Invasive species: How the tegu lizard could invade the South

With the tegu’s successful occupation of Florida’s ecosystems, a new study predicts that this invasive species could potentially spread across the southern U.S. and into Mexico. But these voracious lizards are just another incident in our devastating history of invasive species.


Take a moment to consider your perfect neighbor. I'm going to assume the image you conjured wasn't a 4-foot lizard with an insatiable appetite, giant claws, and a powerful tail it can ferociously whip at aggressors. Unfortunately, that's exactly the neighbor Floridians got.

Known as tegu, these giant South American lizards have recently moved into Florida's ecosystems, becoming one of the state's most aggressive invasive species. But they may not just be Florida's problem for long. A recent study published in Nature modeled the potential spread of the species and found that these lizards could extend their range far beyond the Sunshine State.

The tegu cometh


(Photo Mike Baird via Flickr)

Like many other invasive species, tegus came to the United States as pets. As cited in the study, reptiles are incredibly popular on the international pet trade. Between 2000 and 2015, as many as 79,000 live tegus may have been imported into the U.S.—with an undetermined number breed in captivity.

Individually, exotic pets like tegus aren't much of a problem. However, they quickly become one when they either escape their enclosures or are released into the wild by owners unwilling to continue their care.

If enough are released, these animals may develop breeding populations in the region, escalating from nuisance to invasive species. Since invasive species are not native, the ecosystem provides no evolutionary checks and balances, leaving the invaders free to breed, feed, and spread aggressively.

In fact, the National Wildlife Federation estimates that “[a]pproximately 42 percent of threatened or endangered species are at risk due to invasive species."

This cycle is especially taxing on Florida's ecosystems, where reptiles can easily thrive thanks to a combination of subtropical climate, habitats similar to those they left, and relatively few native competitors. The state is also a central hub in the exotic pet trade.

To date, two tegus species have set up shop in Florida: Salvator merianae (the Argentine black and white tegu) and Tumpinambis teguixin sensu lato (the Colombian gold tegu). They pose a significant danger to many local species—such as alligators, turtles, and ground-nesting birds—as these long-clawed lizards can easily dig up nests to devour eggs.

“They are voracious, omnivorous predatory lizards that can live in a variety of habitats, but we can't know what is going to happen or how intense this invasion is going to become until the effects are upon us," Lee Fitzgerald, a professor at Texas A&M University and study co-author, told Reuters.


Not your dream neighbor: A male Argentine Black and White Tegu (Salvator merianae) mounts a female that has been dead for two days and attempts to mate. (Photo by Ivan Sazima via Wikimedia Commons)

Fitzgerald and his co-authors built species distribution models and projected those models onto North America to estimate the prospective range of the tegus. They found that much of Mexico and the southern United States would provide suitable habitat for at least one species of tegu.

The study also notes that there are “no known localities where tegus have been extirpated as a result of hunting" and that “[u]nder climate change scenarios in North America and the potential for niche shifts to occur, the invasion of tegu lizards could possibly be even more extensive than our models indicate."

Of course, tegu are not the only invasive reptiles to wreak havoc on Florida's delicate ecology. The state hosts a population of Burmese pythons that have turned the Everglades into their personal sex pad.

Like the tegu, this snake species was imported into the U.S. as a pet. After enough either escaped captivity or intentional release, they managed to establish a breeding population. Who knew caring for a 12-foot, 70-pound snake would be so difficult?

Also like the tegu, these pythons prey on native species that have no natural defenses against them, while simultaneously outcompeting local predators for resources. As cited by the United States Geological Survey, a 2012 study showed populations of raccoons, opossums, and bobcats have dropped 99.3, 98.9, and 87.5 percent respectively in the southernmost regions of Everglades National Park. Marsh rabbits, cottontail rabbits, and foxes have effectively disappeared from this region.

Tegu lizards: One link in a destructive chain

Florida may be a special case, but it hardly stands alone. In the United States, there are approximately 50,000 non-native species. Of those, roughly 4,300 are considered invasive. Every state plays host to invasive species and not just reptiles. Non-native birds, fish, mammals, and even plants have massively damaged local ecosystems.

English ivy, for example, was originally introduced to North America as an ornamental plant designed to elicit images of quaint English cottages. Today, it is a threat to biodiversity in the Pacific Northwest, where it grows uncontrollably, suppresses native vegetation, and destroys wildlife habitat.


English ivy. (Photo: Creative Commons)

But the onus doesn't just fall on negligent gardeners and pet owners. Invasive species have been introduced to the United States through a myriad of routes: from commerce (the nutria was bred for its fur) to land management (Asian carps were introduced to control weeds and parasites in aquaculture) to complete and total accidents (the emerald ash borer is believed to have immigrated on wooden packing materials from China).

Even Shakespeare enthusiasts shoulder some of the blame. In the 19th century, the American Acclimation Society deemed it necessary to introduce North America to every bird mentioned in the Bard's oeuvre. Its members released skylarks, nightingales, and song thrushes. None of them survived.

Then, in March 1890, a society member named Eugene Schifeffelin released 60 starlings into Central Park. Today, there are millions of the poxy birds devouring crops, spreading disease, and competing with native species across the continent.

Invasion of the birdy snatchers

But let's not look to the follies of others and shake our heads with too much haughty superiority. If you are American, there's a good chance your household is one of the 30.4 percent harboring the country's most pernicious invasive species. I am, of course, talking about the house cat.

Cats were introduced to North America by European colonialists, and thanks to our patronage, these cuddly killers have enjoyed an evolutionary free ride. Today, there are more than 100 million feral and outdoor felines roaming our parks, neighborhoods, and backyards, killing more than a billion birds annually. When other taxa are considered, the average outdoor cat kills around two animals per week, for a yearly kill count of more than a hundred critters.


(Photo: Creative Commons)

Consider the story of Tibbles the cat. Tibbles was brought to Stephens Island, New Zealand, by her owner, a local lighthouse keeper. She was the first mammalian predator to ever live on the island, so local bird species had not evolved the necessary defenses. The Stephen Island's wren didn't even fly because it had no need to. Within a year or two, Tibbles and her offspring would hunt the Stephen Island's wren to extinction and push several other species to the brink.

While the Tibbles case is extreme, the level of predation brought on by cats is ruinous. The problem is so bad that the Western Governors' Association listed feral cats as one of its top 50 invasive species concerns. With the addition of climate change and habitat loss, many bird species are being decimated at unsustainable levels.

If you're a dog lover, this may seem the perfect opportunity to lord it over your furball-loving friend, but hold off. While the canine isn't considered invasive to North America, the species can still massively impact biodiversity and impede recovery efforts.

In India, dogs reportedly attack 80 species, of which 31 are threatened and four critically endangered. Another study found that “[d]ogs have caused around 10 extinctions and threaten another 156 species" and lists canines as one of four species with the most pervasive ecological impacts—the others being cats, rats, and pigs.

Pushing back the invasive tide

Want to help mitigate the impact of invasive species in your region? The U.S. Fish & Wildlife Service has an excellent guide for how to prevent introducing invasive species and what to do if you recognize one. For information more specific to your area, you can contact your local USFWS office or visit its website.

Here are some general guidelines to follow:

  • Learn how to identify invasive species in your area and whom you should report them to.
  • If you are a landowner, learn what steps you can take to properly manage invasive species on your property.
  • Don't bring foreign plants or animals into the country without legally declaring them. Don't purchase from illegal vendors.
  • Favor native plants in your gardens and yards, and thoroughly research any non-native species you plan to introduce.
  • Cats should be spayed/neutered and kept indoors. Dogs should be kept on a leash during walks, and owners should clean up after them to prevent spreading disease.
  • After traveling to other regions, be sure to clean the mud and dirt from your shoes and clothes. Seeds of non-native planets can easily travel this way. The same goes for vehicles.
  • Boats and aquatic gear should be thoroughly cleaned and drained before leaving a site.
  • Consider the lifecycle and needs for any animals you plan to purchase as a pet (exotic or domestic).
  • Do not release pets into the wild if you can no longer care for them. Find a suitable location to surrender the animal. Many states have amnesty days where an exotic or illegal pet can be surrendered with no questions or punishments.

The one thing all invasive species have in common is that they were introduced to their new homes by human activity. Given the vast reach of globalization—not to mention mishaps, accidents, chance occurrences, and blatant disregard—invasive species will no doubt continue to be a problem well into the future. However, with these simple steps, a little knowledge, and some forethought, we may be able to prevent at least some invasions on the potential scale of the tegu.


(USAF photo by Robbin Cresswell)

Stand up against religious discrimination – even if it’s not your religion

As religious diversity increases in the United States, we must learn to channel religious identity into interfaith cooperation.

Sponsored by Charles Koch Foundation
  • Religious diversity is the norm in American life, and that diversity is only increasing, says Eboo Patel.
  • Using the most painful moment of his life as a lesson, Eboo Patel explains why it's crucial to be positive and proactive about engaging religious identity towards interfaith cooperation.
  • The opinions expressed in this video do not necessarily reflect the views of the Charles Koch Foundation, which encourages the expression of diverse viewpoints within a culture of civil discourse and mutual respect.
Keep reading Show less

Why Epicurean ideas suit the challenges of modern secular life

Sure, Epicureans focused on seeking pleasure – but they also did so much more.

Antonio Masiello/Getty Images
Culture & Religion

'The pursuit of Happiness' is a famous phrase in a famous document, the United States Declaration of Independence (1776). But few know that its author was inspired by an ancient Greek philosopher, Epicurus. Thomas Jefferson considered himself an Epicurean. He probably found the phrase in John Locke, who, like Thomas Hobbes, David Hume and Adam Smith, had also been influenced by Epicurus.

Nowadays, educated English-speaking urbanites might call you an epicure if you complain to a waiter about over-salted soup, and stoical if you don't. In the popular mind, an epicure fine-tunes pleasure, consuming beautifully, while a stoic lives a life of virtue, pleasure sublimated for good. But this doesn't do justice to Epicurus, who came closest of all the ancient philosophers to understanding the challenges of modern secular life.

Epicureanism competed with Stoicism to dominate Greek and Roman culture. Born in 341 BCE, only six years after Plato's death, Epicurus came of age at a good time to achieve influence. He was 18 when Alexander the Great died at the tail end of classical Greece – identified through its collection of independent city-states – and the emergence of the dynastic rule that spread across the Persian Empire. Zeno, who founded Stoicism in Cyprus and later taught it in Athens, lived during the same period. Later, the Roman Stoic Seneca both critiqued Epicurus and quoted him favourably.

Today, these two great contesting philosophies of ancient times have been reduced to attitudes about comfort and pleasure – will you send back the soup or not? That very misunderstanding tells me that Epicurean ideas won, hands down, though bowdlerised, without the full logic of the philosophy. Epicureans were concerned with how people felt. The Stoics focused on a hierarchy of value. If the Stoics had won, stoical would now mean noble and an epicure would be trivial.

Epicureans did focus on seeking pleasure – but they did so much more. They talked as much about reducing pain – and even more about being rational. They were interested in intelligent living, an idea that has evolved in our day to mean knowledgeable consumption. But equating knowing what will make you happiest with knowing the best wine means Epicurus is misunderstood.

The rationality he wedded to democracy relied on science. We now know Epicurus mainly through a poem, De rerum natura, or 'On the Nature of Things', a 7,400 line exposition by the Roman philosopher Lucretius, who lived c250 years after Epicurus. The poem was circulated only among a small number of people of letters until it was said to be rediscovered in the 15th century, when it radically challenged Christianity.

Its principles read as astonishingly modern, down to the physics. In six books, Lucretius states that everything is made of invisible particles, space and time are infinite, nature is an endless experiment, human society began as a battle to survive, there is no afterlife, religions are cruel delusions, and the universe has no clear purpose. The world is material – with a smidgen of free will. How should we live? Rationally, by dropping illusion. False ideas largely make us unhappy. If we minimise the pain they cause, we maximise our pleasure.

Secular moderns are so Epicurean that we might not hear this thunderclap. He didn't stress perfectionism or fine discriminations in pleasure – sending back the soup. He understood what the Buddhists call samsara, the suffering of endless craving. Pleasures are poisoned when we require that they do not end. So, for example, it is natural to enjoy sex, but sex will make you unhappy if you hope to possess your lover for all time.

Epicurus also seems uncannily modern in his attitude to parenting. Children are likely to bring at least as much pain as pleasure, he noted, so you might want to skip it. Modern couples who choose to be 'child-free' fit within the largely Epicurean culture we have today. Does it make sense to tell people to pursue their happiness and then expect them to take on decades of responsibility for other humans? Well, maybe, if you seek meaning. Our idea of meaning is something like the virtue embraced by the Stoics, who claimed it would bring you happiness.

Both the Stoics and the Epicureans understood that some good things are better than others. Thus you necessarily run into choices, and the need to forgo one good to protect or gain another. When you make those choices wisely, you'll be happier. But the Stoics think you'll be acting in line with a grand plan by a just grand designer, and the Epicureans don't.

As secular moderns, we pursue short-term happiness and achieve deeper pleasure in work well done. We seek the esteem of peers. It all makes sense in the light of science, which has documented that happiness for most of us arises from social ties – not the perfect rose garden or a closet of haute couture. Epicurus would not only appreciate the science, but was a big fan of friendship.

The Stoics and Epicureans diverge when it comes to politics. Epicurus thought politics brought only frustration. The Stoics believed that you should engage in politics as virtuously as you can. Here in the US where I live, half the country refrains from voting in non-presidential years, which seems Epicurean at heart.

Yet Epicurus was a democrat. In a garden on the outskirts of Athens, he set up a school scandalously open to women and slaves – a practice that his contemporaries saw as proof of his depravity. When Jefferson advocated education for American slaves, he might have had Epicurus in mind.

I imagine Epicurus would see far more consumption than necessary in my own American life and too little self-discipline. Above all, he wanted us to take responsibility for our choices. Here he is in his Letter to Menoeceus:

For it is not drinking bouts and continuous partying and enjoying boys and women, or consuming fish and the other dainties of an extravagant table, which produce the pleasant life, but sober calculation which searches out the reasons for every choice and avoidance and drives out the opinions which are the source of the greatest turmoil for men's souls.

Do you see the 'pursuit of happiness' as a tough research project and kick yourself when you're glum? You're Epicurean. We think of the Stoics as tougher, but they provided the comfort of faith. Accept your fate, they said. Epicurus said: It's a mess. Be smarter than the rest of them. How modern can you get?Aeon counter – do not remove

This article was originally published at Aeon and has been republished under Creative Commons. Read the original article.


NASA's idea for making food from thin air just became a reality — it could feed billions

Here's why you might eat greenhouse gases in the future.

Jordane Mathieu on Unsplash
Technology & Innovation
  • The company's protein powder, "Solein," is similar in form and taste to wheat flour.
  • Based on a concept developed by NASA, the product has wide potential as a carbon-neutral source of protein.
  • The man-made "meat" industry just got even more interesting.
Keep reading Show less

Where the evidence of fake news is really hiding

When it comes to sniffing out whether a source is credible or not, even journalists can sometimes take the wrong approach.

Sponsored by Charles Koch Foundation
  • We all think that we're competent consumers of news media, but the research shows that even journalists struggle with identifying fact from fiction.
  • When judging whether a piece of media is true or not, most of us focus too much on the source itself. Knowledge has a context, and it's important to look at that context when trying to validate a source.
  • The opinions expressed in this video do not necessarily reflect the views of the Charles Koch Foundation, which encourages the expression of diverse viewpoints within a culture of civil discourse and mutual respect.
Keep reading Show less