A Burmese python in Florida's Big Cypress National Preserve vomited up an entire white-tailed deer after temperatures in South Florida dipped below 50 degrees Fahrenheit (10 degrees Celsius) late last year, well below the cold-blooded creature's comfortable range.
While pythons are known to vomit their meals in cold laboratory settings, scientists had never caught the elusive snakes doing it in the wild — until now. The unusual observation, made in late November 2024, is described in a study published in July in the journal Ecology and Evolution.
Burmese pythons (Python bivittatus) have been an invasive species in Florida since the late 1970s. Despite this decades-long presence, they are largely understudied, and there are gaps in knowledge about the snakes' biology and how they interact with native species, such as deer.
Deer numbers are declining in the preserve, which is concerning because they form an important part of the diet of local predators, like Florida panthers (Puma concolor coryi). To learn more about how often snakes eat deer and how quickly they digest them, scientists at the preserve spent a year tracking the digestion of several large female pythons — those deemed most likely to eat a deer.
One snake under observation had a large lump in its stomach, indicating that it had eaten something deer-sized. Over the next several days, though, this lump did not appear to get any smaller.
After a cold night, when temperatures dipped to 48.9 F (9.4 C) in the preserve, scientists revisited the snake. They found it lump-free, swimming in the shallow water of a willow swamp near a minimally digested white-tailed deer (Odocoileus virginianus) that it had vomited up.
"They found her very empty, and they were able to smell a deer not far away and put two and two together," Sandfoss said.
Because snakes are cold-blooded, or ectothermic, they find it difficult to function in the cold. Their biological processes, including digestion, slow down until the temperature warms back up.
If the outdoor temperature gets too cold, a snake's meal can start decomposing in its stomach faster than the snake can digest it, causing bacteria to build up. The snake's response is to vomit to eliminate the bacteria. This can be an energy-intensive activity for an already hungry snake, but the snake in the study survived it.
Because the Burmese python is an invasive species in Florida, the snake's survival has complex implications, Sandfoss said. It missed one of the large meals it takes only a few times a year, so it might lack the energy to reproduce, which could help control the python population. Alternatively, the snake may kill another deer to make up the lost energy, further endangering the deer population native predators rely on.
"Deer in Big Cypress have been declining for several years, and we believe pythons to be a factor in that," lead author Travis Mangione, a biologist at the National Park Service (NPS), told Live Science. "Because this python survived the vomiting event, it will keep eating native wildlife."
Even as scientists work to understand how Burmese pythons' vomiting events affect the local ecosystem, observations of it in the wild hold valuable clues to how far this invasive species can spread within the United States. Temperature is a key limiting factor for the snakes' range, and the coldest temperature they can survive might be the coldest in which they can digest, Sandfoss said.
The new study fits within a larger, not-yet-released research project that's analyzing the full year of python feeding data. The scientists working on the project hope it will shed light on the basic biological process of digestion in Burmese pythons, which is still under-researched.
"Pythons have complicated biology, and we've never really dealt with an animal like this at this scale — this large, invasive ectotherm, terrestrial," Sandfoss said. "We're trying to figure all these things out."
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