The Urban Alligator – Part 2

Written by Mark Kramer

Females may lay 30-60 eggs | Photo by Mark Kramer

It’s been two months since we last checked in on our Armand Bayou alligator nest. Over these months, the eggs have been incubating through the summer under mom’s watchful eye. Hopefully, there have been no flooding rains through the summer. Reptile eggs have a leathery shell and the developing young “breath” through the eggshell. If they become submerged, the young will drown inside the egg. The growing young certainly dodged a bullet from the near miss of Hurricane Laura. Hopefully, there have been no raccoons or other marauding scavengers.

After a 65-day incubation, hatchlings emerge from the egg | Photo by Mark Kramer

Alligators are unusual among reptiles in that the hatchlings remain protected by mom for the first year of life | Photo by Gary Seloff

Even with a fiercely protective two-hundred-pound mother reptile watching over you, the first year of life is the most treacherous | Photo by Gary Seloff

August 15-30 is the time that alligator eggs begin to hatch on Armand Bayou. Before the young emerge from the egg, they begin to vocalize. The chirping calls signal to all brethren that today is the day to hatch. The young begin to dig their way out of the nest. Mom is nearby and may offer some assistance if needed. She carefully digs the nest apart and may carry the young in her mouth to the waters edge. 

Hatchling alligators are 8-10 inches long and vulnerable to predation. They may be a meal for Great Blue Herons, Wood Storks, Raccoons, Bald Eagles, or even other Alligators. 

What you eat depends on how big you are. This alligator has caught a Common Merganser | Photo by Gary Seloff

Alligators are carnivores and will eat as large of a prey item that they can kill and tear apart. For a hatchling gator, that means a typical meal may be dragonflies or minnows. With adequate food, they can grow as much as a foot per year. This growth rate continues until the animals reach sexual maturity which occurs at around 6-7 feet long. After that, growth continues throughout the animal’s entire lifetime. They never stop growing, but growth slows after maturity. This lifelong slow reptilian growth is called indeterminant growth. It also means that the older the animal, the more time you have to grow really big. 

Big gators will eat smaller gators | Photo by Gary Seloff

Alligator hatchlings will remain with their mom for around a year after hatching. Once they lose the protection of their mother, the game changes and becomes even more treacherous. Big alligators will eat smaller alligators. This strategy of cannibalization supports the moving of energy from lower in the food chain up to the breeding sized adults. It also means that local alligator populations maintain stable populations.

Alligators have an incredible bite force when their jaws snap closed | Photo by Gary Seloff

When ranked among all animals on earth, Alligators come in at number three on the list of strongest bite force. Alligator teeth are cone shaped and designed to grip and puncture flesh (not cut as shark teeth do). After they kill, the teeth are used to perforate tissue and then-tear along the dotted line.

Crocodilians have one the most acidic digestion systems of any animal and are capable of digesting large bones like this deer leg | Photo by Gary Seloff

In Cajun Country, if you want to make a person disappear, you feed them to the alligators. This is what you will look like | Photo by Mark Kramer

I found this young alligator on the West Bank Road a half mile from the nearest water. He ran into the prairie when he saw I was approaching. He quickly became entangled and stuck in the dense grass and couldn’t move. He was relocated to a happy home in the bayou | Photo by Mark Kramer

Leaving home is tough for a juvenile alligator. If you are a juvenile alligator (under six feet) without maternal protection, you are at risk of being eaten by a larger alligator. This is a strong motivation to head out on your own. Many juvenile gators leave their home waters, trekking forth across dry land in hopes of finding another suitable water body which is free of larger alligators. This perilous venture is a great risk. Many youngsters never find water. This behavior also serves the species by promoting dispersal of alligators into new territory. Several of these rogue juveniles show up in nature center ponds every summer. Remember, just because there was no alligator in that pond yesterday doesn’t mean there won’t be one there tomorrow.

Alligators eat turtles, but somehow these turtles know that alligators don’t eat through the winter | Photo by Ann Brinly

Houston’s first cool fronts arrive in late September. It always amazes me how quickly water temperatures drop in October. Water temperature is the driving regulator behind the level of activity a gator can maintain. As bayou water temperatures drop into the upper sixties in late October, gator activity begins to slow down. In fact, alligators usually have a final Fall meal and begin to think about a plan for winter.

Alligators dig a den or cave which they spend the winter in | Photo by Mark Kramer

Once completed, it will be used for years to come. The den is flooded with shallow water and maintains an air space at the top of the cavern. Often, the entrance is located below water level and is not clearly visible. A typical den is located in close proximity to the nest site. Alligators have high site fidelity and build their nests in relatively the same location every year. It is to the gator mother’s advantage to not have to lead her young over a long distance from the nest to reach the den. It is believed that females are the primary builders and users of dens, but the ecology of alligator dens is still poorly understood.

As Fall temperatures drop, mother and hatchlings enter the den for a long winter’s nap | Photo by Ann Brinly

Several generations may occupy the den with her. On early Spring sunny days, the young emerge and sometimes create a basking “pile up”. | Photo by Gary Seloff

Alligators are remarkably resilient and endure extreme winter temperatures. The den buffers the harshest cold temperatures, but conditions are difficult. Alligator winter core body temperatures are approximately the same as the water (that’s cold!). There have been numerous documented accounts of alligators trapped in shallow, ice-covered ponds with only their nose above the ice! 

Armand Bayou gator populations are healthy | Photo by Gary Seloff

Armand Bayou now has a healthy population of alligators. After decades of recovery, there are abundant gators of all sizes. This diversity of all alligator age classes is one barometer to measure the health of the population. In an effort to better understand the unique characteristics of Armand Bayou’s gator population, a study was conducted. In 2011 and 2012, ABNC partnered with Texas A&M University graduate student, Cord Eversall, to research the details of the population.

Photo by Mark Kramer

For two years, nighttime spotlight counts were conducted via pontoon boat and canoe. All crocodilians share an unusual characteristic. Their eyes have a strongly reflective property when spotlights are shined on them. This “stop sign red” reflective property is visible for several hundred yards. It gives relatively accurate information as to the number of alligators in a field of view, but it does not gauge the size of the animals. The size of an animal in the water can only be estimated by a good look at the size of the gator’s head. The distance between the eye and the nose measured in inches approximates the number of feet in total body length. For example, six inches between the eye and nose equals a six-foot long alligator. Following are several graphs which show some of the results.

Staff and volunteers counted alligators throughout the watershed

All sightings during the survey

While it’s clear that the bayou is populated with numerous subadult alligators, those found of breeding age were relatively low

Photo by Mark Kramer

My family is from south Louisiana and moved to Pasadena in the early 1950’s. This photo was taken from the banks of the Mississippi River near my Mother’s childhood home. There were many stories of alligator hunts where hides were sold at market. This unregulated hunting pressure was the primary factor in alligator populations crashing. Their populations have now fully recovered. This keystone species and apex predator of the Bayou City plays a critical role in keeping the balance in bayou ecosystems. Today, Harris County is the third most densely populated county in the U.S. and has altered most every local bayou’s hydrology through channelization. Urban alligators only occur where people make room for to them coexist. Habitat loss (in this case, alligator habitat) is recognized as the single biggest ecological threat around the world. Armand Bayou remains un-channelized and is the most beautifully preserved and ecologically intact bayou in the Bayou City. Even more beautiful with the return of the Urban Alligator.

For more on Armand Bayou alligators, check out this YouTube video:

Bayou City Eco-Almanac-UHCL Alligators