Alligator locators
Counting the creatures lurking in Brazos Bend State Park is a family affair
Seated in an elevated captain’s chair with a 500-horsepower engine inches behind his head, Barry Eversole eases forward on the accelerator as the engine roars to life, plunging the airboat into the water. The pistol on his right hip pushes into the seat cushion as he shifts to get a better view through the tall vegetation.
In the front seat, wearing a green ball cap and sunglasses is Barry’s son, Cord Eversole, a professor of wildlife ecology at Stephen F. Austin State University. Along with his father, a game warden with Texas Parks and Wildlife, Cord is monitoring the alligator population at Brazos Bend State Park in Fort Bend County.
Barry and Cord are the fourth and fifth generation of their family to grow up in this part of Southeast Texas. In Barry’s lifetime, he’s seen alligators go from being so rare they were classified as endangered to so common he regularly responds to calls about them in people’s yards. Today, alligators face the new threats of extreme weather and invasive species that may prove to be the last straw for these ancient reptiles.
I’ve joined Cord and Barry to check on the status of the alligator nests in Elm Lake, the largest body of water at Brazos Bend. It’s a place I know well. I bring my students here every semester as part of a course I teach in ecology and evolutionary biology at Rice University. On weekends, I often come with my family. With both my students and my kids, an alligator
sighting is the highlight of any visit.
Barry navigates the airboat through the lotus and water hyacinth blanketing the water’s surface. Elm Lake is the largest of the eight lakes at Brazos Bend, all home to alligators, in addition many types of fish, crustaceans, insects, birds and mammals.
The survival of alligators has implications for the entire wetland ecosystem, which in turn affects flood control. They create habitats for a variety of species: Their movements help maintain low areas where water can accumulate, creating habitat for aquatic plants, fish and wading birds, while their nests provide shelter for other wetland species, such as turtles.
As top predators, alligators also maintain a healthy balance among wetland animals, such as crayfish, frogs and muskrats, and control populations of invasive animals, including nutria and feral hogs. Despite their importance, alligators were nearly exterminated in the first half of the 20th century due to habitat loss and overhunting as demand for their hides surged. They were listed as federally endangered in 1967.
The protection worked. Populations across the southeast United States recovered, and alligators were removed from the endangered species list in 1987. In Texas, alligator populations are now carefully managed, with hunting allowed seasonally. Brazos Bend is one exception, and it has allowed the park to serve as a sanctuary for the species.
“There’s a really good number of people specifically here wanting to see some alligators out in the wild,” Jason Castle, assistant park superintendent, told me by phone. “Usually the first question people ask is, ‘Where can I see alligators?’ ”
While alligators are often portrayed as dangerous, according to Castle, no visitor to Brazos Bend has ever been injured by an alligator. He attributes the park’s safety record to educating visitors about “alligator etiquette.” Visitors are advised to stay at least 30 feet from alligators, and park rules prohibit swimming and boating.
As a game warden, Barry Eversole is one of the few people authorized to operate a boat within Brazos Bend. It’s familiar territory for Barry, who grew up nearby.
“I’ve been around alligators all my life,” he said. “I rode my bicycle all over this place before there was ever a park. There were always alligators here. They’ve always been a part of my world.”
Like his father, Cord became interested in alligators at a young age. “Growing up, this was a rural county,” Cord recalled. Alligators were common in the ponds and creeks near his home. Then came the uptick in development when he was a teenager.
“Subdivisions were being put in places that were historically swamps,” he said. That led to more encounters between alligators and people. Cord often tagged along with his dad on calls to relocate “nuisance gators” from the new developments. As a teenager he also volunteered with Brazos Bend’s assistant superintendent at the time, Dennis Jones, who kept tabs on alligator nests.
“I remember us walking along one of the islands at Elm Lake. We passed over an alligator’s nest and went all the way to the end of the island. As we were coming back, the alligator became aware that we were there and started high-walking up toward the nest. Cord was a little intimidated, but I imagine he’s probably outgrown that now,” Jones said, laughing.
He has. Cord went on to earn a bachelor’s, master’s and PH.D. in wildlife science from Texas A&M University-kingsville. For his dissertation research, Cord returned to the wetlands of his childhood. He knew there were plenty of alligators there — yet no one knew exactly how many.
Earlier surveys of alligator populations at Brazos Bend followed a standardized
protocol with surveys conducted just after sunset. Alligators have a reflective surface on the back of their eyes, so shining a spotlight across the water makes their eyes appear to glow. Cord extended the standard survey time and found a greater number of alligators, particularly adults, later at night.
His work also highlighted the important role that reproduction plays in maintaining alligator populations. The historic drought in 2011 hit alligators hard. The number of nests at Brazos Bend increased as alligators poured in from surrounding areas where water became scarce. But few of the eggs laid that year survived. Even eggs removed from nests and incubated in a lab had low hatching rates.
Cord attributed this to stress caused by alligators crowding into the few remaining bodies of water, which led to territorial battles and competition for food.
Eggs left in nests fared even worse. Alligator nests are made of piles of vegetation that protect the eggs both by insulating them and by generating heat as the vegetation decays.
“You can put your hand into the nesting material and it’s hot,” Cord said. “If you ever put your hand in a compost pile or into mulch, it’s the same process. That heat, that’s what incubates the eggs.”
But without much rainfall in 2011, the nests dried out. Alligator eggs are particularly sensitive to changes in temperature
and moisture. Not only can the eggs fail to hatch if conditions aren’t right, but an individual alligator’s sex is determined by the temperature of the egg at a critical time during the embryo’s development.
“Minor changes in nest temperature can really skew sex ratios,” Cord said.
Having such strict nesting requirements is a liability in an era of extreme weather. In the decade he has been monitoring alligator nests, Cord has seen how both droughts and floods can lead to nest failure. In 2016 and 2017, floodwaters destroyed many of the alligator nests at Brazos Bend. Last year, the nests flooded again. This year, Cord and Barry feared the same outcome but for the opposite reason — drought and record high temperatures threatened to dry out the nests, as in 2011.
“Just in the last two years we’ve had extremes on both ends of the spectrum,” Barry said. “We were flooded out last year. This year we burned up.”
If nests fail too often, it can threaten the future of the entire population. “If it happens in one year, it may not be a huge deal in the grand scheme of things,” Cord said. “If it happens for a couple years, they might be able to bounce back. But if it happens year after year after year, species can’t persist with failure time and time again.”
Cord has been concerned about the prospects for the eggs laid this summer. “I measured the moisture content of the nest material and it was bone dry,” he said.
We spot our first alligator in a stretch of water covered in tiny, green duckweed. At first, only its eyes and nostrils are visible above the surface, but as it slowly swims away, we catch a glimpse of its full snout, back and tail.
It’s difficult to estimate the size of an alligator when it’s submerged, but Cord and Barry tell me that the number of inches between an alligator’s eyes and nostrils is about the same as the length of its entire body in feet. By the looks of it, this one is about 3 feet long – fairly small.
Cord explains that young alligators grow about a foot a year, which makes this alligator about 3 years old. They become reproductively mature at about 6 feet. That takes six years in other populations, but because there are so many alligators at Brazos Bend competing for resources, it can take them twice as long.
Barry circles the boat around and pulls up to the edge of a narrow island covered with thick vegetation. There’s a small clearing with a pile of sticks about 4 feet across — an alligator nest.
Barry cuts the engine and we remove our earplugs. Cord steps out and carefully places his rubber boot on the soggy cutgrass while his dad keeps watch from the captain’s seat. Ordinarily, approaching an alligator nest would be a foolish thing to do. But Cord explains that the alligator nests on islands in Elm Lake are safer than others.
“These islands are literally surrounded by a moat that’s got alligators, so it’s very unlikely that a raccoon is going to make it across,” says Cord. The lower risk of nest predation has made these gators less protective of their nests. As a result, eggs laid in these nests are not only easier to monitor but also more likely to survive.
“This is an alligator factory,” Cord said, gesturing first to our island then to another one nearby. But despite the nearly ideal nesting conditions, even Elm Lake’s alligators face challenges.
“These islands have a lot of vegetation to build nests,” Cord explained. “But we have a problem with invasive plant species here. Nests made of Bermuda grass or Chinese tallow don’t typically hold their moisture very well and don’t maintain temperature very well.”
Invasive plants. Drought. Floods. Habitat loss. The list of threats to alligators just keeps growing. And yet here we are, face to face with one of the few nests made this year at Brazos Bend.
I step out of the boat to take a closer look, following carefully in Cord’s footsteps. The nest is directly below a Chinese tallow tree, and the nest appears to be made largely from tallow branches. Cord bends over and picks up what looks like a piece of white plastic trash — the remains of a justhatched alligator egg. Around his boots are at least a dozen more.
Cord shakes his head and makes an entry in his notebook. “Signs of life,” he said with a chuckle.