only mate with a male who can dunk her?
Well, not exactly. Female crocodilians, including alligators, will reject or even kill males that attempt to mate with them if they are smaller than the female. Small males usually do not get the opportunity to try in the wild because the largest males dominate the scene, drive off smaller males from the territory, and get to select the females.

Its mostly in captivity that the problem occurs, when a farmer tries to get a not-so-big male he selects to breed with a large female alligator, and she will have none of the puny fellow. Females are smaller than males as adults, and never reach the size males do to begin with. A male has to be much larger than a female in order to perform the breeding act. During copulation, the male climbs onto the back of the female with his head directly behind the base of her head, his front legs grasping her body behind her front legs. Then his body must extend down the length of her torso and wrap his tail down and around and across under her body, so their vents align for penetration. He has to be longer than she in order to reach that far. It then follows that the larger he is, the heavier he is, and so weighs more than the female does. Thus, when he climbs on her back to assume the mating posture- dunk 1- at least, because he is so heavy and they are suspended in water. He often mounts several times as she swims- dunks 2, 3, 4, 5, etc.

Does he have to dunk her three times to be acceptable? No- but to breed successfully and accomplish intromission, he has to be larger, longer, and that means heavier than she is, to mount properly, and out compete other males to begin with.

What happens when alligators are turned upside down and pass out?
It is not really "passing out" as the animal is capable of outside stimulation. Temporarily dazed and disconnected would be a better way to think of it.

It appears to be much like what a human experiences when we suffer a bout of vertigo. A disconnect occurs between the vestibula aparatus of the inner ear and the brain. Tiny calacrous otoliths, within tiny sacks that are lined with sensory hairs within the inner ear, tell the brain which way we are oriented, which side is right side up and which is wrong side down. When some people put their head down, or rise from a lower head position abruptly, the otoliths may move and stimulate the sensory hairs in a way that causes the brain to be disoriented, and lose our perception of up and down. We experience dizziness and an inability to control our movements. The effect is short duration, and studies recommend that shaking the head again, in a particular motion, may cause the otoliths to move, enabling us to again receive normal signals from the inner ear.

Alligators' ears are not exactly built the way human ears are, but they still rely on the inner ear to tell them up from down. Lobsters use sand in the inner ear, held in place by normal gravity, to tell them that they are right side up. When researchers replace the sand with iron fillings, they can use a magnet held near the lobster's head to move the filings inside the ear and fool the lobster into flipping upside down, thinking it is right side up!

As for the added benefit of rubbing the alligator's belly to induce the animal to remain motionless, once it is on its back, we really don't know. In any case, second physical touch seems to give the animal a sensory signal that helps it reorient, and the animal immediately turns back over and becomes wide awake.

Under normal circumstances, crocodilians never lay on their back on land or in the water. They may roll and turn upside down momentarily to dismember prey, and when they are in combat, but crocodilians never remain belly up on their back by choice. Old alligator wrestlers know full well that the trick is not "putting the 'gator to sleep" after the animal is forced onto its back, but in getting the animal forced onto its back to begin with.