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[homepage] INVASIVE SPECIES Non-native, invasive species of plants and animals are a huge problem for the United States. With impacts on the environment, the economy, and human health, it is estimated the cost of invasives is over $138 billion a year. It is estimated that over 50,000 non-native species of plants and animals have been released into the United States. There are many different reasons animals get released ranging from accidental, biotic enhancement, and pest control. Upon recognition of this problem the federal government implemented the National Invasive Species Act of 1996 [http://thomas.loc.gov/cgibin/query/z?c104:H.R.4283.ENR:] to try and manage invasive species. The Fort Collins Science Center [www.fort.usgs.gov] has an Invasive Species Science Branch [www.fort.usgs.gov/ISS/] that provides research and technical assistance to invasive species management concerns. They are developing the Invasive Species Information Node of the National Biological Information Infrastructure (NBII) [http://invasivespecies.nbii.gov], which is a comprehensive, web-accessible database of invasive plant and animal species and disease agents. They have also teamed up with Colorado State University [www.colostate.edu], NASA [http://nasascience.nasa.gov/about-us] and other organizations to construct models to better understand and predict invasive species behavior. [link to Invasive Reptiles] INVASIVE REPTILES There are at least 53 invasive species of reptiles in the United States, the majority being in Florida and Hawaii. One of the most problematic invasive reptiles, however, has been in Guam. The Brown Tree Snake [http://www.fort.usgs.gov/resources/education/bts/bioeco/btsnake.asp] was accidentally let into Guam and is responsible for eradicating nearly all native bird species and most of the bats and lizards on Guam. Its damages total 1 to 4 million dollars per year. It is frequently the cause of power outages. This snake also poses a threat to humans as it can be aggressive when threatened and is venomous. Picture: It is estimated that up to 13,000 snakes per square mile occur in some forested areas in Guam In the 1950’s the South American Cane toad was introduced to control sugar cane pests. Now it preys and competes with native species and is highly toxic to predators. Recently, Florida has been having problems with invasive snakes. Giant constrictors, believe to have been released by pet owners, are establishing themselves in the Everglades National Park. [www.nps.gov/ever/] There are concerns for the threatened and endangered wildlife that reside in the park as well as the possible spread of these snakes to other parts of Florida and other areas of the United States. [link to Burmese python page] THE BASIC BIOLOGY OF THE BURMESE PYTHON The Burmese python, Python molurus bivittatus, is a subspecies of the Indian python. Recently this python has established itself as an invasive species in southern Florida. A viable population has inhabited Everglades National Park [www.nps.gov/ever/], and the species continues to expand its range outside the park. This population is thought to have resulted from the illegal release of unwanted pets. There is now concern over the spread of this species through much of Florida and possibly to other parts of the United States. NATIVE RANGE AND HABITAT: The Burmese python is native to India, Burma, Indonesia, Vietnam, southern China, and parts of Thailand. The species is reported to be declining or rare over some of this range. Climate may be a factor that limits the python’s distribution. The western edge of this range follows deserts and relatively dry areas, showing that aridity is likely the limiting condition of its western habitat. The southern and eastern limits follow the coast of Asia although it has a disjunctive range in Indonesia and Malaysia. The northern limits of the python’s reach are met by the high altitude, high latitude and cold temperatures of the Himalayan Mountains and by cold areas in lower elevations in China. The Burmese python is found in a number of different habitats and is considered to be a habitat generalist. It can inhabit estuarine mangrove forests, marshes, swamps, arid scrub jungles, rainforests, river valleys, grasslands, and rocky foothills. They do make use of larger undisturbed areas to hunt and hide in but are also present in human occupied areas. Pythons have been spotted in rocky clefts and caves, abandoned mammal burrows, hollow trees, dense water reeds, drainage pipes, and mangrove thickets. Pythons are also very good climbers and juveniles are often spotted in trees. A permanent water source is beneficial to these snakes. Pythons are quite at home in the water and are often times considered semi-aquatic. They are excellent swimmers and can hold their breath for at least 30 minutes. The water is often a suitable means for foraging and hunting. Pythons can be both nocturnal and diurnal. This can depend largely on the time of the year. They appear to be diurnal from October through April and primarily nocturnal from June through August in their native range. TO EAT OR BE EATEN: In addition to being a habitat generalist, the python is considered to be a generalist predator. It will prey on a number of different animals. It is known to feed on mammals, birds, reptiles including monitor lizards and, occasionally, other snakes. In some cases it was reported that insects and some fruits were found in the stomachs of the python. Adults chiefly prey on large mammals and birds to a lesser extent. One record has shown that an 18 foot long python killed and ate a four foot long leopard. Predation of humans is rare but a few reports of attacks have surfaced. Many of these cases were from pet snakes in the United States. Pythons are, however, quite capable of killing an adult human. Children are at an even greater risk of attacks. Burmese pythons use a number of different tactics to find food. They have the ability to ambush their prey. They make use of this “lie in wait” approach as well as actively forage for food. They are a powerful constrictor and use this to overcome their prey. There are a few natural predators of the python. In its native range, otters and tigers are known to kill pythons. Diseases such as tuberculosis, ticks, and other parasites have been known to infect these snakes. In Florida potential predators include alligators, the American crocodile, eastern indigo snakes, turtles, raptors, and medium to large sized mammals. Automobiles, farm equipment, and lawnmowers also kill significant numbers of Burmese pythons in Florida. REPRODUCTION, DEVELOPMENT, AND SIZE OF THE PYTHON: Burmese pythons become sexually mature at around 2-3 years old in their native range. Copulation normally occurs during hibernation and cooler times of the year. In Florida they have been found breeding in the open swamps and on levees. There have been reports of mating balls forming, where a number of males are found with one large female. Females have the ability to store sperm until conditions are ideal to lay eggs. The typical number of eggs laid by a python is 15-54 (average 30), but up to 107 have been recorded. Hatching occurs after 2-3 months. The female python will remain with the eggs and will not feed during this time. The females incubate the eggs, and by shivering are capable of raising their body temperature 6-8° C to aide in the incubation. This gives the snake the ability to reproduce in a more temperate climate than other snakes. Hatchlings measure 43-79 cm and can grow extremely quickly. They have the potential of growing 170% in the first year. Female pythons generally grow longer than males (typically 5-6 feet longer). They have the potential to grow to great lengths (5.8-7 m) and up to 91 kg in weight. In captivity, pythons have been known to live for over 30 years (their longevity in the wild is unknown). FLORIDA’S POPULATION OF PYTHONS: Reports of Burmese python sightings are growing in Florida, especially in Everglades National Park. [www.nps.gov/ever/] Recently they have been spotted in Collier-Seminole State Park [www.floridastateparks.org/collier-seminole/] and Big Cypress National Preserve. [www.nps.gov/bicy/] Many of these sightings were on roads, road shoulders, slopes of canal levees and other higher grounds where they are easily visible to humans on foot. However, radio telemetry has shown that snakes are in no way dependent on these human-altered areas, and some observations were made in remote areas such as mangrove creeks, creek banks and marshes. From 1979 to July 2005, there were 248 python observations recorded. The numbers of observations has increased dramatically in the Everglades National Park [www.nps.gov/ever/] since 2001. In 2007 alone, 250 pythons were found in the park. They are now being recorded farther north and east. Officials suspect that most of the Burmese python introductions were unwanted pets that became too large to handle and were released illegally into the park. As evidenced by the discovery of large numbers of juveniles and several females brooding eggs, Burmese pythons are reproducing in southern Florida. Authorities suspect that the population is large and increasing in the Florida Everglades and has the potential to spread from this area. Pythons have the potential to become an important predator on native wildlife populations in Florida, having the ability to cause harm to the ecosystem. They will compete for the same prey as alligators and indigo snakes but will become prey to these animals as well. [link to Species at Risk] [link to Risk Assessment] [link to Related Resources] (my bibliography) SPECIES IN FLORIDA AT RISK TO THE BURMESE PYTHON The Everglades National Park [www.nps.gov/ever/] is home to many threatened and endangered animals. In many instances, this is the only remaining habitat where the species is found. There are 16 species listed as endangered and 6 species listed as threatened in the Everglades. The following is a list of vertebrates most likely to be impacted by an established population of boas or pythons. This list was compiled by comparing the geographical ranges of these animals and where the pythons are believed to have inhabited. Lower Keys Marsh Rabbit, Sylvilagus palustris hefneri: This rabbit is listed as endangered and its range is limited to the Florida Keys. Its habitat is similar to the python’s habitat: salt or freshwater marshes, mangroves and shrubby edges of wetlands. Florida Mastiff Bat, Eumops glaucinus floridanus: This bat is listed as endangered by the state of Florida. Its range is limited to the southern tip of Florida where the python has been found. This bat would be especially vulnerable to juvenile pythons. Snail Kite, Rostrhamus sociabilis plumbeus: This Falcon is listed as endangered. Its range overlaps with what is expected of the python. It is dependent upon the same habitat for hunting as the python. Key Largo Woodrat, Neotoma floridana smalli: Also listed as endangered, this woodrat is susceptible to predation throughout its natural range. Cape Sable Seaside Sparrow, Ammodramus maritimus mirabilis: This bird is listed as endangered and only found on the southern tip of Florida. It is a permanent resident of the freshwater interior marshes of the Everglades. Key Deer, Odocoileus virginianus clavium: This endangered small deer resides in the Florida Keys. Its habitat is similar to the python, and it could easily be taken down by an adult python. There are also a few listed species that could suffer because of competition for food and habitat with pythons and boas. American Crocodile, Crocodylus acutus: Found only in the southern portion of Florida, these reptiles are listed as endangered. They share a common habitat with the python and would be in direct competition for food and space. There is also a large threat of predation upon juvenile crocodiles. Eastern Indigo Snake, Drymarchon corais couperi: Currently listed as threatened, this species’ geographic range is throughout the southeastern United States. This snake could easily be impacted by the presence of the python because of the shared habitat and competition for prey. There is also the threat of exposure to different pathogens from the introduced pythons. This is just a brief list of threatened and endangered wildlife that could be affected by a viable population of Burmese pythons and other constrictor snakes. For more threatened or endangered species at risk visit [www.fnai.org] or [www.floridainvaders.org]. A BRIEF RISK ASSESSMENT OF THE BURMESE PYTHON IN FLORIDA The Fort Collins Science Center [www.fort.usgs.gov] is looking into the potential impacts of introduced snakes to Florida as well as the rest of the United States. There are different species of giant constrictor snakes that have the potential to alter the community of life in the Everglades National Park [www.nps.gov/ever/] as well as other parts of the southern United States. The most common of these snakes is the Burmese python (Python molurus bivittatus). Several hundreds of these pythons have been collected from The Everglades. The other species include: Python reticulatus, Boa constrictor, Eunectes murinus, Python sebae, Python natalensis, Eunectes notaeus, Eunectes beniensis, and Eunectes deschauenseei. In 2006 the South Florida Water Management District petitioned the US Fish and Wildlife Service to add many of these giant constrictors to the list of Injurious Wildlife. This list limits private ownership of these snakes. Other regulatory actions have also been taken or proposed to combat this issue of invasive snakes. In 2006 the Florida Wildlife Commission proposed that private ownership be regulated. This could be done by tagging pet snakes to facilitate tracking of lost or released individuals. At this time the USGS has proposed a risk assessment to look at the potential impact of these snakes. They plan to conduct comprehensive literature reviews to gather information for each of the above snake species. Using this information, they will project which animals are likely to fall prey to these snakes. In February 2008, the USGS released its findings from a study looking at “What parts of the US mainland are climatically suitable for invasive alien pythons spreading from Everglades National Park” [link to study and/or news release]. It projects that the Burmese python could find “comfortable climatic conditions” in close to a third of the United States, mostly in the south. This study looked at the climate of the python’s native range in Asia and matched it to that of the United States. It takes into account rainfall and temperature statistics of an area including Pakistan east to China and south to Indonesia. The climatically matched areas of the United States “ranged up the coasts and across the south from Delaware to Oregon, and included most of California, Texas, Oklahoma, Arkansas, Louisiana, Mississippi, Alabama, Florida, Georgia, and South and North Carolina.” Present Climate suitability Also in this study the USGS projected the distribution of the python by the year 2100 to be even larger when looking at predicted climate maps. These projections “extend northward beyond the current limit to include parts of the states of Washington, Colorado, Illinois, Indiana, Ohio, West Virginia, Pennsylvania, New Jersey, and New York.” Year 2100 projected climate suitability based on global warming models. The USGS and Everglades National Park [www.nps.gov/ever/] are looking more into the requirements for the survival of the Burmese python. They are hoping to be able to predict where these snakes are going and if they will develop into a viable population. The USGS is exploring other risks of this invasive species such as their potential for social, economic, and other environmental impacts. Both agencies are also looking into developing tools to control these snake populations and/or prevent their spread. These climate maps showing the potential range of the Burmese python along with the basic biology of the snake demonstrates the urgency for action. These snakes have the ability to cause a lot of damage to the Everglades ecosystem as well as to a good portion of the southern United States.