Friday, February 26, 2010

Thoughts on Cold Weather and Invasive Snakes.

The cold weather experienced in southern Florida has damaged crops causing economic damage to orange growers. It has also been proposed that the cold weather would solve the python problem. A January 1, 2010 Miami Herald article by Robert Samuels states,
"Scientists have waited for years for this moment. They are hoping that the extended, freakishly bitter cold just might accomplish what trappers have been unable to do: thin the population of pythons and other invaders running roughshod over the fragile environment and native species. Or at least slow their explosive growth."

The same article quotes University Florida Wildlife scientist Frank Mazzotti saying,  "Today has been what I would consider a game changer...The pythons are going to be stunned by this kind of weather."

Other articles report 50% of the Burmese Python found were dead, describe the invasive Green Iguana as falling out of trees, and state that many invasive freshwater fish have died.

The cold snap undoubtedly brought about a die-off of individual animals that were exposed to the cold but some individuals will have been in shelters where they would be protected from the cold. They may have learned how to survive the cold weather. But, some of them, maybe just a few, have a physiology that allows them to better withstand the cold. These snakes will survive, reproduce, and leave offspring that are also able to survive cold snaps. Overtime the populations of invasive constricting snakes will adapt to the local climate that includes the occasional cold front that sags into southern Florida. Just as bacteria become resistant to antibiotics, snake populations will become resistant to cold. If the Burmese Python, African Python, Boa Constrictor populations are large enough they too will likely become cold resistant.  Natural selection works this way. It should not be a surprise to any biologist.

4 comments:

  1. I agree with you, but I think the first surge in B. Python snake populations to be found will be in the multitude of housing projects surrounding the glades. What better place to wait out a freeze than under a warm house, in a heated garage with a open back door, a garden shed?
    Before they were being found in these communities in larger numbers around the glades, (this includes retics, boas) always assumed escaped or released pets but....

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  2. I agree. Human habitations are likely to be places where the snakes can find food, shelter, and heat.Abandoned houses and pets will increase the available habitat and food supply.

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  3. this is all true, but natural selection can only work at the speed of reproduction. Large constrictors have a long lag time between birth and reproduction; some species take 20 years to reach sexual maturity.

    Has anyone looked at the incidence rate of snakes in human habitations for the cold snap compared to previous measurements?

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  4. Jennifer, I don't know if anyone has looked at habitats used in Florida. However, giant snakes do mature more rapidly than 20 years. There is a report of a male bivittatus being sexually mature at 1.7 m (this snake could have been about two years in captivity). Females are reported to mature at 2.6 m (probably 2.5 years for a well fed captive, may be 3 or 4 years for a wild individual. Bill Branch reported female P. sebae mature at 2.5 m. Rich Shine estimates female retics mature in 3 years in captivity, and Jack Cox suggests 5 years. The Barkers also report that captive male retics mature in 18 to 24 months and females in 30 to 36 months. So, yes, giant snakes won't become cold resistant as fast as bacteria become resistant to antibiotics but in two decades there will be four or more generations of snakes. Maturity seems to be greatly dependent on food availability.

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