Snakes on Our Barrier Islands

Over the last two years I have been surveying snakes in a local community on Perdido Key.  The residents were concerned about the number of cottonmouths they were seeing and wanted some advice on how to handle the situation.  Many are surprised by the number of cottonmouths living on barrier islands, we think of them as “swamp” residents.  But they are here, along with several other species, some of which are venomous.  Let’s look at some that have been reported over the years.

In the classic text Handbook of Reptiles and Amphibians of Florida; Part One – Snakes (published in 1981), Ray and Patricia Ashton mention nine species found on coastal dunes or marshes.  They did not consider any of them common and listed the cottonmouth as rare – they seem to be more common today.  In a more recent publication (Snakes of the Southeast, 2005) Whit Gibbons and Michael Dorcas echo what the Ashton’s published but did add a few more species, many of which I have found as well.  Their list brings the total to 15 species.  I have frequently seen four other species in Gulf Breeze and Big Lagoon State Park that neither publication included, but I will since they are close to the islands – this brings the total 19 species that residents could encounter.

 

Leading us off is the one most are concerned about – the Eastern Cottonmouth (Agkistrodon piscivorous).  Though listed as “rare” by the Ashton’s, encounters on both Pensacola Beach and Perdido Key are becoming common.  There is more than one subspecies of this snake – the eastern cottonmouth is the local one – and that the water moccasin and cottonmouth are one in the same snake.  This snake can reach 74 inches in length (6ft).  They are often confused with their cousin the copperhead (Agkistrodon contorix).  Both begin life in a “copper” color phase and with a luminescent green-tipped tail.  But at they grow, the cottonmouth becomes darker in color (sometimes becoming completely black) while the copperhead remains “copper”.  The cottonmouth also has a “mask” across its eyes that the copperhead lacks.  Believe it or not, the cottonmouth is not inclined to bite.  When disturbed they will vibrate their tail, open their mouth showing the “cottonmouth” and displaying their fangs, and swiveling their head warning you to back off.  Attacking, or chasing, rarely happens.  I find them basking in the open in the mornings and seeking cover the rest of the day.  Turning over boards (using a rake – do not use your hand) I find them coiled trying to hide.  MOST of the ones I find are juveniles.  These are opportunistic feeders – eating almost any animal but preferring fish.  They hunt at night.  Breeding takes place in spring and fall.  The females give live birth in summer.  As mentioned earlier, they seem to be becoming more common on our islands.

 

This year, while surveying for cottonmouths, I encountered numerous Eastern Coachwhips (Masticophis flagellum).  These long slender snakes can reach lengths of 102” (8ft.), move very fast across the ground – often with their heads raised like a cobra – and, even though nonvenomous, will bite aggressively.  They get their name from their coloration.  They have a dark brown head and neck and a tan colored body – resemble an old coachwhip.  They like dune environments and are excellent climbers.  They consume lizards, small birds and mammals, and even other small snakes.  They are most active during the daylight, but I usually find them beneath boards and other debris hiding.  They have always been on the islands but encountered more often this past year.  They lay eggs and do so in summer.

 

Their close cousin, the Southern Black Racer (Coluber constricta) is very similar but a beautiful dark black color.  They can reach lengths of 70” (6ft.) and are also very fast.  Like their cousin, they are nonvenomous but bite aggressively – often vibrating their tail like cottonmouths warning you to stay back.  They are beneficial controlling amphibian, reptile, and mammalian animals.  They are also summer egg layers.

There are a few freshwater snakes that, like the cottonmouth do not like saltwater, but could be found on the islands.  These are in the genus Nerodia and are nonvenomous.  There are two species (the Midland and Banded water snakes) that could be found here.  They resemble cottonmouths in size and color and are often confused with them.  They differ in that they have vertical dark stripes running across their jaws and have a round pupil.  Though nonvenomous, they will bite aggressively.  One member of the Nerodia group is the Gulf Coast Salt Marsh Snake (Nerodia clarkii clarkii).  This snake does like saltwater and is found in the brackish salt marshes on the island.  It is dark in color with four longitudinal stripes, two are yellow and two are a dull brown color.  It only reaches a length of 36” (3ft.), is nocturnal, and feeds on estuarine fish and invertebrates.

Other species that the guides mention, or I have seen, are the small Crowned Snake, Southern Hognose, Pine Snake, Pine Woods Snake, and the Rough Green Snake.  I will mention here species I have seen in either Gulf Breeze or Big Lagoon State Park that COULD be found on the island:  Eastern Coral Snake, Eastern Garter Snake, Pigmy Rattlesnake, Eastern Hognose, and the Corn Snake (also called the Red Rat Snake).  Only two of these (Eastern Coral and Pigmy) are venomous.

 

Last, but not least, is the Eastern Diamondback Rattlesnake (Crotolus adamateus).  This is the largest venomous snake in the United States, reaching 96” (8ft.).  It is a diurnal hunter consuming primarily small mammals, though large ones can take rabbits.  They prefer the dry areas of the island where cover is good.  Palmettos, Pine trees, and along the edge of wetlands are their favorite haunts.  Despite their preference for dry sandy environments, they – like all snakes – are good swimmers and large rattlesnakes have been seen swimming across Santa Rosa Sound and Big Lagoon.  They tend to rattle before you get too close and you should yield to this animal.  The have an impressive strike range, 33% of their body length, you should give these guys a wide berth.  I have come across several that never rattled, I just happen to see them.  Again, give them plenty of room when walking by.

It is understandable that people are nervous about snakes being in popular vacation spots, but honestly… they really do not like to be around people.  We are trouble for them and they know it.  Most encounters are in the more natural areas of the islands.  Staying on marked trails and open areas, where you can see them – and be sure to look down while walking, you should see them and avoid trouble.  For more questions on local snakes, contact me at the county extension office.

 

References

 

Ashton, R.E., P.S. Ashton. 1981. Handbook of Reptiles and Amphibians of Florida; Part One – Snakes. Windward Publishing, Miami FL. Pp.176.

 

Gibbons, W., M. Dorcas. 2005. Snakes of the Southeast. University of Georgia Press, Athens GA. Pp. 253.