S373 is a bill that, if passed, would ban interstate transport of 9 species of large constrictors. Ostensibly, the purpose of this bill is to protect the Everglades in southern Florida, a wonderful, unique ecosystem. I was lucky enough to visit the Everglades for the first time last spring (pics here). It is home to many amazing, native animals and plants. Unfortunately, the balance of this ecosystem is threatened by many species of non-native plants and animals. Burmese pythons, Python molurus bivittatus, have somehow become the focus of the media & politicians. Many plant species, such as Melaleuca, have done considerable damage already, but news stories featuring giant snakes get higher ratings, so that’s all the nation hears about. Humans have done incredible, irreparable harm to the Everglades, much of it has been filled and paved and is now occupied by people. The Everglades will never be what it once was, but we can protect what is left. Senator Nelson’s desire to do something in that regard is laudable, but this bill will do nothing to help the Everglades. S373 does not address any of the 900+ species of plants, 1000+ species of insects, 35+ freshwater fishes, about 20 species each of birds and mammals and only 1 of the 35 non-native reptiles & amphibians. It does cover 8 species that are not found in the Everglades, though.

This bill is based on a poorly executed study done by Rodda et al. (2009). The authors noted that the breeding population of Burmese pythons in the Everglades might be able to expand their range if the climate changes due to global warming. They created a model using only mean temperature and precipitation to predict what portions of the U.S. might provide suitable habitat. This model also lacks true presence records – they got their climate data from weather stations in the general vicinity of the natural range of the snakes. They concluded that in 100 years, given the currently predicted global warming scenario, Burmese pythons could expand their range over much of the continental U.S.

Ecological niche modeling can be a valuable tool used to identify areas that might be suitable for invasive species to become established. However, the model presented by Rodda et al. (2009) is severely flawed. Pyron et al. (2008) published a paper that illustrates the problems with the USGS report. Essentially, Rodda et al.’s (2009) model is too simplistic (only mean temperature and precipitation were used) and it generated results that are extremely unlikely. Pyron et al. (2008) generated their own model that incorporates multiple (19) climatic variables. Pyron et al.’s (2008) model for the current distribution of the Burmese python closely matches what we actually find in the native habitat and in the US. Importantly, Rodda et al’s 2009 model does NOT. This should have been a red flag to the authors that they had done something wrong. Pyron et al.’s (2008) model showing potential habitat in 100 years (using the same global warming scenario used by Rodda et al., 2009)suggests that the area that would provide suitable habitat actually SHRINKS rather than growing to expand over much of the U.S.

The niche of a species incorporates all of the various abiotic (physical) and biotic (biological) factors that are important to the survival and reproduction of a species. The total area where an organism can live is called the fundamental niche. Often, due to biotic factors such as competition or predation, an organism only occupies part of its fundamental niche. This is called the realized niche. The Everglades contains a subtropical marshland ecosystem that may be similar to what the pythons find in their native environment, but this habitat is not found anywhere else in the U.S. Predictions of what climate will be like in 100 years call for an increase in mean temperature and precipitation over much of the U.S. But, Pyron et al. (2008) point out that mean temperature and precipitation are not the only important factors. If they were, the continental U.S would already be occupied by Boa constrictor. Boa constrictor occurs only 145 km (90 miles) south of the Texas border. If mean temperature and precipitation were all that mattered, Boa constrictor would have naturally expanded its range into the U.S. over the last few thousand years. However, they are not here because there are other aspects to their niche that are missing. This begs the question of why Boa constrictor was added to the bill in the first place.

This bill would hurt the reptile industry. Tens of thousands of people would be economically impacted by this bill. For this reason, the Department of Commerce has opposed S373. I would hate to see so many friends & acquaintances hurt by this bill. I would hate to not be able to ship baby Pearl Island boas out of state (assuming I am someday successful in breeding them). I would especially hate the door that this bill would open for further banning. But, to me, the biggest factor making this bill a candidate for the shredder is that it does not provide any solution for the problem of invasive species in the Everglades. It doesn’t even offer a solution to the problem of the Burmese python in the Everglades. Instead of wasting time and money on such a flawed series of bills (S373, HR2811, HR669), it should instead be spent on research so that we can understand the various invasive species and work to eradicate them.

Please oppose S373!
http://www.kill-s373.com/
http://www.natpet.org/index.php/legislation/federal-legislation/154-python-ban-fact-sheet
http://saveoursnakes.org/
http://www.pijac.org/governmentaffairs/s373forum.asp

Pyron RA, Burbrink FT, Guiher TJ (2008) Claims of Potential Expansion throughout the U.S. by Invasive Python Species Are Contradicted by Ecological Niche Models. PLoS ONE 3(8): e2931. doi:10.1371/journal.pone.0002931

Rodda GH, Jarnevich CS, Reed RN (2009) What parts of the US mainland are climatically suitable for invasive alien pythons spreading from Everglades National Park? Biol Inv. 11(2): 241-252.

Simberloff D, Schmitz DC, Brown TC (editors) (1997) Strangers in Paradise: Impact and Management of Nonindigenous Species in Florida. Island Press. Washington DC.

For those of you wondering how Pyron et al.’s 2008 paper is a response to Rodda et al.’s 2009 paper: Rodda’s paper apparently existed as a USGS report for quite some time before finally being published. In Pyron’s list of references it is listed as “in press” meaning that it had been submitted to the journal, but had not yet been published.