Pythons are large constricting snakes. When introduced into new environments, these reptiles become invasive species, posing substantial threats to native ecosystems and raising ecological concerns about their geographical spread. This article explores the expansion of invasive python populations and factors influencing their northern reach.
Origin of Invasive Python Populations
The presence of invasive pythons in North America stems primarily from the introduction of Burmese pythons, scientifically known as Python bivittatus. These snakes, native to Southeast Asia, were initially brought into Florida during the 1970s as part of the exotic pet trade. Many owners, unprepared for the immense size these snakes can attain, often released them into the wild when they became too difficult to manage.
A significant event contributing to their establishment was Hurricane Andrew in 1992, which destroyed a python breeding facility and zoo, inadvertently releasing numerous snakes into the Everglades. Between 1996 and 2006, over 90,000 Burmese pythons were imported into the U.S., further exacerbating the issue. By the late 20th century, a breeding population was established in South Florida, officially recognized by 2000, creating the source for their subsequent spread.
Identifying the Northernmost Reach
The established breeding population of invasive pythons is largely confined to South Florida, primarily within the Everglades ecosystem. Their confirmed range extends from just south of Lake Okeechobee to Key Largo, and westward from Broward County to Collier County. While isolated sightings have occurred further north, these are generally considered to be transient individuals or escaped pets, rather than indicators of established breeding populations.
The northernmost point where pythons have been regularly observed is around Gasparilla Sound, south of Myakka, Florida. Occasional individual pythons have been reported in central Florida, like in Bard, but these occurrences are infrequent. Further north, there have been documented sightings in Georgia, with reports dating back to at least 2011, including a 12-foot Burmese python killed near Albany. A more recent instance in Walton County, Georgia, in 2020, also involved a python believed to be a released pet. Similarly, an albino python was captured in Prosperity, South Carolina, in August 2025, which authorities suspect was an escaped or released pet. However, no established invasive populations of Burmese pythons have been confirmed in South Carolina.
Climate and Habitat Factors
Burmese pythons are ectothermic animals, meaning they rely on external environmental warmth to regulate their body temperature. This physiological characteristic makes them particularly vulnerable to cold stress, with significant mortality rates, sometimes as high as 90%, observed during winter freezes. Studies indicate that these snakes cannot survive prolonged exposure to body temperatures below 5-10 °C. A notable cold snap in 2010, where temperatures remained below 10°C for 12 days, resulted in widespread python deaths.
Despite this, some survivors of cold weather events have shown evidence of genetic adaptations that may confer greater cold tolerance and metabolic flexibility, enabling them to seek shelter underground. For optimal function, Burmese pythons require warm and humid environments, ideally with basking spots reaching 32-35°C and humidity levels between 60-70%. They also depend on a consistent water source and are adept swimmers.
Their preferred habitats include:
Broad-leafed and low-flooded areas such as cypress, overstory, and coniferous forests
Grasslands
Marshes
Swamps
Rocky foothills
River valleys with open clearings
The subtropical climate and expansive wetlands of the Florida Everglades provide suitable conditions for their proliferation. However, the occurrence of cold extremes remains a significant limiting factor for their sustained northward expansion beyond South Florida.
Efforts to Monitor and Control Spread
Various initiatives are in place to monitor and control the spread of invasive pythons, particularly in Florida. Public reporting programs, such as the Invasive Species Hotline and the IveGot1 mobile app, encourage citizens to report python sightings. This public involvement supplements the efforts of trained python removal agents. The Florida Fish and Wildlife Conservation Commission (FWC) Python Action Team – Removing Invasive Constrictors (PATRIC) and the South Florida Water Management District (SFWMD) Python Elimination Program (PEP) employ qualified individuals to capture and remove these snakes. These programs offer incentives and have collectively removed over 23,500 pythons as of April 2025. The annual Florida Python Challenge further engages the public in removal efforts.
Research into detection technologies aids these efforts. Sentinel snakes, which are male pythons implanted with radio transmitters, are used to locate breeding females, which are otherwise hard to find. Environmental DNA (eDNA) detection methods, which analyze water or soil samples for snake genetic material, offer a way to confirm python presence even after they have left an area. Additionally, newer methods are being explored, such as using robot rabbits designed to lure pythons out of hiding for removal.