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Dangerous Everglades Invasive
Snakes Are Here To Stay

On January 20, 2012, Florida Keys Vacation conducted an interview with Research Wildlife Biologist and noted author, Robert Reed.

Bob Reed is an expert in the Invasive Species Science Branch of the USGS Fort Collins Science Center in Fort Collins, Colorado.

The reason for the interview was to discuss the current Everglades National Park problem which has reached critical mass.

These Everglades invasive snakes threaten rare, and endangered species as well as the balance of the area's delicate ecosystem.

Our interview with Bob Reed was timely as we decided to hold it the day after the United States Secretary of the Interior, Ken Salazar, made a formal announcement regarding 4 injurious snake species in Florida. This was regarding policy changes the government was implementing as a means of controlling the pervasive threat posed by these Everglades invasive snakes.

Reticulated Python

Reticulated Python, Photo Credit Bjorn Lardner

On January, 16, 2012, the Secretary of the Interior put into effect measures to be implemented within 60 days regarding these 4 declared injurious species. The new Federal Rule dictates that their will be no breeding, nor importing or trafficking across state lines of live snakes, gametes, eggs, or hybrids.

As of 2010, the State of Florida passed a law prohibiting the sale of these snakes in the State. The 2010 law also grandfathered in any snakes currently owned, but added stipulations to their ownership. All of these snakes were required to be registered, micro chipped and properly caged to prevent possible escape.

The invasive species list identified 4 injurious Everglades snakes species. The named snakes along with their estimated maximum lengths are as follows.

The Burmese python up to 23', the North African Rock python up to 20', the South African Rock Python up to 20', and the Yellow Anaconda up to 20'. Even though these are estimated maximum lengths, the larger species have been recorded at around 30'.

There are 5 other Everglades invasive snakes species which are currently being evaluated. They too could possibly be added to a similar list soon. They include the Beni anaconda, boa constrictor, DeSchauensee's anaconda, green anaconda, and the reticulated python.

Following is the interview with Bob Reed and the helpful perspective he's put on a controversial, and often bipolar issue.

Adaptability of Everglades Invasive Snakes

FKV: The winter of 2010 was unusually cold for the Everglades and the Florida Keys. Was there any significant decimation to the python population because of this cold weather?

BR: The number of Everglades invasive snakes that died during the winter of 2010 were in the thousands, but the number of snakes that currently live in the Everglades are in the tens of thousands. The cold had very little overall impact on the size of the snake population.

FKV: What is the minimal temperature a python or constrictor can withstand to survive?

BR: That's a question that can't be answered directly with the available evidence we have. Obviously any snake that freezes solid will die, but if you say that snakes can't live anywhere where it freezes, then that means there are no snakes living in the Midwestern and Northern United States. Obviously that's not true.

What really matters is how the snakes are able to respond to cold weather. Do they go into underground refuges, and holes in stumps and trees? Snakes that aren't adapted to cold weather will respond differently to the cold, than snakes who are adapted to it. It becomes a behavioral issue as to whether these Everglades invasive snakes have the necessary skills to seek protection and hide when it's cold, or whether they do not.

Spectacular Water Views Are a Highlight at Beaches in Key West

Arican Rock Python, Photo Credit US Geological Survey

Burmese python are more adapted to the cold than the African Rock python. They live in climates where it does get cold. This means it's more likely that this species of Everglades invasive snakes could possibly travel a greater distance north. Even though these snakes can travel quite large distances in relatively short periods, if they were to travel to the northern States this would be an incremental journey over a period of many years.

FKV: You helped to author a report that caused quite a stir. The portion of the report that caused the reaction focused on the possibility that pythons could eventually be found as far north as Northern Delaware and Oregon by 2100. That would make them more than just an Everglades invasive snakes problem, it would take on larger national overtones. Is this really possible?

BR: That report was taken out of context. The report showed areas of the United States that have rainfall and temperatures that are similar to the natural occupied range of this species. It showed U.S. climate that pythons could possibly survive in, if they were established there.

It would take numerous years, under perfect circumstances, for pythons which are large part of the Everglades invasive snakes problem, to reach those distances. Their travel would be incremental and would of course depend on their ability to adapt to the cold weather, their ability to seek appropriate shelter, and to find a reliable food supply over the duration of the winter.

Of course in the winter they also wouldn't be as active, they would be more sluggish. Typically in the winter, even in the Everglades during a cold front, you'll see snakes only in the morning where they go out and sun themselves. They then return to their den to maintain their body heat.

The Burmese python is more acclimated to cold so it's chances of surviving further north is greater. On the other hand, the African Rock python comes from a warm climate and is not at all adapted to cold weather. It's chances of surviving where it's colder are much smaller, and it's unlikely that the African Rock python would extend any further north than central Florida.

So to answer your question, it is possible that these Everglades invasive snakes could survive and extend further north, but it's highly unlikely. Especially with greater public awareness of the python problem, we can take preventative measures to help hunt and kill them as they try to spread outside their current territory.

Florida Keys Vacation
Everglades Invasive Snakes Sidebar

This link to Early Detection and Distribution Mapping System is for all invasive species in the State of Florida. The information is incredibly remarkable and long. That latter fact alone is scary when you realize how many species are having a negative impact on this beautiful State.

The reason this link is included is so you can see where the different Everglades invasive snakes have been documented outside of this region. You can also see the numbers found.

By scrolling through the list you can look for references to the different species of python, anaconda and boa constrictor. There are many other interesting non-snake invasive species listed as well, and you can review that information as well.

This video discusses the roadkill survey that was conducted in an effort to help calculate the detrimental impact the pythons and other invasive species were having on wildlife in the Everglades.

Python Research and Roadkill Survey
Courtesy of National Park Service on YouTube

Propagation Of Everglades Invasive Snakes

FKV: There are 9 Everglades invasive snakes that are constrictors. Is any species more dominate or are they equal in terms of their territory?

BR: There isn't any dominance of snakes over territory. Snakes don't typically fight other snakes or eat other snakes, so co-habitation is not a problem.

The problem with these snakes is that they are very adaptable. They're generalist predators, which means they don't rely on one food source. If one source is depleted, they move on to another suitable source. They are fast growing, mature quickly and have large numbers of young. They live in a variety of environments. The young will live in trees, while mature snakes live in the water and on the ground. Since they can co-habitat side by side, can eat a variety of food sources, and live in different environments, their numbers continually escalate.

FKV: What do you estimate the Everglades invasive snakes constrictor population to be?

BR: It's difficult to determine that answer with any certitude because we cannot calculate their population density based on normal procedures. Normally you would fit captured animals with a collar so you can monitor them. Based upon how often they are caught in the specific geographic area you're then able to mathematically determine the density of that species for the area in question. However with pythons and other Everglades invasive snakes, whenever one is found - it's killed. This makes it impossible to say with any exactness what their numbers actually are. They certainly are not in the thousands as some suggest, they are in the tens of thousands.

Python on Her Nest

Python On Her Nest, Photo Credit Jemeema Carrigan, U of F

FKV: One of the conflicting arguments I keep coming across is whether these snakes are propagating. A number of sources insist that this is not happening. They state that there have been no nests found, that the smaller snakes are recently released juveniles and that the pythons have not begun to breed. The increased numbers are due to more snakes being released into the wild. Is this true? Why aren't they propagating?

BR: Unfortunately, anyone who says we don't have a breeding population in the Everglades is either unintentionally or intentionally trying to hide the fact that we do. They have been breeding in the area since the 1980's. In fact, the largest nest found in the Everglades had 78 eggs in it. There's no question these Everglades invasive snakes are breeding, and their numbers are increasing steadily.

FKV: How often do the females lay eggs then?

BR: They lay eggs every 2 - 3 years.

FKV: Since you've confirmed that these Everglades invasive snakes are breeding, another issue which I've found interesting is the fear that they would crossbreed and produce a super snake. Is this likely?

BR: I think it's likely that eventually these 2 species will hybridize, but everything we know about hybridized species is that they're not a super species. This doesn't mean we should discount this from happening because it could. If it did, it could mean that the resulting hybridized snake could have the African Rock python's preference for larger prey. This could end up being a new dominant trait in the hybridized species. If this happened, it would have even more of a significant impact on the animals that are higher up in the food chain, specifically the panther which is endangered.

Understanding The Everglades
Invasive Snakes Problem

FKV: Can you explain some of the different problems facing us with these Everglades invasive snakes?

BR: Well the area is perfect for their survival. They have no natural enemies. They have an abundance of water and food. The climate is perfect. They can hide undetected so it's virtually impossible to hunt them down and kill them. This is what people don't understand. You can't just normally round up these snakes and kill them.

FKV: I agree. It's not like in northern Texas where they have rattlesnake roundups on the open prairie. Here you have this massive slow moving body of water that's completely filled with reeds. It's impossible so see anything in that kind of dense cover. Plus the water is infested with not just these snakes, but other poisonous snakes, alligator and crocodile. You can't just go wading around trying to find one, and in a boat, they would be virtually impossible to see.

BR: That's true, and they are the master of camouflage. That's how they survive. They are a sit and wait predatory species. This means they're in a state of restful alertness, waiting for their prey to come by and so they can strike without being seen. The Everglades provides them with complete cover so they are never seen. It's impossible to track down and kill them when they can't be seen. On a daily basis, the detection probabilities of seeing one is 1:1,000. Those are very small or poor odds which is why it would impossible to eradicate them.

We were in the Everglades National Park speaking with a group of people, and in the water, only a few feet away from us, was a large python. Even though it had been right beside us, no one even noticed it until it swam away.

FKV: Something else that was interesting was to discover that these snakes have a greater tolerance for salt water than was realized. Do you think they could swim to the Bahamas or Bermuda and become established there?

BR: These Everglades invasive snakes also have a much higher tolerance for saltwater than what was originally believed. Whether they could swim to the Bahamas, I don't know. It certainly wouldn't happen immediately but over time, evolution time meaning hundreds and hundreds of years, yes - it's possible. With all the circumstances being perfect, and enough snakes attempting the crossing, eventually some would make it, and then yes, they could survive the journey and become established.

Snakes have been found on islands where the only way they could have gotten there was to swim. Other islands at one time weren't islands, and the snakes were there long before the water covered some of the land, forming the actual islands. But one example is an island that suffered from a massive volcanic eruption. Many of it's snakes left before the eruption occurred and later, many of the snakes swam the long distance back to inhabit the island again.

Large Python Being Held By Biologists

Python Caught In Everglades National Park, Photo Credit Mike Rochford, U of F

FKV: These snakes seem pretty resilient, and they have the perfect habitat. Do you believe it's possible for us to completely eradicate python from the Everglades?

BR: That is most likely never going to happen. They have become fully established in the area. The best solutions we have are to stop them from being imported and to monitor and control the ones that are in captivity.

The U.S. Secretary of the Interior's recent announcement on the 4 injurious species is an important step in the right direction. Unfortunately, the very nature of the Everglades makes it very difficult to find, trap and kill these snakes. They are the master of camouflage and surprise. They are successful because they motionlessly sit and wait for their unsuspecting prey. If you can't see them, you can't catch and kill them, and this is what people don't understand. The Everglades, by their very nature, make it almost impossible to kill these snakes in any measurable numbers.

FKV: So they're here to stay.

BR: Yes, they're here to stay. However, at least now the numbers can't be added to, except through propagation. This means by trapping and baiting and using Judas snakes we could possibly reduce at least some of the numbers.

FKV: What is a Judas snake?

BR: A Judas snake is a male snake that has been anointed with the scent of a female in heat. The scent attracts other males in the area to where the Judas snake is held. The incoming males are then killed. Of course the best form of control is to prevent more from being introduced into the area. With the new measures being implemented, and the greater public awareness this announcement has caused, we can hopefully make the situation more manageable.

FKV: I've heard reports that pythons are in the Florida Keys. Is this correct?

BR: A few male pythons have been found in the Key Largo area. No one knows whether they migrated into the area in search of females, or whether they were released by owners into the region. We don't believe a breeding population has been established in the Key Largo area yet.

They also have been found on other islands in the Keys. Islamorada, Marathon, and a number in Key West as well - but again, we don't know how they got there.

FKV: Is it possible for them to swim across Florida Bay from the Everglades?

BR: Yes, it's possible. They do have a high tolerance for saltwater, and there are plenty of little islands along the way where they can rest and get water and food. Most likely though, the few snakes that have been found in the Keys were pets that were released.

FKV: People coming to vacation in this area may be concerned by the numbers of these snakes in the area. Do they pose a threat to humans?

BR: By their nature they are not normally a threat to humans. The fatalities that have been recorded have occurred with pythons who were kept as pets in people's homes. These are incidents where a snake got loose and killed a 2 year old child. Another where a man was found dead in his home after his python killed him. They do not consider humans a food source and so under normal circumstances at least, they wouldn't pose a threat.

FKV: What about their bite? I know they're not poisonous, but if you were bit by one, what about a serious infection from the bacteria in their mouths?

BR: Yes, a bite can be very serious. I know someone who was bit by a python. Their fangs are long and they curl back. He now has no feeling in two of his fingers because of the encounter.

FKV: What kind of a threat do they pose to the wildlife in the area?

BR: They are voracious eaters. They predominantly eat small mammals, and birds, but they also eat larger animals. A 72 pound deer was found inside one python, and a 6' alligator was found inside another. The real concern is that they're indiscriminate, and they're eating the endangered species as well. We have found the endangered wood stork inside python, as well as the endangered Key woodrat that lives in Key Largo. There's only a few hundred of these rats left and in several cases we've found pythons that had several rats inside them. This means they are actively eating these rare woodrats.

They're also eating the food that other larger predators rely on. The panther is an endangered species and the python is competing with it, for it's food supply. These snakes don't just compete with the panther, the panther is also a potential food source for them as well.

FKV: Can the alligators play an active role in helping us control and reduce the python population? What about shark, could they kill python?

Python Swimming in Florida Bay

Python Swimming In Florida Bay, Photo Credit Camp Walker

BR: Pythons have been seen attacking alligator and you'll find that alligators return the favor. With American crocodiles we have no evidence of predation, but it's unlikely that a python would kill a croc. As far as whether they'd be taken by sharks if they were swimming across Florida Bay to the Keys, I have no idea.

FKV: What about the small King Cobra population that is apparently breeding in the Everglades?

BR: I have never seen any evidence that they are actually there. I believe that's an urban myth.

FKV: So wrapping up this interview it's apparent that pythons are a part of our life in the Everglades. It's unfortunate that nothing was done about this sooner. I wonder why a law wasn't ever passed that limited importation to only one sex? That way any unwanted species released into the wild couldn't propagate, and eventually, the species would die off.

BR: Unfortunately no laws have ever been implemented for this sort of thing. We've always had more or less an 'open door' policy. Also, people aren't always responsible, or they don't understand the consequences of their actions.

FKV: And then you end up with this situation in the Everglades. It's a situation we now have to live with forever. Hopefully we'll find a way to control it. Thank you Bob for your time.

Additional Information And
Surprising Facts About Invasive Species

Further to the content of this interview, Mr. Reed provided us with additional information that had some surprising facts.

As of 2010, the pet trade was responsible for the highest percentage of invasions by a margin of just over 3:1.

Another of the more interesting invasive species facts is that even though it's been illegal to release snakes and other reptiles into the wild for some time, no one has ever been prosecuted.

Thankfully, under the new laws to be implemented in early 2012, this lack of prosecution will (or should) change and this will help prevent additional Everglades invasive snakes and other species from taking hold.

The new regulations will include penalties of up to 6 months in prison and a $5,000 fine for an individual, or $10,000 for an organization that breaks this Federal Rule.

Bob Reed has provided us with access to an especially interesting report that he co-authored with Gordon H. Rodda. It's one of the more informative invasive species articles, and even though it's lengthy it's well worth perusing when you have the time. The name of the report is "Giant Constrictors. Biological and Management Profiles and an Establishment Risk Assessment for Nine Large Species of Pythons, Anacondas and the Boa Constrictor".

Clicking on the link will take you to a page where you can read an abstract first. Then at the top left of the page you can click on "Complete Publication (PDF)" to review the full report.

This will give you greater understanding of the Everglades invasive snakes dilemma and the challenge we all face as we learn to manage it.

› Everglades Invasive Snakes


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