Houston ChandlerViews:
Increasing globalization has led to a truly astounding number of reptile and amphibian species being easily available for purchase as part of the massive reptile and amphibian pet trade. Take a trip to a reptile show or browse the internet and you can buy anything ranging from alligators to large tortoises to some of the most venomous snakes in the world, often with less hassle than adopting a dog or cat from the pound. There are many issues related to the worldwide reptile and amphibian pet trade, including shady characters (the book Stolen World is eye-opening), both illegal and legal collection of wild animals, spread of diseases, and the release (either directly or indirectly) of potentially invasive species. Despite the best intentions of many people, these issues have persisted for decades and continue to negatively impact wild herpetofaunal populations.
Florida supports more nonnative species of reptiles and amphibians than anywhere else in the world. The list of species with established populations is long, and the ecological harm that species like Burmese Pythons (Python bivittatus) are causing in the Everglades has been well-documented (McCleery et al. 2015). The pet trade is the primary culprit for most, if not all, of these introductions. Regardless of whether pets escape from outdoor enclosures or are intentionally released, it is often too late to remove an invasive species once it becomes apparent that it is a problem. A narrow window exists where an invasive species can potentially be eradicated through targeted management actions. After this period, populations can grow rapidly and expand into new areas (Wilson et al. 2011), forcing management actions to shift towards containment and limiting the negative effects on native ecosystems.
Georgia sits far enough north that it has been mostly spared of the worst invasive herpetofaunal species. A colder winter prevents many species from persisting long-term in Georgia, even if they were somehow able to make it into the state. The most prevalent nonnative species in Georgia are species such as Cuban Treefrogs (Osteopilus septentrionalis), Brown Anoles (Anolis sagrei), and Mediterranean Geckos (Hemidactylus turcicus), all of which are usually found near human development. The ecological effects of these species are likely small compared to some of the more destructive species found farther south. However, a new invader could soon change that.
Argentine Black and White Tegus (Salvator merianae) are large lizards native to Brazil, Paraguay, and Argentina in South America. In their native range, black and white tegus (hereafter tegus, although there are multiple tegu species) inhabit a variety of habitat types and elevations. Males can grow to lengths in excess of 4 feet, and large jaws facilitate the consumption of a variety of food sources, including invertebrates, fruit, seeds, eggs, and small vertebrates. An ability to live in a variety of habitat types, consume a wide variety of food sources, persist through relatively cold temperatures via brumation during the winter months (McEachern et al. 2015), and lay large clutches (35 eggs per year on average) makes tegus a prime candidate for a successful invader. Indeed, breeding populations of tegus have been established in multiple Florida counties for at least 10 years, with the number of individuals removed from the wild increasing over the years (Harvey and Mazzottti 2015). The establishment of these populations has been attributed to escaped or released pets, and numerous reports of tegus from across Florida indicate that these large lizards often find their way into the wild. Tegus are popular and a fairly common reptile in the pet trade because of their intelligence, large size, and long life span.
Until recently, concerns about established tegu populations were restricted entirely to southern Florida. However, in 2017 and 2018, the Georgia Department of Natural Resources (DNR) started receiving reports of tegus from Tattnall and Tombs counties. These repeated reports prompted natural resource managers to setup game cameras during 2018 in an attempt to conform tegu presence in the areas where they were being reported. Over several months three individuals were captured on game cameras, and it became clear that a potential problem was already underway. But could they survive the colder Georgia winter?
Targeted trapping for tegus was initiated near where individuals had been documented during the spring of 2019. It didn’t take long to establish that individuals had, in fact, survived the winter and were still present on the landscape. Six individuals were captured during the spring near a single burrow, highlighting the need to work quickly to address this issue. Tegus can be trapped alive by baiting Tomahawk (Havahart) traps with chicken eggs. Additional partners were included on the project to aid in trapping efforts, and sightings of tegus were requested from the public. Georgia Southern University has now taken over a majority of the trapping efforts near the original sightings, running approximately 75 traps continuously since mid-summer. In total, 11 tegus have been captured or confirmed dead in Georgia during 2019. This includes a large adult that was found near Valdosta, Georgia and apparently represents another unrelated case of an escaped or released pet. Trapping success has slowed during hot weather but occasional reports of tegus suggest that there are still individuals on the landscape. It is also possible that adults have already bred, which would dramatically increase the number of individuals in the wild. Overall, there are few signs that the effort to remove these animals from Georgia’s ecosystems won’t stretch into 2020 and beyond.
An established population of tegus in the heart of southern Georgia poses potentially dramatic consequences for native wildlife. In Florida, tegus have been documented eating alligator and turtle eggs, frogs and toads, lizards, snakes, turtles, and small mammals (Harvey and Mazzottti 2015; Mazzotti et al. 2015). Their preference for eggs makes them a potential predator of ground nesting birds (e.g., turkey and quail), and an ability to dig makes few reptile nests inaccessible. The main introduction sites are located within 50 miles of some of the best remaining Gopher Tortoise and Eastern Indigo Snake habitat and populations. Increased predation pressure from an alien invader would have a negative impact on both of these species of conservation concern. Overall, the introduction of such a large and voracious predator is a troubling development for Georgia’s native wildlife, and it will take a combined effort of many partners to stop the spread of invasive tegus before it becomes a widespread problem.
Efforts to trap and remove tegus will continue for the foreseeable future. Understanding the current distribution in Georgia is crucial to effectively implementing a trapping program. Any sightings of tegus in Georgia should be reported to the Georgia DNR. To report tegu sightings in Georgia, take a photo (if possible), note the location, and log the sighting at www.gainvasives.org/tegus or by contacting DNR at (478) 994-1438 or gainvasives@dnr.ga.gov.
Literature Cited
Harvey, Rebecca G., and Frank J. Mazzotti. 2015. The Argentine Black and White Tegu in South Florida: Population growth, spread, and containment. Institute of Food and Agricultural Sciences. IFAS Publication Number WEC-360. http://crocdoc.ifas.ufl.edu/publications/factsheets/tegufactsheet.pdf.
Mazzotti, F. J., M. McEachern, M. Rochford, R. N. Reed, J. K. Eckles, J. Vinci, J. Edwards, and J. Wasilewski. 2015. Tupinambis merianae as nest predators of crocodilians and turtles in Florida, USA. Biological Invasions 17:47–50.
McCleery, R. A., A. Sovie, R. N. Reed, M. W. Cunningham, M. E. Hunter, and K. M. Hart. 2015. Marsh rabbit mortalities tie pythons to the precipitous decline of mammals in the Everglades. Proceedings of the Royal Society B 282:20150120.
McEachern, M. A., A. A. Adams, P.E. Klug, L. A. Fitzgerald, and R. N. Reed. 2015. Brumation of introduced Black and White Tegus, Tupinambis merianae (Squamata: Teiidae), in southern Florida. Southeastern Naturalist 14:319–328.
Willson, J. D., M. E. Dorcas, R. W. Snow. 2011 Identifying plausible scenarios for the establishment of invasive Burmese pythons (Python molurus) in Southern Florida. Biological Invasions 13:1493–1504.
