Florida's Immigration Problem: tropical snakes pose an ecological threat

A young alligator lies quietly at the water's edge, momentarily oblivious to its surroundings as it basks in the warmth of the sun beating down. Moving slowly along the river's muddy sand, a boa constrictor silently approaches and then in an instant wraps itself around the gator, one coil after another. Thus begins one of nature's ageless struggles between predators deep in the tropical forest.

Except that it is not a tropical forest, but Southern Florida. And the snake is actually an invader that is disrupting the fragile ecological balance of Florida's Everglades, marshlands, and rivers.

Throughout the world, more and more we are having to contend with invasive species ranging from mussels and seaweed to lionfish, squid, and now, a laundry list of imported snakes. In the fall of 2009 the U.S. Geological Survey (USGS) issued a report listing a total of nine constrictors - including various pythons, boa constrictors, and anacondas - that were considered an ecological threat (5 were listed as a serious risk, 4 listed as medium risks).

An invading species is not out to deliberately hatch some devious plot to takeover new territory. They are typically introduced through the actions of man. Some species are transported in the bilges of large ships, like certain forms of algae and seaweed. Others are allowed to expand their range because overfishing of their natural predators have allowed them to do so, as with the Humboldt squid. And in some cases, the invasion was a deliberate attempt by man to control one problem, thereby starting another.

With Florida's snake invasion, it has come about from the importation, often illegally, of these snakes as pets. Either a snake escapes from its owner or is foolishly released into the wild because it has become unmanageable. While many snakes serve an important predatory role in controlling rodent populations, these tropical snakes have a much broader diet. Finding a comfortable home in Florida's wilderness, their numbers have been steadily growing - these snakes are also quite prolific; significant breeding populations of Burmese pythons and boa constrictors have been recorded in the state.

The U.S. Fish and Wildlife Service (USFWS) is now considering how best to approach the problem. There are several strategies on the table, a combination of which is probably called for:

• Tightening and enforcing importation restrictions of snakes from Southeast Asia, Africa, and South America.
• Increasing penalties for the accidental or deliberate release of snakes currently in captivity or making certain species illegal to own at all.
• Capturing snakes in the wild and, sadly, disposing of them and any eggs found.

Unfortunately, having imposed ourselves on nature as enablers for the planet's invasive species, we are left with the task of imposing ourselves again to hopefully set things right. No easy task, but government agencies have few choices, given what can befall an ecosystem thrown out of balance when unexpected neighbors move in.

“We have a cautionary tale with the American island of Guam and the brown treesnake,” said Dr. Robert Reed, USGS invasive species scientist and coauthor of the report. “Within 40 years of its arrival, this invasive snake has decimated the island’s native wildlife—10 of Guam’s 12 native forest birds, one of its two bat species, and about half of its native lizards are gone. The python introduction to Florida is so recent that the tally of ecological damage cannot yet be made.”

Read a report summary prepared by the USGS.
Use Defenders of Wildlife's email form to voice your concern to the USFWS (5/11 deadline).