Until the past 5 years or so, the Burmese Python (Python molurus bivittatus) wasn’t a part of the usual megafauna thought of in reference to South Florida. That’s all changed over the past couple of years thanks to a plethora of news stories, National Geographic specials, proposed bans and supposed experts.
I have a deep interest in these animals and have undertaken countless field hours to learn more about their ecology; and have published my findings both in an academic journal (“An effect of Burmese pythons. (Python molurus bivittatus) on mammal populations in southern Florida” Published in Florida Scientist, 2011), as well as an extensive section in my upcoming field guide.
The most common question I get from people in reference to the pythons is something along the lines of: “So, these are people’s pets crawling around that they let go?” I’m afraid not. Though the Pythons very likely came from the pet trade, the current profusion in Florida’s Everglades are individuals hatched and raised among the sawgrass, cypress and hardwood hammocks: not ever pets themselves. That said, there’s three main theories on where these animals came from, and I’ll mention them all currently:
The Pet Theory – The one regular touted by those with superficial python interest: newscasters, politicians and the general public (No offense to the general public, just most people’s lives aren’t affected by pythons too much.) The theory goes that a bunch of people over the years have bought cute little 1.5 – 2 foot long Burmese Pythons which fed happily on mice, only to find themselves with a 8 foot snake a year later. Being outside of the tolerance for most pet owners, and curiously eying ‘Mittens,’ the family cat; these animals were dumped in the the Everglades and eventually found other pythonic cast-offs and got together and had lots of babies and lived happily ever after.
There’s a couple problems here though: There’s an ecological concept called the “Minimum Viable Population” (MVP) which states that there must be a certain number of individuals to find each other and have a sustainable population. It’s unlikely that there were enough pythons released in one area to reach the MVP: according to Traill et al. (See citation below) the median (average) MVP for published species is 4169 individuals. That’s a lot of irresponsible pet owners. That said, given there large clutch size and a number of other factors, the MVP is likely a lot lower for Burmese Pythons; but suffice to say it’s probably more than a couple individuals.
One other issue is that the pythons started originally showing up at Flamingo – an area of Everglades National Park (ENP) at the extreme southern tip of the peninsula and a 40 mile drive from the entrance. So, in order to buy this theory, one would either have to contest that the python population started at Flamingo, or they would have to believe that an irresponsible pet owner, not willing to care for their snake any longer drove two hours to the extreme south of ENP instead of dumping it at the first patch of sawgrass they saw. A little bit of a stretch, in my humble opinion.
The “Hurricane Andrew” Theory – Getting a little more plausible here. This theory gets over the problem of the MVP by stating that reptile importers in Miami and Homestead lost hundreds (if not thousands) of Burmese Pythons when Hurricane Andrew hit in 1992. In fact, we do know for certain that Burmese pythons were lost in this storm: I seem to recall that even Miami Metrozoo lost a couple. But there still remains the belief that the population started in Flamingo. If the python population did start at Flamingo, I find it more than a little unlikely that the hundreds of escaped Burms migrated 50 or 60 miles from Homestead and Florida City before starting a breeding colony. Now, it is entirely possible that the original population was not from Flamingo, but the first sightings were all in that area so the evidence strongly suggests it. Additionally, Hurricane Andrew occurred in August, which means any escaped pythons would have around 6 months to disperse before the breeding season begins, around February, making finding each other to breed more difficult.
The “Ranch” or “Cash Crop” Theory – It’s only in the last few years (and owing a lot to the pythons) that exotic and invasive species are something which is on the radar of the general public, or even those who breed reptiles. Many times in the past, animals have been released by importers, breeders, or pet shops in order to establish a “ranch” the animals: it means free food and often times the animals will breed prolifically in the wild; allowing the offspring to be collected at a later date. This has been done with a number of species in Florida’s past (see Gillette, et al.), and I believe is likely the case with the pythons. It explains why a.) the pythons might have had their genesis at Flamingo, as well as b.) how enough pythons “met up” to sustain a MVP: a purposeful release could have included large, gravid females and other adults which would have been able to reproduce quickly.
Here’s another shot of that 4.43 meter female I found 2 years ago. Myself and my friend Donald. One of many we’ve found in the ‘Glades:
–Gillette, C.R., K.L. Krysko, J.A. Wasilewski, G.N. Kieckhefer III, E.F. Metzger III, M.R. Rochford, and D. Cueva. 2010. Oustalet’s Chameleon, Furcifer oustaleti (Mocquard 1894) (Chamaeleonidae), a Non-indigenous Species Newly Established in Florida. IRCF Reptiles & Amphibians 17:248-249.
-Traill LW, Bradshaw JA, Brook BW (2007). “Minimum viable population size: A meta-analysis of 30 years of published estimates”. Biological Conservation 139 (1-2): 159–166.