Home | Amphibians | Cold Snap in Florida Affects Introduced (i.e. Burmese Pythons) and Native Herps

Cold Snap in Florida Affects Introduced (i.e. Burmese Pythons) and Native Herps

Gator and PythonI’ve received a number of questions lately from herp enthusiasts (and “regular people”!) who have come across cold-stunned reptiles and amphibians in Florida.  Cuban Knight Anoles, Green Tree Frogs and many other species have been severely impacted by the record-breaking cold weather.

Burmese Pythons

A colleague’s comment on cold weather and Florida’s introduced Burmese Pythons brought to mind an incident that occurred several years ago.  A friend of mine stopped into a coffee shop near Florida City and was surprised to see the skins of 14 large Burmese Pythons tacked to the wall.  She learned that the shop’s owner had captured all along one road on a single warm morning following a cold snap.  Herpetologists also know that such times are ideal for collecting, as snakes flock to roads to take advantage of the warm pavement and access to sun.

In parts of its native range, the Burmese Python actually encounters quite cool winters, and is known to hibernate.  In fact, captives rarely breed unless stimulated by a cooling-off period.  Florida’s unusually cold weather will likely not cause many mortalities, but, as illustrated above, may render the snakes more vulnerable to people and predators.

Other Introduced Species

Successful invasive species are hardy by nature, but those from very warm habitats will suffer from exposure to low temperatures.  I’ve had several reports of Cuban Knight Anoles that have been found alive but which remain lethargic even when warmed up.  What likely happens is that the immune system becomes depressed, leaving the animal open to attack by pathogens.

Further north, conditions in winter are harsher.  An introduced population of Barking Treefrogs, which normally range to Virginia, persisted in southern New Jersey for several years but died off one extra-cold winter.  Italian Wall Lizards (Podarcis sicula) are well-established in NYC and weather most winters easily, but experience high mortality during prolonged freezes.

Crocodiles and Alligators

One native animal of concern is the American Crocodile, which reaches the northernmost limits of its range in southern Florida – animals at the extreme edges of their ranges are at risk during severe weather.  However, Florida’s crocs have take steps to solve this problem on their own.  Most of the state’s population has moved into the 90+ F waters of the Turkey Point Power Plant’s canals.  Years ago I toured the area and was surprised to see such a large, vigorous breeding population.

Florida’s other native crocodilian, the American Alligator, should be okay as well.  Alligators range as far north as southern Virginia, where they inhabit lakes that sometimes become ice-bound.  They utilize a very unique strategy at these times to survive, lying relatively dormant in shallow water with their snouts protruding through a hole in the ice – not what most expect of a “tropical” creature!

Other Native Species

Many natives with large ranges differ in their tolerance to the cold.  For example, Green Anoles from southern Florida cannot survive the temperatures that are routinely tolerated by the same species in northern Florida.  This has important conservation implications – someone who picks up an Eastern Box Turtle in North Carolina and releases in NY may be consigning it to an early demise.

Fishes on Tropical Fish Farms, native fishes and crayfishes have also expired in record numbers this year.  Please check out my recent posts on Twitter for links to related articles.

Further Reading

An article and video on cold-stunned sea turtles in Florida is posted here.

Recent stories covering the stunned Green Iguanas can be read here and here.



  1. avatar

    The cold snaps that lasted for two weeks killed 90% of Iguanas in Ft lauderdale from what I can tell.

    Brown Anoles were hurt less but still suffered a devastating blow to population numbers.

    Green Anoles/ Who knows, you can hardley find one now a days.

    Cuban Tree frogs and Cuban anoles were also wiped out, I have found dead specimens only, no living., fwiw.

    • avatar

      Hello, Frank Indiviglio here.

      Thanks for your interest in our blog and for writing in with your observations. I’m interested to see if such a drastic blow selects for cold-hearty individuals. Those that survived may have just found good places to stay, but there’s always the chance that genetics were involved…may wind up with a more cold tolerant population in a few generations. As you note, Green Anoles declining already, possibly due to some of the introduced species. Has anyone compiled any statistics – i.e. number of green iguanas found?

      Good luck and please keep me posted.

      Best regards, Frank Indiviglio.

  2. avatar

    Hey Frank, i’m interested in one specific thing you said here:

    “Italian Wall Lizards (Podarcis sicula) are well-established in NYC and weather most winters easily, but experience high mortality during prolonged freezes.”

    where’d you get that from?

    • avatar

      Hello Russell, Frank Indiviglio here.

      Thanks for your interest in our blog. This by way of a former co-worker at the Bronx Zoo, who lived in Nassau County (Franklin Sq?). His neighborhood had a sizable population, and a neighbor of his spent a great deal of time observing the lizards. He related finding dead lizards after sudden cold snaps in the fall, and also seeing noticeably fewer animals after especially cold winters. He seemed, according to my co-worker, to have a good handle on the status of those that lived in his yard and around his house., but entirely anecdotal.

      A small group is also established in the Gelada Baboon Exhibit at the Bronx Zoo, or was as of 4-5 years ago; I rarely saw any after mid-September; the regular keeper there reported the same – they seemed to go into dormancy before the really cold weather set in.

      Best regards, Frank Indiviglio.

  3. avatar
    Name Jay Kiessling

    “In parts of its native range, the Burmese Python actually encounters quite cool winters, and is known to hibernate. In fact, captives rarely breed unless stimulated by a cooling-off period.”
    I’m not sure where you got that information that they rarely breed w/out coolong, but I’ve kept pythons for 40 years, and have NEVER found that to be the case.

    • avatar

      Hello Jay, Frank Indiviglio here.

      Thanks for your interest in our blog. The variance in what we’ve observed may be due to the origin of the animals in question – species with large natural ranges may exhibit differences in their breeding biology in different parts of the range. Also, long-lived animals may sometimes alter reproductive behavior over time in accordance with captive conditions. In terms of reproduction, I’ve observed this more commonly among mammals; some long-lived reptiles do alter activity patterns I response to captive conditions over time – I’d need to check notes re reproduction but would not be surprised if the same held true.

      Best regards, Frank Indiviglio.

  4. avatar

    so the observation that wall lizards experience die-offs in harsh winters actually came from Nassau County, not NYC. the seasonal dormancy you observed at the Zoo is similar to what they do in Italy, altho they are sometimes active on warm days in January, which they never do that here, except in my greenhouse. I suspect that they hibernate pretty deeply here, but i have seen wall lizards with frost-bitten toe loss. In fact, Behler once accused me of starting the Bronx Zoo population, since he know i worked with Podarcis and that I toe-clipped lizards for identification. I’m innocent, i’ve never started a new population.

    • avatar

      Hello Rusell, Frank Indiviglio here.

      Yes, Nassau – sorry for the confusion.

      Sounds like John alright! – the stories I could tell…

      Thanks for the info; if you have a chance, I’d be interested to know the average length of their active period in Nassau. I recall you identified Podarcis as the prey of a pair of Kestrels nesting in Manhattan last spring – seems they were catching them regularly; very interesting.

      Good luck and please keep me posted.

      Best regards, Frank Indiviglio.

  5. avatar

    Hi I live in the Southern Georgia border with Florida, this winter has been very harsh, most of the Green Anoles that we have are hidding inside a closed umbrella we have in our patio.
    But I found one inside the house that was trapped in a spider web, we saved him but he lost part of his tail in the process. My husband put back him outside, the next day he was in the same spot and was not moving at all.
    I picked him up and saw that he was slowly breathing, so I took him inside, put him by the light and waited.
    In the next couple of days, I opened his mouth and gave him some green lettuce chopped finelly. Also gave him drops of water, he begun to move around and turn colors slowly. This was 3 weeks ago, the little guy now moves around and does not go anywhere but around my desk. He lays on a rock that I have on a shelve and up from there he watches me in between naps. What concerns me is that he does not eat, or drink on his own. I leave the lettuce and water but he is not interested, he does sleep most of the time. I love to see him watching everything from that spot and of course he is warm.
    I am glad I didn’t put him back outside as we still have very cold nights and days.
    So I am asking you, is he going to be ok eating and drinking so little? I feel bad when I have to open his mouth because he is a little guy, he seems fine to me and happy and cute. Please advice, thanks.

    • avatar

      Hello Nina, Frank Indiviglio here.

      Thanks for your interest in our blog and the most interesting story. I’m glad to learn of the site that the anoles chose to pass the cold snap, and also of your kindness to the distressed individual.

      Anoles in Georgia/N. Fla can withstand cold weather better than individuals of the same species in south Fla, although there are some deaths during harsh winters. I’m guessing that most of those under your umbrella will be fine.

      The one you have taken in poses a bit of a problem. Their activity is largely controlled by an “internal clock”, and so even if kept warm the lizard will likely not feed (they eat insects only, so please do not force-feed lettuce; the small amount given so far will do no harm). Usually, they will do fine if kept warm but without food, but to be safe its best to keep it at average room temperatures, not under a heat light or such. Water is important…anoles will not drink from a bowl, but rather lap drops of water from plants, etc. A light daily misting of warm water should suffice.

      It’s hard to tell by looks alone, but the lizard is probably stressed by being kept in an open situation (its not reacting because its metabolism is in “winter mode”). It would be best to house it in a plastic terrarium furnished with some sticks/plants bearing leaves or artificial plants. In this situation it will find a secure retreat and will more likely lap up water. I suggest putting the lizard back with the others on the first somewhat mild day – keeping it until spring would pose more of a risk than would allowing it re-adjust to the patio. The tail will re-grow as soon as the weather changes and feeding commences.

      Congrats on your fine efforts…good luck, enjoy and please keep me posted,

      Best regards, Frank Indiviglio.

  6. avatar

    I’m afraid the range information you have is for the closely related Indian python–not the Burmese python, which is strictly a tropical weather animal. Burmese do not experience cold temperatures in their natural range. Don’t make the same mistake USGS did, and lump them in with the Indian python (which isn’t even being imported). We should expect temperatures like this to kill most Burmese–survivors may succumb to cold-related injuries or respiratory infections. These animals do not have the instincts to seek out shelter when the weather is dangerously cold, unlike their cousins.

    • avatar

      Hello Donna, Frank Indiviglio here.

      Thanks for your interest in our blog.

      There is quite a bit of misleading information floating about these days, but actually I was referring to the Burmese Python, P. molurus bivittatus (or P. bivittatus per some authorities, i.e. Am. Museum of Nat. History). It is sympatric with the Indian Python, P. m. molurus in certain parts of the range, which adds to the confusion.

      The Burmese Python does experience quite cold temperatures in the northern parts of its range (S. Nepal, NE India, Bangladesh, N. Myanmar) and does enter hibernation/brumation at such times. Even within warmer regions to the south, high altitude populations may do the same (a co-worker and others have found them near Tam Dao, Vietnam, at altitudes of 1,200 feet ASL).

      Whether or not those populations dwelling in the tropics have the ability to withstand cold temperatures has not been fully investigated.

      Best regards, Frank Indiviglio.

  7. avatar

    I believe the Savannah River Site Ecology Lab in the middle part of South Carolina (on the border with Georgia) released about a dozen Burmese Pythons into an artificial (but outside) habitat last fall to see if they could withstand a South Carolina winter. LOL….Of course it would happen to be one of the coldest winters on record but I can only imagine what the result of their “experiment” was.
    Nina, Im glad your green anoles did fine. I wonder about the introduced brown anoles that have made it into Georgia. I notice them every time I visit the islands in south Georgia. They probably took a hit big time but Id imagine it is only a matter of time for them to re-populate given the tranport of landscape material between there and florida.

    • avatar

      Hello Mike, Frank Indiviglio here.

      Thanks for your interest in our blog.

      Some great herp research has come out of Savannah, I’ll look into the Burmese Python work, thanks. I agree re the Brown Anoles…sometimes stresses such as this past winter tend to concentrate the animals with favorable genes, helping rather than hurting the species in the long run by assuring that cold-tolerant individuals will be likely to breed with one another.

      Good luck and please keep me posted.

      Best regards, Frank Indiviglio.

  8. avatar

    Thank you Frank and Mike, the outcome has been an interesting one, like I said lots of Anoles were hiding under the umbrella, and the one I had in the house was the most amazing experience for me. Yes, it was not eating the lettuce, to give it water I had to do it with my finger drop by drop and I found out that he liked bananas, from my hand only. He would watched the laptop monitor as the images changed. Anyway, one day it was warm outside and all the anoles were bathing in the sun, so I thougth it is time for me to let him go. He happily hopped away, the problem came later we had more cold days and I was so worried he would not make it. I saw lots of them dead, with frozen toes. Then as it got warmer, I found him hiding under another umblella that was laying on the floor. As the days went by lots of Anoles would peak out while the sun was warm. The funny thing is that now, they are all gone, and only two males are left (one if them was the one I saved) the other day they were fighting, they grabed each other by the mouth, until one can’t take it anymore and leaves, each has one side of the deck rail. I have not seen any other Anoles around, even though Anoles turned dark grey when they get stressed out I think you may be reffering to the other ones I have seen around ugly things they are much larger than the Anoles, brown, blue and orange in color maybe some white too, don’t know if this is the right spelling but my husband says they are skenkes. Around this plantation, we have all kind of wild danger life, when it begins to get warm, Water Moccasins are everywhere and so are Rattle snakes and gators too….iRed foxes and grey foxes too it is pretty wild out here. Can’t really take walks to enjoy the scenery, cause there is always something deadly that comes up!!!!! Thanks again.

    • avatar

      Hello Nina, Frank Indiviglio here.

      Thanks for the update; glad all your efforts paid off!

      Enjoy, and please keep me posted.

      Best regards, Frank Indiviglio.

  9. avatar

    Burmese Pythons make really good pets as they usually have a very placid nature. You do find a few individuals who are exceptions to the rule, but generally they are docile. They do however require a lot of handling and can reach a large size and should not be handled alone once they have reached their full potential.

    • avatar

      Hello Dalesh, Frank Indiviglio here.

      Thanks for your interest in our blog.

      Unfortunately, there have been a number of tragedies here in the US involving Burmese Pythons kept as pets; While there certainly may be a rare few private hobbyists with the space and experience to deal with an adult, I feel they are best left to zoos.

      Good luck and please keep me posted.

      Best regards, Frank Indiviglio.

  10. avatar

    Hi Frank,

    I live in a western part of brooklyn, NY, My family spotted wall lizards in our back yard in August 2009. Slowly we are seeing more since than. My son & Husband say there back (April 12, 2011) and this time with more smaller ones. What we could see now, the harsh winter didn’t cause die-offs, I don’t think Brooklyn is any different than Nassau so maybe they found a nice spot to go into dormancy.

    I have a Question, We count between 12 to 25 lizards running around from day to day in the summer. How big will this small population be in five years?

    • avatar

      Hello Nancy, Frank Indiviglio here.

      Thanks for the most interesting comment; I’m happy to have this new information on Wall Lizards in NYC. Hibernation success seems to depend upon how deep below the ground they can get. They do not dig well, so each population must find naturally occurring tunnels or other ways to get below the frost line; or perhaps in sandy soil they are able to create deep burrows.

      As they are introduced, there really is no way to predict population increases; in some parts of Nassau they seem to spread rapidly; in other habitats that would seem to be ideal they barely hold their own. Please take notes if you can – anything you might learn would be most useful and appreciated by a colleague of mine who studies them in detail.

      Please let me know if you need any further information. Good luck, enjoy and please keep me posted.

      Best regards, Frank Indiviglio.

  11. avatar

    Hello Frank,

    I don’t know if this is good info for you. But the Wall lizards have been out since feb 19th. My son says it’s way to early for them to be out but they are.

    • avatar

      Hello Nancy,

      Thank you…very interesting indeed! Is this in NYC? I live here, but have not been to any Wall Lizard sites yet, but that is the earliest I’ve heard. On Feb 17th of this year, I found the Common Snapping Turtle pictured in this article (with my 4 yr old nephew) out and about in a small pond just off the Hudson, in N. NJ…also an early record for me. I checked a site for spring peepers and spotted salamanders tonight, but no luck; they should move soon. Fortunately, these and other hardy species are usually able to sink right back into dormancy when needed; they are only rarely caught by surprise.

      Any additional info on the lizards would be appreciated, and I can forward to a local herpetologist who has done a great deal of work with them. Good luck, enjoy and please keep me posted.

      Best regards, Frank Indiviglio.

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About Frank Indiviglio

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Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.
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