Pythons, People & Pathways: Invasive Species Slither In

[picture of python taken by author on visit by National Invasive Species Advisory Committee - ISAC to the Everglades]


I was asked how the Burmese pythons that now inhabit the Florida Everglades as an invasive species arrive. I quickly answered that it was not by first class reservation on a commercial airline, but rather from the pet industry. Pet industry though does not mean just the business operations but includes the customers for whom they procure a wide variety of pets. This is an important part of the discussion for it is often too easy to blame just the business side of the issue. No business lasts long that does not provide a product sought by its consumer market.

The website, Everglades Burmese Python Project, describes the south Florida ecosystem invader as a”… Burmese python (Python molurus bivittatus) are large, constricting snakes, native to southeastern Asia, that are one of the most popular snakes in the pet trade.”[1] Popular means that there are many customers who think that having a python is the sine qua non of their existence, a personal necessity for their own quality of life. And the American consumer the bulwark of the global economy is not to be denied his want. As with many wants, though, the unexpected consequence of a good python owning regime is a 15 foot pet. Not unexpectedly, the cost of containment and subsistence grows with the snake leading a few owners to decide, much like gardeners heavy clipping of ivy over the fence into a park, that the snake deserves the best and nature is boundless and unlimited in her abilities to care for the now burdensome former trophy. Out of the bag and into the Everglades and the Florida canal system the soon to be lost love slithers.

EPA provides a list of invasive species pathways noting that ‘[e]scapes or intentional release of unwanted pets can be a source of new non-native species in all parts of the country.” [2] It is most likely the case that the customers are releasing the invasive species intentionally or not rather than the businesses throwing away costly inventory. Disposal of possessions non longer wanted or needed is a challenge. The idea that the land is infinite and that we can just bury our problems is becoming a costly solution, as is releasing our pets into nature out of an anthropocentric sense of kindness. Everything has a consequence even refuse and trash, unwanted plants and pets, and those cherished species that escape from out gardens and homes.

Invasive species negatively impact every one of our current ecosystem services altering the resources that the system provides. Invasive species which are top predators may expand rapidly, deplete resources and may fade away or may become established, altering the known ability of the system to create benefits for humanity. Invasive species introduction in effect create new ecosystems that are restructuring and resetting ecological interactions and while doing so creating challenges for resource predictability. Some invasive species in certain settings can enhance ecosystem services such as Miscanthus sinensis used for erosion control.[3] These diametrically opposed possibilities in part create the wicked inconvenience of invasive species and the issues that surround them




[1] Dr. Michael Dorcas. Davidson College Herpetology Laboratory http://www.bio.davidson.edu/people/midorcas/research/StResearch/Python%20Project%20Website/Python.htm
Dr. Michael Dorcas and the Davidson College Herpetology laboratory are assisting the National Park Service, Dr. Frank Mazzotti, and his laboratory in their studies of Burmese Pythons in Everglades National Park and surrounding areas. Burmese Pythons (Python molurus bivittatus) are large, constricting snakes, native to southeastern Asia, that are one of the most popular snakes in the pet trade. Unfortunately, most pet owners do not realize that their 3 foot, hatchling python may grow to be longer than 15 feet. At this point, owners are frequently unable to care for such a large snake and release them. Researchers believe this is the initial reason for the population of Burmese Pythons in the Everglades; however, over time these captive snakes have bred in the Park and now there appears to be a well-established population. These snakes thrive in the Everglades because they are habitat generalists and the park has an abundance of prey available to them (nearly any animal that exists in the Everglades). These snakes have the ability to consume large animals and potentially pose a threat to threatened and endangered populations of Florida Panthers and Wood Storks among others in the Everglades. Thus, researchers are studying these animals to discover the best ways to eradicate or control the Burmese Python population. Researchers are conducting road surveys to capture snakes and are radio-tracking pythons in the area. Their goal is to determine how Burmese Pythons are using the habitat available to them in Everglades National Park and document the impact the snakes are having on native animal populations. We have been assisting with this project by conducting surgeries to implant transmitters and temperature dataloggers, aiding data collection along roads, and assisting with GIS analysis
[2] Pathways for Invasive Species Introduction http://www.epa.gov/owow/invasive_species/pathways.html Globalization has vastly increased long-distance travel and commerce, and highly altered waterways. These and other factors have increased the frequency by orders of magnitude by which non-native plants, animals and pathogens are introduced to new areas, sometimes with costly results. Invasive species can enter important aquatic habitats including riparian zones and wetlands by several common pathways listed below.
Ballast Water: Since 95% of all foreign goods by weight enter the U.S. through its ports, the potential for invasive species impacts on coastal communities is immense.
Boat Hulls, Fishing Gear and Other Recreational Pathways: Boat hulls, fishing boots (felt-soled wading boots transport whirling disease organisms from stream to stream) and equipment, diving gear, and other recreational items that are transported among several water bodies have been known to spread invasive species problems to new waters. Some zebra mussels and milfoil have been introduced via these pathways.
Aquaculture Escapes: Non-native shrimp, oysters and Atlantic salmon in the Pacific Northwest, are just a few examples of non-native mariculture species that have generated concern over disease and other impacts that might arise from their escape.
Intentional Introductions: The introduction of non-indigenous species into ecosystems with few controls on reproduction or distribution.
Aquaria Releases: Escapes or intentional release of unwanted pets can be a source of new non-native species in all parts of the country. The invasive algae Caulerpa is thought to have been introduced to U.S. waterways after being discarded from aquaria.
Live Food Industry: The import of live, exotic foods and the release of those organisms can result in significant control costs, e.g. the snakehead fish in Maryland. Asian swamp eels are spreading through the Southeast after introduction as a food source.
Vehicular Transportation: Both private and commercial transportation are major factors in the movement and range expansion of non-native species throughout the U.S.
Escaped Ornamental Plants, Nurseries Sales, or Disposals: Many invasive plant problems began as ornamental plantings for sale in nurseries and garden shops. Purple loosestrife, for example, is sold as an ornamental plant but takes over native vegetation in wetlands, and can clog western streams preventing water withdrawal and recreational uses. Only some problem species are currently banned from sale.
Cross-basin Connections: From small channels to major intercoastal waterways, new connections between isolated water bodies have allowed the spread of many invasive species. Great Lakes invasions increased markedly after the opening of the St. Lawrence Seaway in 1959.
Fishing Bait Releases: Discarding unused bait can introduce species that disrupt their new ecosystems and eliminate competing native species; examples include non-native crayfish, baitfish that overpopulate certain waters, and earthworms that are depleting the organic duff layer in northern forests where no indigenous earthworms existed (Conover, 2000).
Illegal Stockings: Although prohibited by law, people release fish into new waters and sometimes cause severe impacts. Yellowstone Lake's world-class cutthroat trout fishery is now jeopardized by an illegal release of lake trout.
Domestic Animals Gone Feral: The impact of feral house cats on birds and small mammals in natural areas is well documented; escaped feral pigs from farms have recently begun to do significant damage to soils and plants in the Smokey Mountains.
Pathogens Spread by Non-natives to Vulnerable Native Species: Non-native species problems include pathogens carried by resistant non-natives to vulnerable native species. Whirling disease, which has decimated rainbow trout in many western rivers, was originally introduced when European brown trout, tolerant of whirling disease, were imported to U.S. waters and hatcheries.
Disposal of Solid Waste or Wastewater: Seeds, viable roots or other propagules of invasive plants may be easily spread to receiving waters through wastewater discharge, then spread by water flow to distant areas downstream.
Science/laboratory Escapes, Disposals or Introductions: Accidental or intentional release of laboratory animals has introduced some non-native species into U .S. waters.
Seafood Packing and Disposal: Much seafood is packed in seaweed prior to distribution. Because seafood is transported long distances, organisms in packing seaweed may reach new waters as an unintended by-product.
Biological Control Introductions: Ideally, introducing a second non-native species to control an invader should result in diminished numbers of both species after control is accomplished, but some introduced controls have backfired because they attack non-target species. Mongoose introduced in Hawaii to control rats have wiped out many native bird species.
Past Government Programs: The establishment of a new invader is sometimes an unanticipated outcome of a government program; kudzu, for example, was originally introduced through a government-sponsored erosion control program.
Moving and Depositing Fill in Wetlands: Seeds and viable parts of invasive plants contained in fill material may rapidly colonize the new substrate, which then compete with native species within the wetlands.
Land/water Alterations That Help Spread Invaders: Many invaders are adept at rapid pioneering where soil has been disturbed or water levels or routes have been changed, leaving a temporary gap in occupation by native flora and fauna.

[3] Ann Perry. August 21, 2009. “A Hedge with an Edge for Erosion Control”. http://www.ars.usda.gov/news/docs.htm?docid=1261 One way farmers can preserve soil and protect water quality is by planting grass hedges to trap sediment that would otherwise be washed away by field runoff. Agricultural Research Service (ARS) scientists at the agency’s National Sedimentation Laboratory in Oxford, Miss., have calculated how much soil erosion these hedges prevent and verified predictions of the Revised Universal Soil Loss Equation version 2 (RUSLE2).