Alligators, although they are ectothermic and also equipped with a small brain, exhibit a surprising diversity in their responses to their environment and to each other. They are for more complex than mere animated logs or 12-foot-long eating machines. This group of pages show some of what I've been able to see in just two years (starting September of 2001) at Brazos Bend State Park.
This morning, not long after I'd started walking near Elm Lake, I heard
an alligator head slap near pier 2. As I started hurrying towards
the sound, I began hearing bellowing. When I got close to the source of
the bellowing, (it sounded like 2 females and one male) I noticed a large
male alligator swimming parallel to my course, That is, he was headed towards
the bellowing. I could just make out the male that had been bellowing,
when the larger one got close to it. The bellowing male was at least half
a length shorter than this male that followed me. The smaller alligator
beat a hasty retreat to the center of the channel...but only about 25 feet
or so away. The larger alligator showed a puffed-body/tail-arch posture
for a while, then got closer to the far shore and began bellowing (see
MY YARD, below or video clip
(1,452 kb)). When the large male bellowed, I'm sure I felt a subtle vibration;
similar to what one feels sitting next to a large, low frequency speaker.
As I looked at my video, it seemed to me that there is a slight vibration
of the camera near the "waterdance" stage of the bellow cycle.
MY YARD! I SAID, MY YARD! THERE THEY GO
The large male continued bellowing, and what sounded like two females (on either side of the large male) began bellowing as well. This went on for about 3 bouts. After the bellowing stopped, two smaller alligators (about 6 or 7 feet long) appeared from the East, swimming alongside each other. The large male turned, and swam out to meet them. The smaller one of the two stopped swimming immediately. However, the other one didn't, although it *did* try to swim around the big male. It was able to move around the large one, but the male continued advancing, and then turned to follow the small alligator (see I SAID, above or video clip (1,424kb)). And then the chase was on! (see THERE THEY GO, above or video clip (678 kb)) This chase, however, continued down Elm Lake for quite a distance; maybe 3 or 4 piers. Far enough to require binoculars to see them in the distance. That was a nice start to the day.
01, 2006 Earth Day Celebration at BBSP. I led a "gator hike" at Elm
Lake. We saw some great alligator behavior, and a territorial dispute.
Text below added 4/20/2006.
One of the reasons that I was so excited about seeing this social interaction (besides the fact that it happened in front of me) was that I had, not 10 minutes before, been lecturing to the hikers about various types of alligator social signals. Usually, when I lead the hike, I will stop near an alligator and-whether it's doing anything or not-I will lecture and demonstrate some aspect of alligator behavior. Sometimes, while I'm lecturing (interpreting), the alligator will do something, and if I haven't covered what the alligator is presently doing, I will try to put what it *is* doing into some behavioural context. By the way, this particular competition was probably driven by two factors. First, this is mating season, and alligators are territorial. Second, the water in the lakes in the park is VERY low. This means less area covered by water, and therefore a lot less available territory.
In this situation, I had just explained how alligators will often indicate social status by body position relative to the surface of the water. The nose slightly elevated (just the edge of the lips visible) is non-aggressive. Head flat with snout at water surface, is watchful. Submerging the head while holding it flat in the presence of another alligator is submissive. Back high in the water is dominant. Head with nose pointing up sharply can mean headslap or bellow--both highly dominant signals with the back submerged and the tail arched. Tail arched (center of tail elevated higher than the base and tip) can mean readiness to defend or what I consider a "query" regarding direction an interchange will take. These are all positions that the alligator will sometimes take while feeding, but then the body positions are in a different context. With no other alligators around these are not signals. All these images are from the short video clip I shot. The video clip can be seen here (wmv 26,372kb)
AFTER THE FIRST LUNGE SUBMISSIVE TRAPPED AGGRESSOR PASSES SUB
SUBMISSIVE STOPS AGGRESSOR IN FRONT
headslap is an action where the alligator lifts its head, then suddenly
drops lower jaw under the surface of the water, then slams upper jaw
to meet the lower jaw; resulting in a loud pop/slap sound--which is sometimes
accompanied by a short growl as the upper jaw is brought down.
I've seen this often immediately after a direct alligator challenge. I've
seen either the apparent winner or "loser" of the exchange (I assume
one that submits is the loser) do a headslap. Generally if the dominant
"winner" does it, the headslap is within view and within chase
of the "loser". Most alligator interaction is non-violent, and involves
a lot of submission and swimming away.
of many of these behaviors can be seen on my other pages, such as the "alligator
social signals" pages:
signals 01 social
signals 02 social
I learned a lot of this by watching the alligators use these signals and others in context over the last 4 years. An early source for comparision was a study available from the American Museum of Natural history, titled--"Social Signals of Adult American Alligators", by Leslie Garrick, Jeffrey Lang, and Harold Herzog (Bulletin of the American Museum of Natural History Vol. 160: Article 3; pages 157-192, 1978; click here to see the AMNH digital library and get the pdf.) This is a very small publication, like a small magazine in format, but it is a detailed study of alligator communication among animals observed in Florida. Another source for descriptions of alligator social signals is: Crocodilian Biology and Evolution, Gordon C. Grigg, ed. Feb, 2001. (pp. 383-408) There is also some reference in this book to the earlier work.
AGGRESSOR THRASHES TAIL SLOWLY TAIL ARCH WITH HIGH BACK SUBMISSIVE SUBMERGED TAIL ARCH
I'd talked about what I called the "panic dive". Although alligators can hold their breath for a long time (I've read between 1 and 4 hours), they cannot do this every time they submerge. If an alligator is surprised or under duress, it performs a "panic dive". In this circumstance, the alligator can only hold its breath for a short time, and generally resurfaces quickly to assess the situation that made it dive in the first place. I have often seen this in practice.
In the book Crocodiles:Inside Out, by K.C. Richardson, G.J. Webb and S.C. Manolis, there is a concise description of the circulatory changes that happen during what they term a "voluntary" dive on pages 81-82. According to the descriptions and the simplified drawings with them, crocodilians have two major connections in their circulatory systems which allow deoxygenated blood to mix with oxygenated blood. Remember--mammals have a 4-chambered heart, which keeps blood rich in oxygen seperated from deoxygenated blood, which allows for more efficient oxygen supply to the body and therefore more efficient metabolism. Most reptiles have a 3 chambered heart, generally less efficient because oxgenated and deoxygenated blood can mix together within the heart; resulting in overall less oxygen being available to body tissues. Alligators, however, have a four-chambered heart! However, there are to major connections in the alligator's circulatory system that allow for mixing of O2+ (oxygenated) and O2- (deoxygenated) blood. While this would seem to lessen efficiency--in fact might seem to be defects --these are part of a complex mechanism which allows crocodilians to remain under water for such long periods of time. As time passes while the
crocodilian is submerged, it can restrict the blood flow to its lungs (which aren't used then), skin, and other low-priority organs while simultaneously increasing flow to such high-priority organs as brain and heart; and it also deal with lactic acid buildup. When the crocodilian finally does surface after such a long period, it breathes normally; without stress incurred from its long period without air.
At the end of this description is a paragraph that states that during and "involuntary" or "fright" dive (which I called the "panic" dive") the crocodilian can only stay under for a short time. After this, it will resurface, breathe normally, and can then perform a "voluntary" dive and remain submerged for a much longer period of time.
Finally, I talked about a concept I call "escape in 3 dimensions". This is a concept I came up with myself, and I've been looking for various examples. Generally, I consider this a technique that is useful at the boundary between two environmental media. Examples are the boundary between air and water, air and ground, or ground and water. In the case of alligators, I've seen this during social interaction. As I understand it, most alligator communication requires water for transmission. A lot of information is conveyed by alligator body position relative to water surface. Water is also used for head slapping, bellowing (the low-frequency vibration--"water dance" over the back), tail swishing, and snout-bubbling (expelling air from nostrils or mouth to make bubbles). Alligators will occassionally interact on land, but such interactions often begin and/or end in the water.
Alligator chasing usually happens at the water's surface. The pursued and pursuer can move towards or away from each other. In all-out pursuit, speed can increase until both alligators seem like motorboats. Sometimes, a pursued alligator will raise its tail and thrash it enough to cause turbulance and splashing, then turn 90 degrees to the right or left. Sometimes this ploy works...briefly. The turbulance can disrupt the pursuer's visual and possible tactile sense (perhaps via ISOs) temporarily while the pursued alligator changes direction.
All of this is what I call "two dimensional" movement. The alligators are moving right, left, backwards, forwards--but all in one plane and still at the surface of the water. But, if the alligator can't escape, it may try in a *third* dimension---down, or up. The alligator may do the turbulance trick and submerge. When it submerges, it may do the 90 degree turn, or it may not. But, this is usually a panic dive, and the alligator usually can't stay submerged for long. When it resurfaces, the pursuer can locate it and continue the chase.
SHORT, STRAIGHT CHASE WHILE SUB DOVE AND TURNED AGGRESSOR CONTINUED... ...WHILE SUB SWAM UNDER
submerges, turns sharply, and swims below and at an angle-which allows
its pursuer to pass it-it may be out of visual range of the pursuer
it resurfaces. The alligator may also go "up" by leaving the water and
walking onto land. This ploy may work not because it becomes invisible
pursuing alligator, but because alligators are less comfortable on land
and the pursuer may not want to follow. The story I have on another
about the alligator with a mouthful of nutria being chased by another alligator
trying to steal it (and eventually others trying to take it) illustrates
of these movements. That alligator chase also shows a number of social
signals, my "escape in three dimensions--both onto land and under water",
and panic dives. You can see it on this page.
Before I shot this video, this aggressor ("dominant") had been cruising the water nearly an equal distance from both banks. My hiking group and I followed the patrolling alligator past 3 or 4 piers. One smaller alligator moved ahead of it, and eventually cruised to the far bank and kept a low profile. One alligator already at the bank slowly submerged as the aggressor passed by. Finally, the aggressor moved towards a 7-foot alligator that was resting with the front half of its body out of the water. The dominant slowed, and inched towards the beached alligator until it must have been floating over the tail. Suddenly, there was a flurry of motion as the beached alligator (which might have suddenly come awake) seemed to realize that the aggressor was so close and lunged onto the bank. The aggressor moved towards it again, and that's where the clip starts. If you watch the video clip from 04/01/06, you'll see the aggressor's side-to-side tail swish, indicating annoyance. The aggressor has his back high in the water, then turns back towards the alligator which had run onto the bank attempting to escape (it also didn't have much choice, since the aggressor was already on top of it when it was noticed). There's a sharp jump-turn into the water, and a panic dive. The submissive ("sub") surfaced off to my right (you an only see tail turbulance), which signalled its location to the aggressor, which chased it. The sub turned 90 degrees again (to my left), and did a shallow dive. Its escape route brought it right
to the bank in front of us. With a crowd of 20+ humans on the trail above, I didn't think it would retreat onto land, but I warned everyone to stand back anyway.
Here the submissive remained, waiting for the aggressor's next move. When the aggressor lunged forward again, the submissive did another panic dive, and went off to my right, bringing it behind the aggressor, and some distance away. *I* was confused, since I had been watching the aggressor's position relative to my group of visitors and was assessing this situation instead of just watching the alligators.
SUB TRAPPED AGAIN SUBMISSIVE ESCAPES... ...GOING UP, AND THEN...
...GOING UNDER AND TURNING SUB ANGLES BEHIND
Meanwhile, the aggressor--who had lost his quarry but didn't know it yet--stood with it's arched tail switching side-to-side, its back very high,
and its mouth gaping open. I've seen the alligator gape as a threat display--but open mouth by itself isn't necessarily a threat. It depends on
the context. An alligator sunning on a bank for a long time will sometimes open its mouth as a heat-regulation reflex. There's no tail thrashing, body
movement, etc. In this case the gape was obviously meant to intimidate. It worked on us, that's for sure!
SUB SWIMS OFF WHILE... ...CONFUSED BY TURBULANCE... ...AGGRESSOR SURFACES...
...WITH MOUTH AGAPE... ...BACK HIGH AND TAIL THRASHING
the water stopped moving around, the aggressor could see another alligator
in front of it. It went towards it, but that one wasn't
alligator that had made the aggressor so angry, and after a brief close
inspection, it left it alone (this is also interesting since it
that the aggressor wasn't attacking every other alligator, and could
therefore tell them apart.) Finally, after having driven
the other alligator, the aggessor moved a little further off (to the next
pier), and did a head slap. This was reported to me later by a
number of people who witnessed it.
This "escape in three dimensions" or "escape across a media boundary" is an exciting concept for me. I've seen some birds do something similar. A Coot and a Moorhen might get into an argument and start swimming after each other (left, right, forward, backward--one plane--2 dimensions). At a certain point, the target may start "fly-running" over the surface of the water, or just take off, or submerge (movement up or down, escape in another plane--3 dimensions). A squirrel will run here and there (one plane) if there is no tree, but once a tree appears, UP it goes. Rabbits may go down, if there is a burrow. One example that got me onto this line of thinking was the basilisk lizard. It can run well on land, but if pursued near a body of water, it can run across the surface for a while, before submerging and swimming away. What the lizard is actually doing is striking the water with outsplayed fringed toes hard enough to make a big "hole" in the water; and the then pulling its foot up out of the hole faster than the hole can close. This is made easier by the toes closing together which makes the foot much smaller as it's pulled up. While that foot is pulling up, the other is pushing down, and so on. A simple description of this can be found in the book, Extreme Science: Chasing the Ghost Bat--from the editors of Scientific American, pages 82-83. Or, you can look for the papers--"Size-Dependence of Water-Running Ability in Basilisk Lizards" by J.W. Glasheen and T.A. McMahon and/or "Running on water: Three-dimensional force generation by basilisk lizards" by S. Tonia Hsieh and George V. Lauder--for the technical data. There are a lot of complicated mechanical relationships at play here. Not only is the lizard using the surface of the water to run
on; but it's also keeping its balance and moving forward rapidly!
Anyway, this "three dimensional trans-medial movement" needn't just be used for escape. Some predators can attack successfully between media boundaries, surprising prey with an attack from an unexpected direction. A mouse can run in any direction horizontally, or burrow down...but it can still be surprised by an owl or hawk attacking from another medium (air) and third dimension (up). An osprey can cross the boundary between air and water and snatch food out from one medium (water) and bring it into another (air) with the fish being totally surprised. The ant lion pulls prey through the boundary of the ground from below. The prey is caught unawares by this attack from a third direction. The trapdoor spider also uses this third dimension to suprise prey expecting attack from everywhere but the medium it is walking on. And, of course, crocodilians can use this concept as well, and snatch prey through the boundary of air and water, or water and land.
© 2006 Richard Dashnau
If you'd like to know more about the park follow these links:
Brazos Bend State Park The main page.
Brazos Bend State Park Volunteer's Page The volunteer's main page.
Here are a few links to more information on alligators. There's a LOT of it out there.
Adam Britton's Pages 1
Adam Britton's Pages 2
Fish and Wildlife Page (Text)
Fish and Wildlife Endangered Species
Here are my "alligator behavior" pages:
|SOCIAL INTERACTION||CONFLICT AND CANNIBALISM||FEEDING||BABY ALLIGATORS||ALLIGATOR DENS||ALLIGATORS ON LAND||FOSSIL CROCS|
|SIGNALS 1||CONFLICT 1||FEEDING 1||BABIES 1||DENS 1||ON LAND 1||FOSSILS 1|
|SIGNALS 2||CONFLICT 2||FEEDING 2||BABIES 2||ON LAND 2|
|SIGNALS 3||CONFLICT 3||FEEDING 3||BABIES 3||ON LAND 3|
|SIGNALS 4||FEEDING 4||BABIES 4||ON LAND 4|
|SIGNALS 5||FEEDING 5||BABIES 5||ON LAND 5|
|SIGNALS 6||FEEDING 6||BABIES 6||ON LAND 6|
|SIGNALS 7||ON LAND 7|
And, this page shows alligators at the park, on land, near various landmarks at the park.
Go back to my main alligator page, Alligators
Go back to my home page, Welcome
Go back to the See the World page.