UF Research: Kingsnakes Disappearing From State

November 21, 2001

GAINESVILLE, Fla. — The kingsnake, so named because it eats poisonous snakes and is immune to their venom, is rapidly disappearing from Florida, according to new research by a University of Florida scientist.

Once common throughout the state, the kingsnake has vanished from many Florida counties, said Kenneth Krysko, a UF student who researched the snake’s ecological status as part of his doctoral dissertation. Causes may include habitat loss, overzealous collection by reptile fans or dealers and loss of genetic diversity, but scientists don’t know the precise cause.

“They’re not nearly as abundant as they used to be, and we don’t know why,” said F. Wayne King, a professor and herpetologist at UF’s Florida Museum of Natural History and the chairman of Krysko’s dissertation committee.

Three kingsnake subspecies have traditionally occupied Florida. These are the Florida kingsnake, which dominates the Florida peninsula, the eastern kingsnake, which lives in the western Panhandle, and a third as-yet unnamed subspecies in the Apalachicola National Forest identified by Krysko as part of his research. Even within one subspecies, kingsnakes’ appearances vary widely, but most kingsnakes have light-colored bands, blunted heads and reach a maximum length of slightly over six feet.

Kingsnakes are unusual among snakes because their diet includes other snakes, including poisonous ones such as rattlesnakes, and they are immune to snake venom. Kingsnakes are also relatively docile, a quality that makes them popular in the reptile trade and has contributed to their plight, Krysko said.

“It’s obvious that collecting has a real drastic effect at the population level, especially in southern Miami-Dade County,” he said.

For his research, Krysko culled scientific literature, museum collections and scientists’ field notes for examples of kingsnake sightings or records in Florida dating back to 1858. The resulting geographic database suggests that, while the snakes once occupied at least 54 of Florida’s 67 counties, their range has shrunk considerably in recent decades. Records indicate the existence of kingsnakes in only 23 counties between 1990 and 1999, despite an increase in the number of collectors and herpetologists in the field.

Krysko said loss of the snake’s favored habitat in woods near water bodies is one factor contributing to its decline. Much of the habitat that remains is disconnected, meaning the snakes cannot share genes with neighboring populations.

Another potential threat is the spread of non-native fire ants, which some scientists believe target kingsnake eggs and young. Still another danger is that, as predators at the top of the food chain, kingsnakes may ingest damaging or deadly levels of heavy metals and pesticides, Krysko said.

There were at least four formerly large populations of kingsnakes statewide, including at Paynes Prairie in Alachua County. King said it was easy to find kingsnakes on the prairie in the 1950s and early 60s.

“Now, they’re gone,” he said. “They don’t exist on the prairie as far as we know.”

Only one kingsnake population, south of Lake Okeechobee in the sugar cane plantations, remains healthy, Krysko said. Kingsnakes flourish in this area because the sugar cane fields and irrigation canals support large populations of snakes and other rodents, he said. Ironically, the planned Everglades restoration threatens this population because it will replace some sugar cane farms, he said.

“We’ve created this great habitat there for this species that has declined everywhere else,” he said.

Krysko and King said the study’s findings indicate that the kingsnake should be protected by the state of Florida. Florida currently has two snakes on its “threatened” list: The Atlantic salt marsh snake and eastern indigo snake.