New in Town
Texas’ landscape features an ever-evolving roster of species.
by Russell Roe and Cullen Hanks
From his backyard, Travis LaDuc of Austin can’t necessarily see the changing nature of Texas wildlife, but he can hear it. The Rio Grande chirping frogs around his house, emitting a chorus of high-pitched chirp-chirp-chirps, weren’t there just a few years ago.
“I hear them all summer now,” he says of the little frogs, which have been expanding their range across Texas from their Rio Grande Valley home. “It’s pretty remarkable going from having a fairly quiet backyard to having all these little guys peeping and squeaking.”
Nature isn’t static; it’s always changing. It always has been, and it always will be. Species are constantly colonizing new areas, adapting to new conditions. The mix of plants and animals you see around you is not what people saw 100 years ago, and it won’t be what people will see 100 years from now. Some species will be the same, some will be lost, and others will appear.
“Things change every day, every month, every year,” says Shaun Oldenburger, who manages programs for migratory game birds at the Texas Parks and Wildlife Department. “It’s an ever-evolving landscape.”
We know from the tracks at Dinosaur Valley State Park that dinosaurs walked where we walk today. When prehistoric humans settled in Texas, they found mammoths, camels and saber-toothed cats.
Consider that 99.99 percent of all species that have lived on Earth have gone extinct. Change is essential to the drama and beauty of nature, even if that change is not always pretty. When change happens too quickly, the results can be devastating, as when a massive asteroid 66 million years ago caused the extinction of three-quarters of Earth’s plants and animals, including the dinosaurs.
Humans are accelerating ecological change. We remove established species, introduce new species, divert the flow of water, manipulate the topography and alter the ingredients of our soils. In doing so, we are rapidly changing the playing field for life in Texas. Some species are benefiting from these changes, while others are losing ground. We optimistically expect our native species to keep up.
We plowed the prairie and, in doing so, eliminated habitat for the greater prairie-chicken and the crawfish frog. We built reservoirs and ended up attracting flocks of double-crested cormorants. We planted trees in Lubbock and created habitat for the eastern gray squirrel.
As an observer, understanding the nature of change is difficult. In our short lives, we see only a snapshot of time. The arc of change is incomprehensible from our personal experience. Even as we accelerate ecological change, the impact of our actions today may take generations to play out.
Some of these changes have had negative consequences. Zebra mussels, for example, have clogged our waterways and caused declines in fish and native mussels. In other cases, too, new arrivals have disrupted ecosystems and displaced native wildlife.
It’s difficult to untangle the web of cause and effect that led to the mix of species we see today. Tragically, iconic species that once defined the character of natural regions have been lost not only from the landscape but also from the collective memory of generations of Texans. Wild bison and gray wolves are gone; it’s possible that ocelots and the Houston toad won’t survive into the next century. This loss of our authentic heritage fuels fear of change and fear of a future devoid of ingredients that are uniquely Texan. However, change is also part of the beauty of nature and certainly a key ingredient of the nature of Texas.
Eastern gray squirrel.
Many established non-native species are integral to the Texas experience that future residents will know and love, such as the armadillo. More species will come, brought by humans or arriving of their own volition, and some of these species will also become part of the nature of Texas. The future will look different, but it need not be bleak.
It’s an interesting problem for those working in the conservation field. Isn’t conservation by definition focused on preventing change, on preserving what’s here now?
“That’s the challenge,” Oldenburger says, “coming to a consensus on where to allow change to happen.”
Today’s conservationists face the complex task of not freeze-framing an ecological status quo but instead seeking to protect and perpetuate dynamic and ongoing wild processes in which rivers flow, rocks erode and species come and go. Conservation must aim at a moving target.
We’ve chosen three species — the armadillo, the Rio Grande chirping frog and the white-winged dove — to help illustrate our changing world.
Few species of mammal have more Texan credibility than the official state small mammal, the nine-banded armadillo. Yet many people don’t know that it is a newcomer, a colonizer from Mexico.
“Armadillos play a significant role in our culture,” says Jonah Evans, TPWD mammalogist. “They’re iconic.”
When Texas declared its independence in 1836 the closest armadillo may have still been in Mexico. Armadillos were first recorded in South Texas in 1849. By the early 1900s they had expanded to the Austin and San Antonio regions, and by the 1950s they had staked claims across East Texas. By the 1970s, our little armored friends were found in Oklahoma and Arkansas. “Home with the armadillo” didn’t mean just Texas anymore.
After armadillos made it across the Rio Grande, they were boxed in by the South Texas grasslands. Over time, mesquite and brush began to displace the grasses because of drought, grazing, farming and fire suppression. The new woody habitat, which allowed armadillos to forage in forest litter, was more suitable for northward-bound armadillos than the grasslands.
“It’s not like armadillos learned a new trick,” Evans says. “The environment changed and allowed them to use the tools they have to be more successful than they used to be.”
Evans says the success of the armadillo follows a trend in determining which mammals will do well in a state where humans have reached every corner. Armadillos, like raccoons and coyotes, are generalists. They do well in a wide range of habitats, and in disturbed habitats. Specialists such as the swift fox and kangaroo rat, which depend on specific diets and habitats, tend to suffer when habitat conditions change. The generalists will continue to have an advantage in today’s world.
Texas lost several mammals to extinction in the 20th century. The grizzly bear, jaguar and black-footed ferret all disappeared, largely because of human-induced changes. Other mammals experienced drastic range reductions, including the pronghorn, mountain lion and black-tailed prairie dog. As for mammals that have been spreading, porcupines and a few species of bats joined the armadillo in expanding their territory.
Rio Grande Chirping Frog
There’s a hitchhiker making its way across the state. It hides out in potted plants at nurseries. It’s small, typically three-quarters of an inch in length, and it doesn’t need water to lay eggs. It’s the Rio Grande chirping frog.
These little guys are native to the Rio Grande Valley but have been popping up and hopping around in places like Houston, Huntsville, Fort Worth and Tyler.
“The plant nursery trade is probably a pretty good mover of these guys, as well as construction material,” says Travis LaDuc, curator of herpetology at the University of Texas at Austin’s Biodiversity Collections.
In 1987, the frog was found in four South Texas counties. In 2000, 11 counties. Today, it has spread to 28 counties, including places in North, Central and East Texas.
LaDuc discovered the first Travis County specimen in 2013 in a debris pile across town from his home. Now he hears the frogs in his backyard.
These frogs have been thriving in places they didn’t exist just a few years ago, but they didn’t do it on their own. Biologists suspect that when tropical plants are shipped out of South Texas, the plants carry hidden cargos of chirping frogs. When the frogs reach their new destination, they find irrigated landscapes and plenty of places to hide. Urbanization takes a heavy toll on many wildlife species, but this one seems to do just fine in the city.
Rio Grande chirping frog.
One of the unique attributes of the Rio Grande chirping frog is that it doesn’t need water for reproduction. Its young do all their development inside the egg, emerging as little froglets, instead of developing from larvae to tadpole to frog in a pond or other body of water.
“That really facilitates their ability to move around,” LaDuc says.
Biologists aren’t completely sure how the frogs are interacting in their new environments — whether they have found their own niche or are competing with other species.
The Mediterranean gecko, a non-native that has firmly established itself in Texas, moved into a niche with little competition.
“There’s no other nocturnal lizard that lives on vertical surfaces in Texas,” LaDuc says.
However, the brown anole, an introduced lizard species spreading in Texas, has been pushing out a native, the green anole. When the browns move in, the greens are forced to move further up the canopy.
The white-winged dove is a relative newcomer to our urban areas, but it has come to love the city life.
“These birds do really well in cities,” says Cliff Shackelford, TPWD ornithologist. “There are lots of canopy trees and plenty of water — and bird feeders. Sometime in the 1980s, they exploded in San Antonio and Austin and started marching northward, triggered by urban development.”
For generations, these were country birds, occupying Rio Grande Valley brushlands and serving as an important game bird for hunters.
What happened? With conversion of their native brushlands to farming and with freezes to citrus groves where they nested, their population was in decline.
In the 1950s, the situation was so dire for the birds that TPWD established the Las Palomas Wildlife Management Area in large part to protect white-winged doves. At some point, white-winged doves learned to live in urban environments. Now the white-winged dove population in Texas is nearing 9 million.
“No one would have ever guessed that,” Oldenburger says of the rapid expansion.
Urban and suburban development attracted the birds to a habitat of neighborhoods lined with shade trees and filled with backyard feeders.
“Every city they hit, they found what they needed,” Shackelford says.
Their northward spread has been fast and remarkable. Texans from San Antonio to El Paso to Wichita Falls now can hear the white-winged dove’s who-cooks-for-you cooing outside their bedroom windows.
Another resident of the South Texas brushland, the great-tailed grackle, has found similar success in cities. The grackle has readily adapted to human changes in the landscape, to the dismay of many who have parked their car under a grackle-filled tree.
Monk parakeets love the cities, too. Originally from South America, they were introduced to Texas by the pet trade and are thriving in urban areas. They make their nests in stadium lights and power poles and delight many Texans with their bright green plumage.
None of these birds — the grackles, doves and parakeets — are native to Houston, San Antonio, Austin or Dallas, but now all three are part of the fabric of our cities.
By documenting where species are today, and comparing today’s information to data collected by previous generations, we can start to see the arc of change in our natural world. Programs such as iNaturalist, eBird and TPWD’s Texas Nature Trackers invite the public to participate in recording where species currently exist. The naturalists a century from now will have a much clearer view of the ecological change we are participating in.
By documenting plants and animals, Texans can help the conservationists of today and of the future be good stewards of wild plants and animals. Through informed stewardship, we can do our best to provide our native species a path into the future and make sure future generations inherit a natural world that is more abundant, resilient and diverse.
It can be difficult sorting out everything involving natives, non-natives, invasives, climate change, urban expansion, habitat destruction and all else going on in the human and natural worlds.
As more and more people move to Texas and lay an ever-heavier hand across the landscape, affecting wildlife and plants in increasingly dramatic ways, aren’t humans the species that needs to be held in check?
Robin Doughty, a professor of geography at the University of Texas, isn’t so sure.
“We have the ability to be very creative as well as destructive,” he says. “We are part of the system. I don’t like thinking of us as an invasive species — it doesn’t sit right with me. I rather see us as co-creators, intelligent beings who can recognize and value and trust nature, and watch it. And adjust. We need to adjust. We’re not good at that.”