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Exotic South Florida Part II: The Genesis of the Burmese Python

09 May

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.

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4 responses to “Exotic South Florida Part II: The Genesis of the Burmese Python

  1. Vic Herrick

    19/01/2012 at 5:38 am

    I think this is fascinating and it is great to hear it from a person with first person experience. Regarding the “genesis” of this population: Has anyone done DNA typing, tried to identify how much diversiity exists in them? Are they all closely related? Are you able to determine where they descneded from in Asia? Maybe if from Thailand they won’t be real cold tolerant, but if from further north or high altitude, they may be tougher and more resilient than we think… I really would be thrilled to see them in the “wild” of Florida if not SE Asia, I wll have to give it a try. Do most folks euthanize them when they are found? What is the National Park policy on that….hands off or destroy them?

    Vic Herrick
    Imperial Valley, CA.

     
  2. Josh

    20/01/2012 at 5:22 pm

    Vic,

    There was a genetics study done by Collins, et al, and I believe most of them were vietnamese in descent.

    As far as Everglades National Park, like all national parks, it has a strictly hands off rule with wildlife, even, unfortunately, Burmese Pythons. It would be nice to see that change to allow a more widespread control effort, but that’s the way it stands now. In fact, many of the areas the Pythons occur are run by government organizations which bog down any permitees with paperwork, fees and whatnot that most definitely reduces the efficiency of any python removal program. FWC, for instance, has a policy of mandating any permitted python hunters to visit several WMAs, even a couple where python sightings are rare – this is the reason I haven’t ever pursued a personal python permit from FWC: I don’t want to waste my time and gas money searching poor habitat.

    That said, I have heard that some non-permitted individuals in ENP will run over pythons if they see them. I have no idea if that’s legal or not, and I’ve always been permitted by the park so never had to make that decision. The best (and only surefire legal) thing to do is to not touch them and call the Python Hotline (888)ivegot1.

    Thanks,

    -Josh

     
  3. Richard Stanley

    10/03/2012 at 7:25 pm

    Based on the distribution map you can view with the link I have set forth below, the greatest concentration of Burmese pythons has been found near Homestead/Florida City; and radiates north, west and south from there. This would support the Hurricane Andrew theory. Check it out. http://www.eddmaps.org/florida/distribution/viewmap.cfm?sub=20461

     
  4. Josh

    11/03/2012 at 2:16 am

    Hi Richard,

    Thanks for the comments. You’re right in that EDDMaps shows the highest concentration of captures at and around the entrance to ENP; but that does not necessarily equate to the python population – there’s a couple of reasons for my thinking.

    Firstly, EDDMaps has only been mapping python sightings for a short time, I’d have to check but I believe only since 2004-2005-ish. So, although they did use some historic records, most of the records are since its inception and since the pythons had “spread out” from where ever their source was. Additionally, there’s no standardized route or anything for EDDMaps, so there’s no data on search effort, etc: There could be 5x the traffic looking for pythons there over Flamingo.

    Secondly, numbers of pythons do not necessarily equate to their point of genesis. Just because the python population stated in ‘Area X,’ doesn’t mean that they’ll be most dense in ‘Area X.’ Habitat suitability, competition and resource availability are the biggest factors determining a species abundance and distribution.

    That said; I’m not saying that the “Adam and Eve” pythons that started the Florida population conclusively came Flamingo or Homestead – but in my opinion the preponderance of evidence points towards Flamingo.

    Thanks,

    -Josh

     

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