During the last 30 years about 1 million giant constrictor snakes, including pythons and anacondas, have been imported to the United States, and there’s now a thriving domestic breeding industry.
A brooding Burmese Python lifted from her eggs in Florida.
To each his or her own, I suppose, but scientists are growing increasingly worried about the prospect of these non-native predators establishing themselves widely in the United States, which could have devastating economic and environmental effects.
Already, scientists say Burmese pythons and boa constrictors have established breeding populations in South Florida’s wild areas, and there’s strong evidence of the northern African python doing so as well.
The U.S. Geological Survey has just completed a major report (see abstract, see .pdf of report) on the probability of these species spreading in the wild (for some varieties of constrictor, it is high) and the threat they pose to the economy and environment.
I’ve spent part of this afternoon browsing through the 300-page report and I found it fairly chilling. Especially this paragraph buried deep within:
A most difficult aspect of this threat is its irreversibility. Once an introduced giant constrictor becomes well-established, there is no known method for removing the threat, and thus recovery of endangered species in an infested area is a prospect likely to be diminished or even eliminated permanently. In this respect, invasive species constitute a more enduring threat than pollution, overexploitation, or habitat degradation.
Of the nine species profiled in the report, it appears that much of Texas, including the Houston area, has a climate suitable to two. They are the Burmese python and the Boa constrictor. The maps below show the area of the country that the scientists believe is ultimately suitable for each species.
First, the Burmese python, which on average grow to 18 feet and about 160 pounds:
And here’s the habitat for the Boa constrictor, which average about 8 feet and 60 pounds:
So what are some of the risks if these large constrictors become established (the probability is deemed “high” for five of the nine species, including the Burmese python and Boa) in the United States? Some highlights from the report:
• A potentially devastating impact to the nation’s agriculture could occur if the cattle disease heartwater or some other tick-borne disease were to become established in the United States and be transmissible through reptile ticks. African tick species that use pythons as hosts may be vectors of heartwater, and these ticks have been observed to transfer to other hosts, including other giant constrictors, other reptiles, and dogs. Because multiple python species are held captive together in the commercial trade, such transmission has ample opportunities to occur prior to retail sales.
• Direct predation on livestock will occur if any of the giant constrictors become established in the United States. This prediction is very certain, in part because livestock losses have been widely documented in Florida (by Burmese Pythons, Northern African Pythons, and Reticulated Pythons). However, the extent of the damage is much less certain. Free-ranging, small-to-medium livestock, especially poultry, would be expected to be most heavily impacted. Pigs may be favored prey for some species, especially the Asian pythons.
• Predation on pets is likely to be of limited economic importance, but acutely felt by the bereaved pet owner. If experience with alligators has predictive value for understanding other large reptile-human exchanges, encounters between companion animals and snakes have the potential to escalate into a human health risk (because aggrieved pet owners sometimes unwisely choose to defend their pets against the reptile).
• With the possible exception of the Reticulated Python, most giant constrictors’ impact on human health will be in the realm of feared attacks rather than actual unprovoked events. Most of the area of the United States mainland that is likely inhabitable by Reticulated Pythons is lightly populated, except for cities and towns along the Florida and Texas coasts. Though the number of actual attacks is likely to be small, such events as do take place could significantly degrade the already angst-ridden psychological relationship between people and wetlands.
• All of the giant constrictors could further endanger watchable wildlife species that presently constitute a significant draw for eco-tourists. Colonial bird rookeries (for example, Wood Storks) are a particular tourist draw, and are potentially vulnerable to depredation by a new nocturnal and opportunistically arboreal predator. Where their ranges overlap, all of the giant constrictors could significantly reduce stocks of economically-important fur-bearers such as beaver and muskrats.
• Based on experience with the Brown Treesnake and other introduced snakes, the greatest environmental impact of invasion by giant constrictors would be predation on endangered species, either via further endangerment or outright extinction.