U.S. Fish and Wildlife Service The Effect of Cold Weather On Large Constrictor

In the months since that unusual In a related study, Dorcas et al. (2010) cold-weather event, hundreds of adult relocated 10 Burmese pythons from Burmese pythons and more than 24 the to an outdoor research hatchlings were captured alive in setting in South Carolina in June 2009. . During The following January, the pythons all 2010, 322 Burmese pythons were died. However, the pythons had not captured or removed from Everglades had a chance to acclimate to a milder National Park and vicinity, of which winter before they were exposed to 67 were removed from October 18 to temperatures that were “appreciably December 31, 2010—many months colder than typical winters in South after the cold spell ended. The 322 Carolina.” Dorcas et al. (2010) Burmese pythons found in 2010 concluded: “Some pythons in our study represent only a 12 percent reduction were able to withstand long periods from numbers removed in 2009 (367 of considerably colder weather than is total). The freeze appears to have had a typical for South , suggesting greater effect on pythons in the shallow that some snakes currently inhabiting marsh habitats, where underground Florida could survive typical winters and deep water refuge was absent. in areas of the southeastern United States more temperate than the Pythons can seek locations such as region currently inhabited by pythons. underground burrows, deep water in Moreover, our results are specific to photo: Jemeema Carrigan,photo: University of Florida A female Burmese is held down canals, or similar micro-habitats to translocated pythons from southern over her open nest, showing eggs, in south escape the cold temperatures. In a Florida. Burmese pythons originating Florida. A prolific species, these snakes study conducted in the Everglades, from more temperate localities within have a clutch size of up to 80 eggs. nine of ten radio-tracked snakes their native range may be more in shallow marsh habitat perished tolerant of cold temperatures and The winter of January 2010 was one of either from the cold temperatures or would presumably be more likely to the coldest on record in south Florida. from complications experienced as a successfully become established in While these conditions consequence of the cold temperatures. temperate areas of North America. The appear to have caused an immediate, However, researchers observed susceptibility to cold we observed may yet unquantifiable, decline in the many live pythons during the walking reflect a tropical origin of the Florida population of Burmese pythons, this surveys to locate the radio-tracked pythons or acclimatization of snakes to species also showed signs of resilience snakes. These snakes were apparently warm southern Florida winters early and adaptability that could lead to able to maintain body temperatures in life.” breeding populations beyond the using micro-habitat features of the boundaries and warm climate of south landscape (Mazzotti et al. 2010). Given the climate flexibility exhibited Florida. by the Burmese python in its native Burmese pythons in the heart of the range (as analyzed through the U.S. Despite the record cold, Burmese, Everglades did survive, as evidenced Geological Survey’s climate-matching Northern African and reticulated by a mating aggregation of four adults predictions in the United States), new pythons survived in Florida, as did boa found in March 2010 and several large generations within the leading edge of constrictors. We should expect invasive adults found in April 2010. A live, the population’s nonnative range could constrictor populations to pregnant female Northern African become increasingly adaptable and able persist, rebound and possibly increase python was captured in the Bird Drive to expand to colder climates. their genetic fitness and temperature Basin Recharge area west of Miami tolerance as a result of natural selection in January 2010, immediately after January 2012 pressures caused by the unusually cold the freeze. Later (December 2010 to weather conditions in south Florida in January 2011), multi-agency efforts January 2010. resulted in the capture of several Northern African pythons. Several species continue to breed in south Florida.