Alligators alter their environment in various ways. They can make "gator holes", or "burrows" (which are sometimes called "dens".) During my time at the park 
(more than 16 years), I've been able to see some of these structures. While there are many references to alligator burrows, or dens, I can find little information on
the actual shape and size of them. I've found some information in the book "Life Traces of the Georgia Coast ", by Anthony J. Martin PhD, and his companion 
website of the same name. 
The alligators make their structures to alter the environment to their advantage. Gator burrows can serve as shelter from extremes in temperature (both hot and
cold); as a receptacle for water (it can maintain some moisture within); and even as a temporary shelter from fire. An alligator den is usually excavated under the
water. It goes straight for about a meter (3.28 ft), then can turn right or left. The burrow continues until an end chamber - sometimes above the water table, 
sometimes not - that is wide enough for the alligator to turn around.
Dr. Martin has measured at least one den that was 4.6 meters (15 ft) long! He and his associates used tape measures and ground-penetrating radar to take these
measurements. 

Most of my other pages are arranged with the newest posts on top ( I figure that most folks are interested in current events.). But these den observations make
more sense arranged chronologically, so...that's how they re arranged on this page. I first described the story that started 12/29/2019 on the first "Dens" page.
When I found I'd gathered enough for a similar story at another den (which was about 40 yards East of this one), I put that onto its own page.  BBSP encountered
a major drought in 2022, which allowed water level in many of our lakes to drop by 3 or more feet. This exposed some of the previously submerged dens, including
the den in the story on the first page. I thought it would be interesting to show more about the exposed den, so I created this page to do it. 

First, a quick review of 2020. For the full story, go to this page.

01/19/2020  The morning of 1/19, I found the mother alligator in her spot. I could see a cloud of silt suspended in the water around her.  Over the previous weeks, I'd
guessed that she was digging in that spot--either making a hole, or a den.  The morning of 1/19, I found the mother alligator in her spot. I could see a cloud of silt 
suspended in the water around her.  Over the previous weeks, I'd guessed that she was digging in that spot--either making a hole, or a den. 
   

Mother alligator was sometimes visible, with her head at the surface as before; but then she'd submerge; and slide BACK INTO HER
BURROW. So, sometimes she was visible when visitors came by, and sometimes she wasn't.
      

01/26/2020  I visited the baby gators and their mom a week later. 

 

02/02/2020 Mom gator submerged at 10:30, then surfaced to breath at 10:50...about 20 minutes under water. 
    

 At 12:06, Mother submerged and backed into her burrow until she was hidden. She remained hidden until surfacing at 1:05---about 1 full hour under water!
     

02/16/2020  At 10:57 she swam back to the pod   From 11:01 - 11:05 mom moved back near the pod. She had been gone for 45 minutes!
    
     
03/15/2020   This day was the last day for me to visit Brazos Bend State Park for a while. With the warnings about the coming pandemic, and travel and social-
distancing protocols being put into effect, I had decided not to go to the park.  Over the weeks that followed,  protocols put into effect by the BBSP, and  the state 
took the decision out of my hands anyway.  So...this morning I was walking with 2 new volunteer trainees. I intended to show them the mom gator and her babies, but 
she wasn't there! 

10/16/2022  This summer, BBSP suffered from the same drought as the rest of Texas. There are other references to this on some of my other pages. The last
rain before this day was in mid August of this year, and there hardly any after that. Water in 40 Acre lake was at least 3 feet lower than usual. This den was
exposed, and is the same one in the images above and on the previous page. There are at least 2 reasons that the area looks different than in the pictures
above. 1) The exposed mud in the new pictures and 2) About 2 and 1/2 YEARS have passed since the older images.
   

There were two trenches, and multiple sets of footprints near, so I didn't approach too close to the den. The stick in the last image below is 6 feet long. I moved slowly
and carefully, then left quickly while intently watching the opening of the den.  Although I was very quiet, I was aware that my shadow could move across the opening
and bother anything hiding inside.
  

Two stitched panoramas below may help give some scale. This was the first day that I photographed the den, but I monitored it more after this.

12/25/2022  This was the last set of images of this den from 2022. They don't show much, but this was December, after all. Since I'm usually in this area about 
8am, and I'm facing West for the picture, my shadow is long and dark; and if I'm not careful, it can fall across the den. Temperature when I got of out my car 
was 37°F (15 minutes earlier), so I didn't expect to see the alligator (if it was in the den); but hoped to see its nose exposed for breathing. But it would hide if my 
shadow crossed the the den. No luck this morning. But...more to come in 2023!
    

The images above don't give a full picture of conditions at Brazos Bend on that day. It will take me a while to format everything that I observed and captured that
day and I hope show some of that somewhere on one of my pages (this is a reminder for me). But the images below will give some idea. All of them were taken 
close to 8:30am that day. Note that the water in the den opening was...water. But all around it, the water was frozen. The first two images below show the rest of 
40Acre lake. The third image shows the West end of Pilant Lake, on the North Side of the trail (40Acre Lake is South of the trail at this point.)
  

This shows a wide view of that entire area with the surface all frozen!

Closer to the Observation Tower (East of above), ice covered almost all of Pilant Lake. But I noticed something at the far edge of the water--about 800 yards away.
I needed optical magnification to see what was going on, and the images below show what I saw. The fourth image shows ducks standing on the ice.
   

A huge group of birds was floating in the remaining unfrozen edge of the lake.  If this seems odd (considering the cold), then remember that the ice is at or below
freezing (37°F, 0°C), but the water is warmer than that. I wonder if that crowd of birds soaking their feet and legs in the water also had any effect on the water and
helped keep it above freezing. Whatever the reason, the birds were there. So, with ice all around, the water in the den remained liquid. This could be because the
den was excavated into a bank that had good exposure to the sun. The den entrance-and the bank-gets direct sunlight. Direct radiation can heat the den, while it
can also be warmed by residual heat from the warmed dirt in the bank.  There was a lot more to see that day (another reminder for me to put it together).
   

01/01/2023  When I checked on the den today, I found signs that it was still being used.  The most obvious one was that large groove in the mud. That was 
probably a tail drag mark (possibly multiple drags going over the same spot?) made as the alligator moved in and out of the den. Multiple images to show from 
different perspectives. Since the den seemed to be inhabited, I didn't get very close. This was mostly so I wouldn't bother the alligator enough to make it feel 
threatened and then leave the den as an unsafe area.  I wanted it to stay.
    

01/08/2023  When I checked on the den today, I was happy to see signs that it was still being used.  The mud in front showed smooth spots from alligators sliding over
or lying on it. If it hadn't been used for a while, the den entrance and the mound (formed from the mud removed from the den) would be as dry and overgrown as 
the surrounding area. Also, note that this was all under water when the den was constructed (see above).
    

01/22/2023  When I checked on the den about 8:15am, I found a little bit extra. The carcass of some kind of mammal was floating in the water.  Unfortunately, as the
pictures show, I couldn't avoid having my shadow fall across the den opening. While I tried to get better telephoto shots of the carcass while adjusting the light
compensation, I saw the carcass move...just a bump, really. I was pretty sure that the alligator was in the den, so I backed away. I had to move on, anyway. For 
years I've heard that an alligator might store a carcass in its den and leave it to "ripen". But I've never seen it written anywhere, or observed it. In the book 
Biology and Evolution of Crocodylians by Grigg and Kirshner (2015) I found this: " It is known that crocodylians prefer fresh,rather than putrid, food, though they 
will eat carrion. There are no data to support the commonly held belief that crocs routinely stash a carcass to rot before they eat it." (page 193) For whatever
reason, there was a carcass with fur in the den that morning.  Unfortunately, I couldn't stay around to wait and see if the alligator would come out and eat. I went 
back a few hours later-about 1:30pm, and the alligator had come out of the den. I was happy to get pictures of the alligator and den together. 
    

I moved on after getting a set of pictures. The alligator was still out at 4:15pm. There's one picture below--note how the position of the shadow has changed. It's
hard to tell from the photos, but the alligator did seem to be a bit bloated. So, it could have eaten the carcass I'd seen that morning.
    

02/12/2023  When I checked on the den about 9:15am, I got a quick look at the tip of an alligator's snout, but it submerged. Betrayed by my shadow, again!  But when
I returned at about 1:30, the alligator was out on its mound. Since it had been out for a while, I thought that it might want to go back into the water, and hopefully, 
back into the den.  
    

About 30 minutes later, the alligator started to open its mouth, doing a "thermal gape"--showing that it was overheating. I was rewarded for my patience a few 
minutes later, when the alligator crawled into the den! I'd finally captured an alligator using a den on film!
    

02/19/2023  At 9:00, I checked the den, and again saw the tip of a gator's snout under the water. I took a few bad photos before the snout withdrew further into the
den. This time, I decided to wait until the alligator appeared. About 9:40, the alligator's snout appeared at the edge of the hole, and then it just stayed there.
    

Around 11:00, the entire head, and front legs emerged from the hole.  About 10 minutes later, the alligator crawled out of the den! It crawled out, curled around and layed 
down.  
    

But, apparently it didn't like the crowd of humans that were watching, so it crawled back into the den just a few minutes later. 
    

03/12/2023  Plants around the den have begun growing, and blocking the den from view. I can't see any definite signs that the alligator has pushed through the plants,
but I really couldn't see much at all. It might still be in there.  
  

03/19/2023  A cold front had passed through recently. This morning, the thermometer in my car showed 47°F. I didn't bother trying to record the air temperature 
on the trail because I was trying a new piece of equipment that I thought would give me related data.  I can say that It felt REALLY cold out there. I took the
images below with my phone, and with the new device.  I was trying out a FLIR one thermal camera which connects to the USB-C port on my phone. It has its own
optical camera, along with the thermal imager.
    

I decided to try to use the phone that is part of my camera, and after that the FLIR stopped working. I probably just needed to restart the camera, but that morning 
too much was going on.(For one thing, while I was holding my phone in one hand, and the FLIR in the other, a Bald Eagle flew right over me.) I was still learning 
about the FLIR one, so I didn't use it more that day. BUT, I got these thermal images, and they are really interesting. So, the imager works off of surface temperatures,
so air temperature will not register. In the images looking down at the den opening the device snagged a 35.8°F and a 57.6°F high and low. The imager is always
sampling, so these points can fluctuate as I move the camera around.  The 35.8°F isn't really a surprise-I said it was cold. But look at the reading off the water in the
den!  It was 21.8 degrees warmer in the den than the lowest measured spot!  The den opening is obviously warmer than the surrounding area.  It's one thing to 
read about how an alligator's den is an environmental control chamber, but it's amazing to actually see it demonstrated in the field!  There are many reasons for
this temperature difference.  The sun shines on the bank for most of the day.  Water and dirt can work as insulators, and also as heat storage. It hadn't been cold 
for weeks, but only for a day or two. What else can be warmed by the sun?  The alligator!  If this alligator was able to spend time in direct sunlight, then its skin-
and the osteoderms-would have been warmed by the infrared. The alligator's blood would circulate past and through the warmed structures, carrying warmed 
blood into its body. Given enough time, the alligator's internal temperature could be warmer than the surrounding air...or the surrounding water. A solar-heated alligator
making multiple trips to an enclosed water vessel (which the den was then) could warm the water in the den, and give the effect I saw in the thermal image. This is 
just a guess. I haven't read anything about anything like this in relation to alligators. But, I have read about a species of snake that basks to raise its body temperature,
then returns to its burrow to warm its eggs. Females of this species temporarily turn black during the reproductive cycle for more efficient heat absorption. It's 
described in this study: "Reproductive biology and maternal care of neonates in southern African python (Python natalensis)", G. J. Alexander,  2018. So heat being 
transferred from a reptile to its environment-instead of the reverse-isn't such a strange idea.
I'd hoped to take further thermal shots of the various lakes that day-because of the cold air-but no luck.  Maybe next time.  By the way, I saw slight movement in the water 
down there, so I think the gator was home.  The two images below demonstrate the "overlay" ability of the camera. With so many subjects (leaves, branches, etc.) in the
vision field the composite image is a bit too cluttered. As with any device, more experience will give better results.  Still....not a bad try. 
   

Update 07/14/2023 Using the FLIR software, I can add test points, clarify images, and create reports. These images show more information. Click each one to see it larger. pic 1 pic 2 pic 3
   

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