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Biodiversity Blog

 

Pets as Invasive Species: Amphibians and Reptiles

BurmesePython
Burmese python. (Photo: Susan Jewell, US Fish and Wildlife Service, CC)

In the pet trade, amphibians and reptiles are considered “exotic.” They and other species like certain fish and birds for example also share the same label. There is such a demand for exotics that the industry around them is a multi-billion dollar global business. That’s a lot of exotic pets and pet supplies.

However, the exotic pet trade is among the primary causes of the spread of invasive species, according to a 2019 academic review in Frontiers in Ecology and the Environment. This review found that the exotic pet trade leads to the establishment of hundreds of invasive species.

As touched on in our intro blog on invasive pets, invasive species wreak havoc. Environmentally, they are the second largest reason for biodiversity loss. Economically, their damage adds up to the tune of over a trillion dollars in the global economy. In this blog, we will be looking at just a few of the invasive pet amphibians and reptiles out there, as well as what some are trying to do about it.

Let’s start with the Burmese python (Python bivittatus), native to South Asia. They average about 16 feet (4.88 meters) in their native habitat. Their large sizes make them unwieldy, and pet owners sometimes release them into the wild, usually unaware of the amount of damage they can do.

Here in the US, established populations are currently in south Florida, near marshes, swamps, and other freshwater sources. Florida is a central location for the exotic pet trade, and happens to also be an invasive species hot spot. The Burmese python is one of the most concerning invasive species in the Everglades National Park where they are responsible for the decline of several mammal species. The numbers are particularly striking in the remote southernmost regions of the Everglades, where these pythons have been established the longest. In a 2012 study of the area, populations of raccoons had dropped 99.3 percent, opossums 98.9 percent, and bobcats 87.5 percent since 1997. Marsh rabbits, cottontail rabbits, and foxes effectively disappeared. Some species threatened by the python are endangered (such as the Key Largo woodrat, Neotoma floridana smalli) and the indigo snake (Drymarchon couperi).

Currently, there are groups like Python Patrol that are trying to keep the python under control. Nature Conservancy Florida launched Python Patrol in the Florida Keys in 2008 and, with the help of Everglades National Park, expanded the effort to the mainland in 2010. The responders trained by the Conservancy safely and humanely capture and remove pythons or other exotic constrictors they encounter. If you happen to be in Florida and spot a Burmese python, you can report it using the free IveGot1 app, online at IveGot1.org. They also provide a phone number to use if the animal is immediately visible: 1-888-IVEGOT1.

African clawed frog
 African clawed frog. (Photo: Brian Gratwicke - Creative Commons Attribution 2.0 Generic license)

There are also some rather fascinating studies involving putting radios in snakes and tracking them to unradioed mates, which are then removed from the gene pool.

There was also the 2013 Python Challenge, a month-long contest where 68 pythons were removed. The contest offered prizes for the longest and greatest number of captured pythons, while also raising awareness of invasive species.

Another invasive pet that is much smaller than the Burmese python is the African clawed frog (Xenopus laevis). They are native to sub-Saharan Africa and are currently considered invasives on four continents. They are the standard experimental amphibian used in research labs, but also sometimes as pets because of their quirky appearance. However, they are highly adaptable and can live in many types of water sources. They are voracious eaters, like many invasives. They eat just about anything, dead or alive, and sometimes their own tadpoles. As a result, they out compete native species. Outside of this destructive appetite, African clawed frogs carry chytrid fungus, which causes the potentially-fatal skin disease in frogs called chytridiomycosis. It’s believed that chytridiomycosis is a leading cause of the decline of native amphibian populations all over the world and responsible for the extinction of over 100 species since the 1970s. African clawed frogs also secrete skin toxins that may be harmful to predators, including native fish and other aquatic species.

How about pet lizards? Beyond the Burmese python, Florida is also dealing with the Argentinian black-and-white tegu (Salvator merianae). Despite being as large as dogs, they are docile and intelligent, making them sought-after pets. However, like many invasives, they are indiscriminate omnivores, posing threats to several endangered species like the Eastern indigo snake and gopher turtles. Other southeastern states are starting to see populations of this lizard appear, those states being South Carolina, Alabama, Louisiana, and here in our own state of Texas. They are hardy, which allows them to tolerate temperatures usually too harsh for other lizards. With the warming brought on by climate change, their range is likely to spread.

Tegu
 Black and white Tegu. (Photo: Chucao - Creative Commons Attribution-Share Alike 3.0 Unported license.)

Some states are attempting to curb the spread of the tegu. Georgia practices trapping and raising public awareness. The Georgia Reptile Society has a Tegu Task Force. Residents can submit photos of suspected tegus for identification. Once a tegu is identified, the society’s volunteers trap the animal and bring it to a rescue facility. They are then given to people who want them as pets. Alabama has enacted laws baring the import of the tegu.

These above species are ones with native habitats outside of the US that have come in via the international pet trade. However, there are other pets with native habitats inside the US that have become invasive in other areas, both here and across the world. Two such species are American bullfrogs (Rana catesbeiana) and Red-eared sliders (Trachemys scripta elegans).

The American bullfrog is very adaptable and prolific. It has a voracious appetite. The young can have a significant and negative impact upon benthic algae, the basis for many food webs. This species also contributes to the spread of pathogens such as the chytrid fungus, Batrachochytrium dendrobatidis.

The Red-eared slider should be an animal we here at UT are very familiar with. It’s the turtle that inhabits the turtle pond, and as our article on it explains, it has been the most popular turtle in the pet trade across the world. Still, little is known of its ecological impact, but their omnivorous diet and adaptability could give them potential for impacting many indigenous habitats.

Check out our other blogs on pets as invasive species! Start here with the intro. Then read any of these: Fish Gone Wild, the blog on cats, dogs, and birds.

Thanks to Travis Laduc, Curator in the Herpetology Collection, for his edits to this piece.

 

frog and turtle
 American bullfrog (left) and red-eared slider (right). (Frog photo: Carl D. Howe - Creative Commons Attribution-Share Alike 2.5 Generic license. Turtle photo: Nicole Elmer)

SOURCES

“African Clawed Frog.” Smithsonian’s National Zoo & Conservation Biology Institute.” (https://nationalzoo.si.edu/animals/african-clawed-frog)

“California’s Invaders: African clawed frog” California Department of Fish and Wildlife. (https://wildlife.ca.gov/Conservation/Invasives/Species/Clawed-Frog)

“How have invasive pythons impacted Florida ecosystems.” United States Geological Survey. (https://www.usgs.gov/faqs/how-have-invasive-pythons-impacted-florida-ecosystems)

“Python Patrol: Stopping a Burmese Python Invasion.” Nature Conservancy. October 14, 2019 (https://www.nature.org/en-us/about-us/where-we-work/united-states/florida/stories-in-florida/stopping-a-burmese-python-invasion/)

Rana catesbeiana (American bullfrog). CABI Invasive Species Compendium. (https://www.cabi.org/isc/datasheet/66618#tosummaryOfInvasiveness)

Renner, Rebecca. “This dog-sized lizard is spreading through the southeastern U.S.” National Geographic, November 18, 2020. (https://www.nationalgeographic.com/animals/article/tegu-lizards-invasive-spreading-southeast-united-states)

Roth, Annie. “Why you should never release exotic pets into the wild.” National Geographic, July 3, 2019. (https://www.nationalgeographic.com/animals/article/exotic-pets-become-invasive-species)

Trachemys scripta elegans (red-eared slider). CABI Invasive Species Compendium. (https://www.cabi.org/isc/datasheet/61560)

USDA National Invasive Species Information Center: Burmese Python. (https://www.invasivespeciesinfo.gov/terrestrial/vertebrates/burmese-python)

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