National Wildlife Refuge System
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At Loxahatchee National Wildlife Refuge, turkey vultures (red heads) and black vultures (grey heads) feast on non-native fish killed by January's severe cold snap. Invasive species were among those culled by the freezing temperatures.
Credit: Sam Ward, USFWS

Cold Snap Culls Invasives − Temporarily

The record January cold snap in Florida that stunned or killed scores of sea turtles and manatees also did some little–heralded good: It took a toll on non–native invaders, including Central and South American iguanas, Cuban tree frogs, Burmese pythons and other exotic species throughout the Everglades, including its northernmost point at Arthur R. Marshall Loxahatchee National Wildlife Refuge on Florida's east coast.

Lisa Jameson, invasive species biologist at the refuge, said, "The cold–induced kill of exotic fish in the canal had vultures eating well for days." Agreed Bill Thomas, leader of the U.S. Fish and Wildlife Service's Region 4 strike team on invasive species, based at J.N. "Ding" Darling National Wildlife Refuge on Florida's southwest coast, "We'll take any help from nature we can. It beats paying for herbicides, trappers and contractors to get rid of this stuff." Iguanas fell from trees. Exotic fish floated to the surface of lakes and canals. And pythons died of exposure.

Any setback to invasives, however temporary, is welcome. Invasive species, particularly reptiles and amphibians, plague Florida, competing with natives and threatening rare animals, such as endangered wood storks at Pelican Island National Wildlife Refuge and endangered Key deer at National Key Deer Refuge. Because they rely on ambient temperatures for thermo–regulation, non–native reptiles and amphibians are especially vulnerable to prolonged chills.

On the other hand, some non–natives thrive on adversity. Take the Old World climbing fern Lygodium, scourge of Loxahatchee Refuge. When the plant gets frostbite, it reacts by spewing more spores, said Thomas. In any case, the unusual January weather may buy biologists time and give native species some respite.

For more information:
Contact Lisa Jameson at or 561-732-3684, or visit the refuge Web site at

Contact Bill Thomas at or 239-472-1100, or visit the refuge Web site at


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