Danny Bryan is currently conducting a study at Center Hill Lake on a wildlife species most people do their best to avoid.
“Such a study on the timber rattlesnake has not been done before in Tennessee,” said Professor Bryan, who teaches biology at Cumberland University, in Lebanon, Tenn., “although studies have been done in other northern states. In 1999 or 2000, there was a coalition among several states, headed up by the U.S. Fish and Wildlife Service, working on a Conservation Action Plan for timber rattlesnakes. It looks like the intent of this plan is to see if and when the rattlesnake needs to be put on the threatened and endangered species list here.”
The Professor’s study may contribute to that decision by the state of Tennessee. According to Bryan, in 30 states but has been extirpated from three, is listed as endangered in seven, and is listed as threatened in five others. It is currently protected in five states. It is protected from harvest in Tennessee and is listed as in need of management.
The Corps of Engineers provided ideal habitat for the study.
“It would have been much more difficult for him to conduct the study without this ideal environment,” said Center Hill Park Ranger Stephen Beason. “This un-segmented land area is there because of the environmental policies of the Corps of Engineers. Our shoreline management plan does not permit development of this property.”
“Development is the biggest threat to rattlesnakes!” claimed Bryan. “When you get development, obviously there will be houses and when a snake moves through that property, the landowners are going to take that snake out. Snakes get pretty habitual and tend to follow the same trails.”
One of the Corps’ environmental principles calls for maintaining an environment in a healthy, diverse and sustainable condition necessary to support life.
Timber rattlesnakes can typically be found in bluff prairies and oak woodlands in relatively remote areas. They prefer rocky outcrops and open grassy areas with southerly exposures in the spring and fall. During the summer, they inhabit deciduous forests and open valleys. Rock fissures and crevices provide communal dens for overwintering.
Bryan regularly visits areas around the Lake to observe specimens which he locates with the aid of surgically implanted radio transmitters. Both Tennessee Technological University (TTU) in Cookeville and Tennessee Wildlife Resources Agency (TWRA) have supplied transmitters for the study.
He is monitoring more than a dozen specimens, some of which were provided by others and some he collected by scouring likely areas around Center Hill, to complete his dissertation for an Environmental Science Doctorate of Philosophy at TTU. A few were reported as a nuisance snake to TWRA. Sometimes likely specimens were delivered to the University by collectors who were aware of Bryan’s study.
Bryan, accompanied by Dr. Daniel Combs, TTU Biology Department Chair, made a visit to the wooded ridges around the Lake May 23 to collect data.
He first visited the den site of ‘Big Daddy’, a 64-inch-long male that typically lies in a favorite spot atop a rock.
“Right after he leaves the hibernaculum,” explained Bryan, “he will move to the top of a downed beech tree and use that for cover early in the season. When blackberries ripen, the snake then uses a power line right of way to move more than a mile to his favorite feeding spot near the blackberries. There he will feed on cotton rats.”
‘Big Daddy’ was not at home so the group then searched for and located ‘Peaches’ a 10-year-old 54-inch male, so named because of the color of his underside. Peaches easily blended with the leaves on which he lay coiled under a canopy of maple and hickory.
During each visit, Bryan takes meticulous notes that include details about the percent of overhead canopy, the types of trees near where the snake lies, and the exact location, based on a Global Positioning System. Those notes cover his observations over a three-year period.
“Snakebook number six is now full,” declared Bryan as he tucked it into a trouser pocket. The snake under observation lay motionless.
“He is using camouflage as his first line of defense,” explained Bryan. “Snakes feed primarily on chipmunks and gray squirrels at this time of year, but later this one will move, via the powerline right-of-way, to where the blackberries are ripening.”
He studies their range of movement, and all details related to habitat. He wants to know the length of active season for rattlesnakes in Tennessee.
“So what these snakes are doing,” mused Bryan, “does it parallel with what is going on farther north? I think we have a much longer active season. Scar, a big male I have been tracking, has not gone into hibernation yet before Thanksgiving.” He prefers to call them by names based on his observation, rather than numbers.
‘Yellow Mom’, a pregnant female with 14 rattles, lay coiled partially in sun 150 yards above the Center Hill Lake shoreline. Only a few days before, Bryan found her so near the shoreline that she was visible from his boat. He plans to collect her about August once the young are more fully developed. Such collection at this early stage of pregnancy might cause her body to absorb the newly developing offspring. She has been under his observation for more than three years, and has carried two different transmitters.
The doctoral student, who lives in Smithville, Tenn., has lost three study specimens to hawks, one to a deer, and one to exposure to cold temperatures.
His study will end late this fall once the last transmitter battery dies, probably when the snakes go into hibernation.
TWRA Wildlife Officer Mike Beaty pointed out that killing a rattlesnake is prohibited by Tennessee law.
“It is illegal to kill anything for which there is not an open season,” said Beaty. “The best thing to do, if you see one around where you live, is to just leave it alone. We have seen today that you can get inches away from a snake and it won’t bother you. The best thing to do is just walk away from it. People have this image of snakes as ‘aggressive’ but they are not, as we witnessed today at Center Hill.”
Bryan may not be finished, however, with his observation of the timber rattlesnake when his doctoral study is complete this fall. TWRA officials at the Catoosa Wildlife Management Area want him to conduct a similar study of the reptile species at that location.
Current Status
The state of Wisconsin listed the timber rattlesnake as a "Protected Wild Animal" in 1998. This designation makes it illegal to take or kill this species there except under the following conditions: A timber rattlesnake may be killed in an immediate life-threatening situation involving human life or domestic animals. This species or its parts may not be possessed.
This snake is also listed as a "Species of Special Concern" because of its low numbers. There is sentiment that current population trends warrant a federal listing. The timber rattlesnake is listed as a threatened species in Illinois and Minnesota.
Existing Threats
Increased residential development has led to increased human/timber rattlesnake encounters, resulting in the loss of snakes and their habitats. The collection of timber rattlesnakes for hides (used for hat bands, belts, and boots), meat, venom, and artifacts (rattles and freeze dried snake heads) has continued to deplete already threatened populations up through 1997.
Habits
Timber rattlers begin emerging from hibernation in April to early May, depending on temperatures, to take advantage of the warm spring sun. They will remain close to the den site until temperatures become consistently warm and then they venture out into the surrounding landscape. Pregnant females will usually remain around denning sites, basking in the sun to speed the development of there young. Males, non-gravid females and immature rattlesnakes will return to the den site in early fall and remain active into October. They are both diurnal (active during the day) and nocturnal (active after dark) in the summer, but only diurnal in the spring and fall.
Timber rattlesnakes are experts at climbing along rocky ledges and scaling steep bluffs, and are also able to swim. Rattlesnakes typically crawl with the tip of their tail and rattle held perpendicular to the ground.
Ecology
The Timber Rattlesnake is highly dependent on the existence of suitable winter denning habitat. While these areas do vary across the timber's geographic range, they are generally associated with rocky outcroppings or talus slopes where crevices can afford the snakes protection over the winter months. In some areas, timbers may also hibernate in rodent burrows, or below vegetative root systems. These denning sites are typically found in forested areas, including forested riparian zones. The diet of the Timber Rattlesnake consists mostly of rodents, and common prey includes chipmunks, mice, and squirrels. The species relies heavily on sense of smell, and their dietary tactic involves lying motionless in animal runways to ambush their prey. Timber Rattlesnakes are a long-lived species, often living to 20 years or more. An interesting fact about Timber Rattlesnakes is that they will return to the same den year after year in order to hibernate through the winter months.
Threats and Management Issues
Habitat loss and fragmentation are the chief threats facing Timber Rattlesnakes. While at one time the species was considered relatively ubiquitous across its range, most surviving populations today are considerably isolated. Human persecution and harvesting have also had devastating effects on this species. Timber Rattlesnakes are known to den communally, and in the same location year after year. Because of this, den sites are particularly sensitive areas and should be a high priority for protection. In some areas, Timber Rattlesnake levels have dropped to critically low levels as a result of dens being abused and used as activity centers from which to collect snakes. While the Timber Rattlesnake is poisonous, it is not an aggressive species. In fact, the majority of documented bites have occurred while individuals were trying to pick the snakes up.