Monday, October 25, 2010
Autumnal Movements of Cottonmouths?
The Cottonmouth (Agkistrodon piscivorus)is a widely distributed and fairly well-known venomous snake in Florida. They are usually found in or very near to water. The first Cottomouth I ever saw was a very large specimen swimming in a wetland at Back Bay National Wildlife Refuge near Virginia Beach, Virginia. There the animal is at the extreme northern limit of its range in the United States (they do not occur north of the mouth of the Chesapeake Bay.
Since that first sighting and outside of Florida, I have been fortunate enough to see this fantastic reptile at Moore's Creek National Battlefield in southern North Carolina, underneath a bridge on Pee Dee National Wildlife Refuge in southern North Carolina, in the parking lot of the Hilton Garden Inn at Hilton Head, South Carolina, one with a particularly nasty disposition on Yazoo National Wildlife Refuge, Mississippi, and at least three of them floating around in a cypress-dominated wetland near Lafayette, Louisiana.
In Florida I have seen Cottonmouth's from Escambia County (Pensacola) south through most of the state to Dade County (Miami). Today was the first time I was ever able to see three Cottonmouth's in the state in one day. Unfortunately two were dead and I ran over the third one and killed it with my car.
About noon today while driving on the "canopy road" portion of 47th street enroute to the British pub for lunch, I had an instantaneous look at a Cottonmouth attempting to cross the road. Unfortunately for him three things were working against him from the start. First, the back of the animal was black, 2) it was crossing black asphalt, and 3) it chose to do this in the shade of a very large live oak tree. There is a concept in biology of protective coloration where an animal blends in with the color of its surroundings for protection. Think of a chameleon for instance. Well, the Cottonmouth's protective back color would have worked on the black asphalt and in the shade of the oak tree except that my car was moving through the same space as him and ....splat. I got out of the car and went to check on the snake's status. It was a 2 1/2 footer and it was quite dead. As I looked at it I had to ask what in hell I was doing. Was I going to take it to a veterinarian if it was still alive?
Later in the afternoon as I was leaving home to go on a 12-mile bicycle ride I found a dead Cottonmouth in the drive leading into the condo development where I live. It was pointed toward the wetland behind my house. Then as I pedaled out on to Honore Avenue, I found a third Cottonmouth lying dead along the road. It was pointed toward a small wetland in a conservancy area adjacent to Honore Avenue. Both the one in my yard and the one on the main street were about 2 feet long.
As I pedalled away from the third dead Cottonmouth of the day I started to wonder why it was that I saw three of them in a day, all within 1 1/2 miles of each other. Yet for all of 2010 until now I had seen only 1 Cottonmouth in this part of Sarasota - and it was in the forested wetland adjacent to Honore where I found the dead one today.
Most people are familiar with the migrations of some animals like the Arctic Tern that nests in the higher latitudes of the northern hemisphere, and winters off of Antarctica. Some people claim that they do a 20,000 mile roundtrip migration each year (and all that to get laid just once...imagine). And certainly most people are familiar with the migration of American Robins complete with the old adage about the first Robin of spring etc. These animals move tremendous distances each year.
At the same time there are other species of animals that have much shorter movements that are possibly a "migration" but more correctly a seasonal movement. Hummingbirds in tropical mountains are known for these sorts of movements as are birds like the Brown-capped Rosy Finch in the Colorado Rockies. American Elk (more correctly known as Wapiti) are well-known for altitudinal movements in the Rocky Mountains, most famously toward the National Elk Refuge in northwestern Wyoming.
I thought about those sorts of movements in other animals and wondered if that is not the same thing that was going on now with Cottonmouths and, unfortunately, what is making them more vulnerable to being killed on the road.
My first job with the US Fish and Wildlife Service was as an Ascertainment Biologist in the regional office in Minneapolis. There a group of four of us (this was before the over-used word "team" became vogue) evaluated lands that had been proposed to the Service for acquisition and addition to the National Wildlife Refuge system. Our mission was unique for the Service at that time because we were specifically barred from looking at lands that only or primarily benefited waterfowl (a HUGE paradigm shift for the agency then). Our area of responsibility included Minnesota, Wisconsin, Michigan, Ohio, Indiana, and Illinois.
One of the areas nominated to us was a lowland forest with rocky outcroppings in southern Illinois near Cairo, that later became known as Cypress Creek National Wildlife Refuge. The reason Cypress Creek was nominated (and later acquired) was because of its importance as a wintering area for venomous snakes including Canebrake Rattlesnake, Copperhead, and Cottonmouth. We flew into St. Louis, Missouri 33 years ago today so we could go down to Cypress Creek and determine if it was suitable for Service acquisition. I remember the trip in there like it was yesterday - I had never seen any venomous snake at that point in my life and I was petrified that I would be run over by all manner of snakes. We never saw a single one during our day checking out Cypress Creek - the snakes were already "holed up" for the winter. However the experience taught me that snakes make seasonal movements from a preferred habitat to a more "stable" habitat to live out the winter in torpor. At Cypress Creek, venomous snakes migrated from miles around to spend the winter in rocky outcroppings near the center of the lands we evaluated.
If venomous snakes including Cottonmouth's make seasonal movements at more northerly latitudes like southern Illinois, why wouldn't they do the same thing in Florida? The timing of them "holing up" in southern Illinois is uncannily similar to the apparent "movement" I noticed here in coastal Florida today. A quick search of the online literature gave no hint of any sort of seasonal movements in Cottonmouths in this state but who knows. Maybe nobody was interested enough to look into it. With all the Cottonmouth's here and all the habitat remaining for them it might be another thing to do in retirement that may some day have some value to a biologist somewhere. Maybe I'll become a herpetologist now?
On another note...I am vehemently opposed to killing snakes just because they are snakes. Its foolish, our fear of snakes is based in folklore, and each time someone does it they take one more chink out of mother nature's armada. I feel badly that I killed that beautiful Cottonmouth today. I wish I hadn't. More than one time I have stopped my car and gotten out and chewed out the Cheney of people who were about to kill snakes along side a road. There is no excuse for it. After all, humans are about 1000 times larger than any snake in the United States. Give them a break - they were here first.