Throughout the 1980s raccoons in the Everglades National Park were such a nuisance, a special program had to be initiated to keep them under control. Yet today the number of raccoons has decreased by over 90 percent. What is causing the raccoon and other mammals in the park to decline? An invasive python imported by the pet trade.
The Burmese Python (Python molurus bivittatus), a large constrictor from South East Asia, can grow up to 19 feet in length making them one of the largest snakes in the world. Pythons are a popular pet but since they are so large they can be difficult to take care of or simply grow too big to be kept as pets by inexperienced owners. Such people often will release their snake into the wild instead of putting in the effort to find it a new home. In most areas in the US, these released snakes or escapees would simply die. However, the Florida everglades are a perfect home for them. The pythons released in Florida mingled with some that escaped during the destruction of Hurricane Andrew have thrived and formed their own population. The snakes are now breeding in the wild and have established a range spanning thousands of kilometers including the Everglades National Park (1.5 million acres).
Severe mammal decline coincides with proliferation of invasive Burmese pythons in Everglades National Park, a recent study lead by Michael Dorcas, is the first study to show these snakes are having an ecological effect on their new home. To try to determine the impact the pythons are having on native species, researchers compared road survey data from before and after the introduction of the python. Road surveys are a simple procedure where researchers drive down certain roads and record the number of observed live and road kill species. The surveys in this study were conducted at night on Main Park Road and Research Road in the Everglades National Park.
Their data showed that prior to the introduction of the pythons, native mammals like raccoons, opossums, and rabbits were the most common animals found in Everglades National Park. Data from 2003-2011, after the introduction of the python, showed a 99.3% decrease in raccoons, 98.9% decrease in in opossums, 94.1% decrease in white tailed deer, and 87.5% decrease in bobcats. Additionally, no rabbits or foxes could be found in the pythons’ range.
Scientists believe that the pythons are responsible for the reduced mammal populations for several reasons. The timing of the pythons’ introduction to the area coincides with the beginning of the mammal disappearances. Data also showed that in areas where the pythons were only introduced recently, the populations of native vertebrates had not declined as much as in areas where they have been long established. Most of the species that have been declining are known to be prey of the pythons. Since the number of snakes has been increasing, it makes sense that the missing mammals are feeding the growing population. Some people have suggested that the decline in these species could be attributed to a disease. However experts disagree, arguing that the likelihood of a disease affecting such a broad range of mammals in separate families is extremely low. Scientists have also ruled out human interference as the cause since the Everglades National Park is protected from hunting and trapping.
Because of the effects of this and other studies, the Burmese Python has been labeled as an invasive species in the United States. The term invasive species refers to a non-native group of animals that adversely affects the habitat they invade. Other invasive snakes have been implicated in native vertebrate decline in the past. In the case of the Brown Tree Snake, it took more than 30 years for their impact in Guam to be recognized. Cases like these need to be learned from so that similar mistakes are not made. Large scale efforts need to be made to remove the python now before irrevocable damage occurs.
Since so many common species are declining, researchers are concerned that rare species may be on the menu as well. In addition to eating medium sized mammals, the pythons are consuming endangered species like the Wood Stork and the Key Largo Woodrat along with (can you believe it?) American Alligators and White tailed deer. Conservationists fear that since the pythons are already consuming such large prey, they may expand their diet to include the highly endangered Florida panther. This species is already so threatened that adding a powerful predator like the python may wipe it out completely. Since the pythons have been known to consume leopards in Asia, steps need to be taken to ensure the panthers’ safety.
However, some ecologists remain skeptical about the threat. Whit Gibbons, head of outreach for the Savannah River Ecology Lab at the University of Georgia, believes the native species that have been declining will adapt the longer the python remains in Florida and their numbers will again increase. Regardless, scientists agree that although it is unlikely that common species will become extinct in Florida, conservation efforts need to be made to remain proactive in this fight. They can’t wait until the python wipes out an endangered species to their threat seriously. Action needs to be taken now.
Luckily, some conservation efforts are already underway. Workers in the Everglades National Park have been removing snakes as quickly as they can find them but the numbers have grown so large that it’s difficult to keep up. In 2010 over 300 snakes were caught and removed from the park. This number has been drastically increasing from 2000 when the snakes were first established there. To attempt to prevent more snakes from being introduced to the area, on January 17th the US Department of the Interior banned importation of a number of snakes including the Burmese python. The Nature Conservancy’s “Python Patrol” is also hard at work taking steps to ensure that the pythons don’t spread to the Florida Keys.
The invasion of the Burmese python is just one more example of the ecological implications of importing foreign species. The potential effects of such invasive like the Burmese python, Gypsy moth, Kudzu, Zebra muscle, and Multiflora rose were not considered before their introduction to the United States. Now they are producing devastating ecological effects. To prevent future invasives, stricter regulation of importation of non-native species needs to be implemented. In addition, people who choose to own exotic pets like the Burmese need to be educated about their pets beforehand and tighter restriction should be placed on owners of such pets to ensure that they understand the responsibilities involved. I believe that if proper education of such people had occurred when they were first considering owning such a large snake, many would have chosen to purchase a better “starter” snake that they could have provided appropriate care for. In addition, even experienced owners should make sure that their snakes are in good quality cages to prevent escapees from adding to the problem. I just hope that the python can be stopped before it is responsible for the extinction of one of Florida’s endangered species.
Disclaimer: Photos do not belong to me. They link to their source.