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Presentation provides better understanding of area’s timber rattlesnakes

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Iowa Department of Natural Resources Conservation Officer Burt Walters recently gave a presentation on timber rattlesnakes. The event even featured a live snake, which Walters said he found two weeks prior and would be on display at the Driftless Area Education and Visitor Center in Lansing through the summer. (Photos by Audrey Posten)

Timber rattlesnakes are large, heavy bodied snakes identifiable by their black chevron markings with a white outline and typically bright, golden body. However, they are darker and more grayish in color when preparing to shed, which can be up to three times in a good year. They also gain a new segment of rattles each time they shed their skin.

By Audrey Posten, Times-Register

 

“This one came out of the woods one or two weeks ago,” said Iowa Department of Natural Resources Conservation Officer Burt Walters, as he watched a timber rattlesnake slither across the floor a safe distance from his booted feet. He used a stick to help guide the younger male rattler, which was well short of the 75-inch maximum length the snakes can reach.

 

“You can see he’s not aggressive and seeking me out,” Walters told those gathered for a June 21 presentation in McGregor. He was one of a series of speakers organized last month by the new Convention Conference Community Center, formerly McGregor’s Methodist Church.

 

According to Walters, the timber rattlesnake’s temperament is one of the biggest misconceptions about the creature, which is one of 30 snake species in the state and one of four that is venomous. It’s the only venomous species living in northeast Iowa. 

 

“A timber rattlesnake is the most docile of all the venomous snakes out there,” he explained. “They want nothing to do with humans, and if you leave them alone, they will crawl away from you.”

 

Walters would know. He’s worked for the Iowa DNR since 1997 and led snake programs since the early 1990s.

 

In 1999, through public education efforts from himself and another conservation officer, timber rattlesnakes were protected in 14 of the state’s 99 counties, including Clayton.

 

“We were doing surveys and found we were losing so many. The state of Iowa said, ‘They’re threatened and we need to protect them.’ So they chose to protect them in the primary counties where they are found, which is basically along the Mississippi River and a stretch west over to Winterset. The exception is you can kill one if it’s within 50 yards or 150 feet of an occupied house,” Walters shared.

 

Timber rattlesnakes are large, heavy bodied snakes identifiable by their black chevron markings with a white outline and typically bright, golden body. However, they are darker and more grayish in color when preparing to shed, which can be up to three times in a good year.

 

“That’s when they are most irritable,” Walters warned. “It’s like us when we have a burn. The skin no longer fits and they have to get it off to grow.”

 

Timber rattlers get a new segment of rattles each time they shed their skin, which Walters said dispels the myth that the number of rattles can tell the age of a snake.

 

“They don’t get a rattle per year, but as they grow,” he noted. “Rattles are made of keratin, and they can break off just like you’d break a fingernail.”

 

To protect the rattles, snakes will hold their jet black colored tails in the air. Non-venomous snakes, on the other hand, will drag theirs on the ground.

 

Other timber rattler identifiers include elliptical eyes and heat sensitive pits, a triangular shaped head and narrow neck, as well as a forked tongue. 

 

“The tongue on a snake is very unique. It comes out and picks up molecules off the air, and it takes those molecules back to what’s called a Jacobson’s organ in the top of their mouth and deposits them. The snake can tell things like prey,” Walters shared. “They also use the tongue for direction.”

 

The timber rattlesnake has a set of fangs that operate independently, meaning they can control both or one. Pulling their fangs doesn’t do any good for protection. 

 

“Underneath that skin is four sets of fangs ready to go. Within 24 hours, that snake draws a new fang,” Walters said.

 

The snake’s primary food source is small mammals, but it can only strike half its distance. A six-foot-long snake, for example, could hit three feet. 

 

“They open their mouth to 180 degrees, exposing their fangs, and they reach out and hit their prey. They inject venom into the prey and wait for it to die,” Walters described. “They can eat something up to three times their diameter, and they eat their prey whole. When they are done, a snake has to re-set its jaw to eat again. They will do a yawn, and it snaps back into place and they are ready to go.”

 

Walters said snake venom is two-fold in that it immobilizes prey and also assists in digestion by breaking down tissue and blood vessels—literally rotting the prey from the inside out. 

 

It takes the snakes 28 days to recycle their venom, so they actually control and conserve it carefully. When someone gets too close, a timber rattlesnake will often deliver a warning thump first.

 

“That’s why a majority of bites in the wild are often dry bites, because they need that venom for food,” said Walters.

 

Rattlesnake venom is hemotoxic, affecting the blood vessels and muscle tissue. Although bites occur, they are rarely fatal. According to Walters, there have been 36 fatal rattlesnake bites in Iowa, but no deaths since 1918.

 

These days, victims are given anti-venom, often from horse serum.

 

“The problem with that is, if I get bit and they give me anti-venom, I’ll probably develop an allergic reaction to that horse serum, so I can never have anti-venom again. The latest is sheep, and we’re not getting the allergic reaction,” Walters explained.

 

Most smaller hospitals, especially in this area, don’t carry anti-venom because it expires and is expensive. The facility in Prairie du Chien, Wis., is an exception, said Walters, because he was keeping snakes at his home in McGregor.

 

Joe Brooks, who organized the presentation and was a pharmacist there, saw it firsthand.

 

“From a hospital standpoint, most have like four vials on hand, and that’s just to get started. So they have to transport people to larger facilities because no one has enough anti-venom to really treat someone,” Brooks said. “At Crossing Rivers, we’d get calls all the time. None of ours expired because we were always shipping it somewhere else.”

 

Currently, snake venom is being used in medical research related to heart disease, arthritis, anti-coagulants and even cancer, Walters remarked. 

 

He stressed it’s just one reason to protect the species, whose population has been in decline due to several factors.

 

One of the biggest threats is urban sprawl and loss of habitat. Timber rattlesnakes favor southwest limestone outcrops on goat prairies for den sites so they can bask in the sunlight.

 

“Now, we don’t use fire as much, and goat prairies have become overgrown,” Walters said. “And I can’t tell you how many times I’ve had someone build a house next to a den site.” 

 

Snakes need the fissures and crevices they use as dens to extend below the frost line for brumation, a condition where they go below the frost line and literally stop moving. They will lay lethargic to conserve their energy and body temperature, only emerging when the ground reaches 50 degrees. 

 

Snakes—especially males—will travel up to two miles from the den site. Females travel too, but will stick close when they are gravid, or pregnant. 

 

“They’re very much dependent on where they were born. Timber rattlesnakes religiously go back to the same den site,” Walters explained. 

 

Another threat to the timber rattlesnake population is reproduction—or lack of it. Males live to be about 30 years old but aren’t mature until age five to seven. For females, it takes seven to 11 years to mature and have little ones. Even then, she will only reproduce every three years due to the area’s climate. Winter can be too stressful.

 

“They mate in July or August, and she takes the sample she gets and saves it, and goes through winter. If it’s a good winter and she survives, she’ll have little ones. If it’s a bad winter, she absorbs the sample into her body. The following year is when she becomes gravid and stays around the den site,” Walters said. “They are ovoviviparous, which means their eggs are internal, almost like a human with their babies. When they have little ones, it’s live birth. They come out as neonates in a little, clear sac, then the sac breaks and they come out. They’re alive and ready to go. They are about 10 to 12 inches in length when they are born.”

 

Each female will have about eight to 12 young and stay with them for five days. In that time, the babies imprint on the den site and shed for the first time. Not all will survive, however.

 

“If she had a dozen, and two to three may survive, and then she only gets up to 25 years of age, that’s not many little ones she has to repopulate with,” explained Walters.

 

He also listed accidental vehicle kills, pesticides and an increase in predators like raptors among snake threats. Poachers and collectors, along with the pet trade, have an impact too.

 

Human fear is another.

 

“Everyone kills them as soon as they see them. There’s lack of knowledge and understanding,” Walters said. That’s why educational programs like the one in McGregor are important, he stressed.

 

“Leave them alone and give them respect and distance, and you’ll be just fine,” he said.

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