The Fascinating Mangrove Salt Marsh Snakes of Sanibel

Among the many amazing animals I saw on a recent visit to the Ding Darling National Wildlife Refuge on Sanibel Island (Fort Myers, Florida) was a beautifully red mangrove salt marsh snake. When I came across it, this one had grabbed a bewildered fish in its mouth and was working on turning it around to swallow.

Mangrove Marsh Snake

After a few minutes the snake did just that, gulping it down live. The gathering crowd was both fascinated and a little grossed out, though there seemed to be an even split between those rooting for the fish and the snake.

What is even more fascinating about the mangrove salt marsh snake – its scientific name is Nerodia clarkii compressicauda – is that while it lives in the roots of red mangroves in an estuarine environment, it doesn’t have any particular adaptations to living in sea water. Most aquatic snakes live in freshwater. There are fully marine sea snakes, but they live entirely in the ocean and are adapted to the salt water; in particular they have large organs designed specifically to excrete salt, which allows sea snakes to drink seawater.

Mangrove salt marsh snakes have no such organ so cannot drink seawater. Instead they get most of their fresh water intake from their food (like the poor fish above) and by drinking freshwater from temporary puddles that form in the sand or pockets of roots after rainstorms. Calling them aquatic is a bit of a misnomer: perhaps semi-aquatic is more accurate. But they also can be considered semi-arboreal in the sense that they spend much of their time on the proproots of red mangroves (Rhizophora mangle, which a particular favorite of mine because I had studied many years ago in Bermuda). Indeed, the one I saw was slithering around the shallows and over the prop roots with the fish in its mouth looking for a good place to eat. These snakes aren’t great swimmers so they hang out in shallow pools as the tide retreats and snap up trapped fish.

Another fascinating aspect of mangrove marsh snakes is their coloring. The one I saw was brilliant red but they can also appear as rather grayish with darker splotches and bands. Even odder, any given litter of mangrove marsh snakes could contain a mix of both colors; live-bearers, a litter could have up to 22 individuals. The gray phase allows them to hide in the leaf litter of mangrove trees while the red phase provides great camouflage for snakes resting on mangrove branches and prop roots.

The red phase I saw now rested after gorging down its meal, so I moved on to check out the rest of the mangrove trail. Along the way I saw another unique denison of the mangroves – a mangrove tree crab, most likely Aratus pisonii – clinging to a tree about 15 feet above the ground.

Mangrove Tree Crab

I saw a lot more both in the mangrove trail and the rest of the Ding Darling National Wildlife Refuge, but this snake having lunch was one of the most fascinating, and quite a thrill to capture on video.

David J. Kent is an avid science traveler and the author of Lincoln: The Man Who Saved America, now available. His previous books include Tesla: The Wizard of Electricity and Edison: The Inventor of the Modern World (both Fall River Press). He has also written two e-books: Nikola Tesla: Renewable Energy Ahead of Its Time and Abraham Lincoln and Nikola Tesla: Connected by Fate.

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6 thoughts on “The Fascinating Mangrove Salt Marsh Snakes of Sanibel

  1. I remembered seeing this and just showed your clip to a bunch of younger kids who were getting a lesson from some college students about animal adaptations. It was observed by the kids that that the snake has great camouflage among the roots of the trees and that a snake could probably move easily through them. Ever consider creating academic material?

    I’ll add that I didn’t know about the sea snakes’ ability to excrete salt before reading this.

    • Great to hear that kids are picking up on the science. As for creating academic material, it seems states are trying to strip science from academics these days.

      The sea salt thing is pretty cool. You’ve probably seen marine iguanas snort salt out of the nostrils. A lot of adaptations for living in seawater.

  2. I agree about the kids. Got me thinking back to a twisted pine tree observation from some 4th or 5th grade girls a few years back. Kids sometimes see and question things adults overlook. As for science in academics, I suspect that may change as manufacturers return to the US and find there’s no one left to hire. (Tesla’s “Gigafactory” lithium battery facility is presently having to import most of its labor from Japan).

    Marine iguanas… I just learned something else. 🙂

    • I hope that more people will be encouraged to going into science given the anti-science feeling of the current administration. Elon Musk certainly has intrigued a lot of people with his activities (the sending a Tesla roadster into space was brilliant). Luckily, kids are excited about new things and not biased until their parents teach them to be biased.

      Always happy to offer something new. Next up: grackles standing on one leg in a windstorm. 🙂

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