How have invasive pythons impacted Florida ecosystems?
Non-native Burmese pythons have established a breeding population in South Florida and are one of the most concerning invasive species in Everglades National Park. Pythons compete with native wildlife for food, which includes mammals, birds, and other reptiles. Severe mammal declines in Everglades National Park have been linked to these Burmese pythons.
The most severe declines in native species have occurred in the remote southernmost regions of Everglades National Park, where pythons have been established the longest. In a 2012 study, populations of raccoons had dropped 99.3 percent, opossums 98.9 percent, and bobcats 87.5 percent since 1997. Marsh rabbits, cottontail rabbits, and foxes effectively disappeared.
The mammals that have declined most significantly have been regularly found in the stomachs of Burmese Pythons removed from Everglades National Park and elsewhere in Florida. Raccoons and opossums often forage for food near the water’s edge, which is a habitat frequented by pythons in search of prey.
Invaders: How Burmese Pythons Are Devouring the Everglades
Courtesy U.S. Geological Survey/photo by Lori Oberhofer, National Park Service
A Burmese python and an alligator fight in the Florida Everglades. The snakes are native to India and Southeast Asia, but they've established themselves in the wetlands of southern Florida, where they're causing havoc with local wildlife
Burmese pythons are eating machines. An adult snake can grow to nearly 20 ft., and it can eat everything from raccoons and bobcats to deer and alligators, killing its prey by constriction and then swallowing them whole. On the jungle food chain, Burmese pythons rest near the top.
Burmese pythons are also, as the name might suggest, not local to the U.S. But they are a popular pet, imported to this country from their native habitat in India and Southeast Asia. And sometimes those pets escape from their owners or are simply let go, especially in Florida, a nexus of the imported wildlife trade and one of the few parts of the U.S. with a climate and landscape to which the pythons can easily adapt. That’s how hundreds or even thousands of Burmese pythons have managed to establish themselves in the Florida Everglades, the vast protected wetlands in the southern Florida, where they’ve become a persistent challenge for local officials tasked with protecting endangered wildlife.
A study published recently in Proceedings of the National Academy of Sciences (PNAS) suggests just how big a threat the invasive Burmese pythons have become. Researchers led by Michael Dorcas of Davidson College in North Carolina looked at the distribution of mammals in the Everglades nearly 20 years ago, before Burmese pythons established themselves in the area, and then more recently. They found a drastic reduction in the number of small mammals that are typically part of a python’s diet, and they also discovered that the remaining mammals tend to be most abundant in areas that are either clear of pythons or where the snakes have only recently been spotted. The evidence is strong enough to suggest that invasive Burmese pythons are causing significant wildlife loss in the Everglades, and that the problem could worsen as the snakes continues to grow.
Dorcas told the BBC that the Burmese pythons are rearranging the food chain in the Everglades. They are a new top predator in Everglades National Park, one that shouldn’t be there. We have documented pythons eating alligators, we have also documented alligators eating pythons. It depends on who is biggest during the encounter. While the snakes have been spotted in the Everglades for at least the past 20 years, they were only recognized as fully established in 2000. Wildlife officials have tried to remove the snakes , 400 were taken out in 2009, but the damage may already be done. The PNAS researchers looked at data from detailed nighttime road surveys of the Everglades between 2003 and ’11, and compared that data with similar roadkill surveys taken between 1993 and ’99 and road surveys done in ’96 and ’97. They found:
A 98.9% decrease in the frequency of opossum observations.
A 87.5% decrease in the frequency of bobcat observations.
A total failure to detect any rabbits.
Since all of those animals can serve as a python’s dinner, and given the fact that the mammals were more common in areas where the pythons hadn’t been seen, it’s reasonable to assume that the Burmese pythons are treating the Everglades as an all-you-can-eat buffet. U.S. Geological Survey director Marcia McNutt states:
Pythons are wreaking havoc on one of America’s most beautiful, treasured and naturally bountiful ecosystems. Right now, the only hope to halt further python invasion into new areas is swift, decisive and deliberate human action.
The trouble is that it’s much easier to prevent invasive species from establishing themselves in new territory than it is to root them out once they’ve gotten comfortable. The Obama Administration banned the import and interstate commerce of Burmese pythons and a few other foreign snakes, but under pressure from the pet industry, other snakes including the boa constrictor are still allowed to be imported into the U.S.
The wildlife trade is big business, and importers will resist any new rules. Reptiles alone are worth more than $2 billion, and according to American Pet Products Manufacturers Association, some 11 million reptiles were kept as pets as recently as 2005. Perhaps, though the study is backed up by years of data and is published in one of the most reputable peer-reviewed journals in the world. In any case, invasive species pose a major threat to the U.S., costing the country some $120 billion a year. And those pythons may not be standing still, the U.S. Fish and Wildlife Service reports that they’re adapting to colder climates and may be expanding their range. Watch out, after all, humans are small mammals too.