Chasing Burmese Pythons in the Florida Everglades

Short Talks From The Hill, a podcast from the University of Arkansas, highlights research and scholarly work across the campus. Each segment features a university researcher discussing his or her work.

Bob Whitby: Hello and welcome to Short Talks from the Hill, a podcast from the University of Arkansas.  I’m Bob Whitby, a science writer at the university. I’m talking to biologist J.D. Willson about his research on invasive Burmese pythons in the Florida Everglades. Thanks for joining me, J.D.

J.D. Willson: Thank you.

BW: You’ve been studying snakes for years and co-wrote a book on them. In the forward of your book, you call the python’s take-over of south Florida “unprecedented” and say the invasion may “rival all others in the terms of its potential to completely alter the structure of native ecosystems and capture the public’s attention.” That sounds like a big problem. What are the impacts these snakes are having on the Everglades?

JDW: They’ve been recognized as established since about 2000 and since that time we’ve started to see pretty dramatic escalating changes in the Florida Everglade’s ecosystem relating to predation by pythons. So we had a study, several years ago now, that documented basically most mammals disappearing from where pythons have been established the longest and are most common. So, virtually complete disappearance of most middle-sized mammals. Things like rabbits, raccoons, opossums, even declines in things like deer and bobcats and some of the more carnivorous species. In some areas of the southern Everglades it’s very uncommon to rare to even see one of these mammals anymore. It’s actually kind of spooky to do field work down there and not see the mammals that we’re so used to seeing frequently. And of course there are some of the species that pythons feed on frequently. There have been several subsequent studies that have really confirmed the link between pythons and declines in those mammals. In fact they tried to reintroduce rabbits to areas where they have been wiped out and nearly all of those rabbits got eaten by pythons and the populations failed to re-establish. So they seem to be really changing the food web of the system and the most recent study we’ve done really focused on the larger scale implication of how that might change the Florida ecosystem.

BW: So you’ve said they’ve been in the Florida Everglades since about the early 2000s. Where did they come from?

JDW: They’ve been recognized as breeding and established as an invasive species since about 2000. Our research suggests that they were probably there a lot longer. There is a lot of controversy about how they got introduced in the first place. But one thing that is very hard to argue is they came from anywhere other than the pet trade. That’s really the only reason these snakes exist in our country.  They’re native to much of southern and south eastern Asia. They’ve got a very broad range that spans all different habitats from tropical rainforest to desert, even up into the foothills of the Himalayas in India.  Really since the 1970s or 80s they’ve been very common pet snakes. So through some combination of accidental or intentional release or escape, these snakes got into the Everglades and apparently found it very much to their liking.

BW: Describe the Burmese pythons. What do they look like?

JDW: The Burmese python is pretty widely recognized as the third largest snake in the world depending on how you measure size. If it’s length or weight, but they can reach certainly lengths between 15 and 20 feet regularly, even in the wild. I think the record in Florida is now between 17 and 19 feet. Depending on which one you recognize as a legitimate record or not. But there have been several individuals in the 17-18 foot range. These weigh upwards of one hundred pounds or more. They’re a magnificent animal. Beautifully patterned, of course in the case of a pet snake, this is a beautiful animal to display. It’s fun to look at in a zoo. In their natural environment this provides camouflage so they’re amazingly camouflaged. They can blend in to a little bit of leaf litter, or they spend a lot of time in the water, a little bit of aquatic vegetation and they virtually disappear. In fact that’s one of the problems with studying them is that they’re so hard to find, even where we know they’re common.

BW: Do you have any idea how many there are in the Everglades and are they spreading north still? Is there some place that they’re going to be stopped by the weather?

JDW: The answer to both those questions is no, we really don’t know yet. Those are topics of active research right now. In terms of how many there are, the problem there is we know they’re common in many areas. We know there are parts of south Florida where dozens to hundreds have been removed from even relatively small, like a canal bank along one of the canals over the course of a year or two.  We still find them there, we certainly haven’t eliminated them from anywhere as far as we can tell. But just how many there are is really hard to tell. In fact, we did a detection study where had snakes in a large sort of enclosure and we had people come in and experimentally search for them. In that study, only two snakes were found out of 200 hundred possibilities of detection. So this suggests that essentially, even in a cage, you walk by 99 for every 1 that you see. They’re even harder to find in natural habitat, especially when you get into some of the tangled mangrove or sawgrass type habitats of southern Florida. So, we’re working in news way to develop population models to estimate how many So, we’re working on news way to develop population models to estimate how many there are.  We know there’s many. I mean thousands have been removed. They’re spread over an area of several thousand square miles now, so the area that we are talking about is just gigantic. But in terms of an actual density estimate, that’s sort of the golden question. In terms of how far they can spread, that’s the most controversial question. That’s also still an area of active research. There have been several studies that have tried to use a technique called Climate Matching to predict, basically where suitable climate exists for them. So basically the idea there is you take known localities where they occur in Asia, look at the climate there and match to similar climate here in North America. Depending on which climate variables you include in those, the estimates range anywhere from basically the Florida peninsula, maybe parts of the Gulf Coast, all the way…there’s one of the better supported models actually, that suggest that they could go all the way up into the southern tier of the U.S., all the way up to even southern Arkansas, Washington, D.C., or the West Coast.

BW: Do the pose any danger to humans?

JDW: That’s also a question that is frequently asked. I’ve typically answered that the danger to humans that often portrayed by the media is exaggerated. These are not necessarily “man-eaters” who are out looking for humans. But they are large, powerful, carnivorous animals and with the numbers that are out there, it’s certainly a possibility that someone could have a predatory-type interaction with one. In their native range, they to the extent that there are attacks of “wild” pythons on humans, thus far the evidence would suggest that’s similar in Florida, maybe something sort of like an alligator, where thousands and thousands to millions of alligators coexist with people all the time. Most of those don’t have any negative interactions with people. Every once in a while, there is a situation where a bad situation arises where one gets to acclimated to being fed by people and you end up with a problem on your hands.

BW: You recently published a study in the Journal of Applied Ecology about the effects of the pythons.  Can you talk a little bit about that?

JDW: Yes, so this is an extension of our previous research on the impacts of pythons on mammals and here we basically looked at the broader scale of indirect effects that pythons might be having on the Florida ecosystem. In that study, we actually took it a step further and said, “If mammals are disappearing, because of pythons, what effect are mammal declines having on other species in the system that might not be directly preyed upon by the pythons? The species we decided to focus on for that were turtles because turtles are not preyed upon by pythons, but turtle nests are frequently predated by raccoons, opossums, and other small to mid-size mammals that have declined where pythons are common. So in this study we basically went out and created artificial turtle nests across the range of pythons, including areas where they are common and are few mammals, all the way out to areas where there are more pythons and mammals are very common. We basically found that in areas where mammals have declined, turtle nesting success apparently is a lot higher than it is naturally in areas where pythons are not there yet. So this is actually a positive effect of pythons for turtles, but that’s optimistic. The flip side of that is it suggests that these effects of pythons is trickling through the ecosystem and cascading through different components of that food web. You might imagine that loss of mammals might effecting all types of ecosystem processes like vegetation dynamics, nutrient sampling, other aspects of the food web, and we really maybe seeing a change in the whole overall ecosystem. The really scary thing is it shows a direct parallel to the case of the brown tree snake which is the other sort of poster child of invasive snakes. They invaded the island of Guam in the South Pacific in the 1950s, wiped out most of the native birds, which of course was a conservation tragedy. But recent research has even suggested that that’s even trickled down through that ecosystem and changed the forest structure. The types of trees that are growing because birds are spreading seeds or pollinating plants. So it’s changed the invertebrate communities with spiders as predators rather than birds, which would normally not be the major insect predator. We seem to be seeing a sort of a parallel situation arise here in the Everglades.

BW: Is there anything that can be done to stop; to get rid of the snakes?

JDW: There’s definitely no golden arrow at this point, or any easy solution. That doesn’t mean we can’t do anything about it. Currently there’s a lot of active research going into how to best capture these snakes. Once we combine an estimate of how many there are with how we can best capture them, we can figure out how to control them or reduce their populations at least maybe in small areas. Such as areas where they might come into contact with sensitive species. The Florida Keys are a prime example. They’re starting to get onto the Florida Keys and there’s a whole variety of species on the Florida Keys that we would like to protect. So large scale eradication—not at this point. But small scale solutions—I think we’re heading in that direction. And with continued research, I think there’s hope that we could continue to improve our methods such that we could make a bigger effect on their populations.

BW: Music for Short Talks from the Hill was written and performed by Ben Harris, guitar instructor at the University of Arkansas.  For more information and additional podcasts, go to KUAF.com or ResearchFrontiers.uark.edu, the home of research news at the University of Arkansas.