A helicopter conducting routine post-fire wildlife surveys in the Everglades singled out an unusual feature in the burned landscape. After three hours of scanning for damage, the crew noticed a dark, raised formation with straight edges rising from the gray, ash-covered marsh. Natural peat mounds typically have rounded contours, but this structure had angular lines suggesting deliberate construction. The crew photographed the site, logged its GPS coordinates, and noticed that the biologist on board had also picked up the location on a python tracking receiver.
The signal came from a collar on a female Burmese python used as a “Judas snake” by the removal program. The animal had moved to this raised feature two days before the fire reached its previous position. The observation raised questions for both the wildlife team and the archaeologists who later examined the site.
The fire, which burned approximately 25,000 acres of sawgrass after a lightning strike, had stripped away the dense vegetation that normally conceals the ground surface. In the weeks before new growth returned, the burn area briefly revealed the underlying terrain. What emerged was a set of raised earthen formations that did not appear on existing maps of the region.
Archaeologist Nathan Hill of Florida International University reviewed the helicopter images and organized a field team. Within hours of their first survey, they found fragments of freshwater snail shells, chipped stone flakes, and pieces of worked stone on the ash-covered soil. At the base of one structure they recovered small fragments of burnt pottery. Radiocarbon dating of shell material from the deeper layers returned dates between 3,000 and nearly 5,000 years old.
The shells belonged to apple snails, which die naturally in large numbers throughout the Everglades. In most of the marsh, their shells scatter thinly across the sediment. At these sites, however, the shells were densely packed in uniform layers, stacked meters thick through repeated deposition over many generations. This type of accumulation is known in archaeology as a midden, essentially a refuse heap built up by people discarding food waste in the same location over long periods.
The consistency and structure of the shell deposits indicate that humans deliberately occupied these spots over roughly five millennia. The older cultural layers sit below more recent occupation levels from the 18th and 19th centuries associated with the Seminole and Miccosukee peoples, whose historical connection to the region is well documented and legally recognized. But the deeper shell deposits point to a much longer human presence.
According to the interpretation supported by this data, many of the tree islands in this part of the Everglades are not entirely natural formations. They began as slight elevations in the marsh, gradually raised over centuries by the accumulation of everyday refuse. As shell piles grew, trees took root and their roots stabilized the mound. Higher ground became more valuable, people returned more often, and the structures continued to rise. Over four to five thousand years, these mounds reached heights of one to three meters above the surrounding marsh. Aerial surveys and ecological monitoring had long classified them as natural forested islands.
LiDAR surveys of the burn area detected additional raised formations that had not been previously identified. The same mapping technique used to reveal ancient cities beneath forest canopies in Central America and Southeast Asia showed that the Everglades site contained dozens of candidate features hidden under the dense sawgrass. Reanalysis of archived LiDAR data from other parts of the national park found more potential sites.
The discovery intersected with python management in a concrete way. Burmese pythons are cold-blooded animals that regulate their body temperature through their surroundings. The flat sawgrass marsh offers limited shelter during cold snaps that periodically affect South Florida. Raised shell mounds, with their dense packed shell material retaining heat and tree cover reducing temperature extremes, function as effective thermal refuges.
Mortality data from Florida cold spells in 2010 and 2020 supports this pattern. When winter temperatures dropped into the range that impairs snake mobility, mass die-offs occurred across open marshland while snakes located on raised features had notably higher survival rates. The raised mounds also remain dry during seasonal flooding and can retain vegetation when surrounding areas burn.
Researchers from the archaeological team and the python removal program met about six weeks after the fire to compare their respective datasets. The matching of LiDAR-identified shell mound locations against years of python encounter records produced a clear correlation: the raised archaeological features showed python encounter rates three to seven times higher than comparable flat marsh areas, after accounting for vegetation, water depth, and seasonal temperatures.
Field workers had already identified these locations as high-yield hunting spots through experience, often returning season after season because signal detection justified the effort. What they had not known was that these productive sites sat directly above shell deposits built by people who had occupied the same marsh long before the first Burmese python entered it.
The fire also altered movement patterns. Post-fire surveys showed that snakes tracked by Judas collars moved toward raised features and remained there for weeks. With the usual thermal cover removed from the surrounding flatlands, the mounds became concentration points. Removal teams operating in the burn zone reported the highest encounter rates per unit of effort recorded for that administrative unit.
Python removal coordinators now use the shell mound mapping to prioritize sites for Judas snake deployment and trap placement within the burn area and adjacent regions where LiDAR has identified additional candidate features.
The sequence emerged accidentally: a lightning fire exposed terrain during a dry season, a helicopter crew noticed straight edges in the ash, an archaeologist recognized the shell deposits, and a wildlife biologist saw a tracking signal pointing at a newly visible feature on an otherwise familiar map. The resulting mound map is now part of python management planning in the affected region.
