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A Story of Survival

Biologists are trying to learn more about the massasauga rattlesnake in the species' last stronghold — Missouri
Friday, October 17, 2003 | 12:00 a.m. CDT; updated 11:56 a.m. CDT, Sunday, July 20, 2008

At the edge of a 30-acre field at Swan Lake National Refuge stands “The Tree of Death.” The tree, named by refuge wildlife biologist Heather Lambert-Doherty, was home to a red-tailed hawk when the researcher first began using state-of-the-art tracking devices to study the venomous and endangered massasauga rattlesnake in this refuge in Sumner.

The Tree of Death earned its moniker after Doherty discovered the tracking device of an unlucky snake named Mr. Bitey dangling from the tree. It was all that remained of Mr. Bitey after his run-in with the red-tailed hawk.

Two years ago, Doherty launched a study of the massasauga snake, a small gray snake identifiable by its brown spots, its dark belly and a small rattle on its tail. The snakes make their home on floodplains and are found in only three parts of Missouri: Squaw Creek National Refuge, Swan Lake National Refuge and Pershing State Park near Swan Lake.

The high-tech method Doherty used in this study is called telemetry. It involves capturing a snake and transporting it to a St. Louis hospital. Once inside the hospital, the snake is hooked up to a heart-rate monitor and put under anesthesia while a radio transmitter is implanted in its body.

Each transmitter installed has a unique frequency, enabling Doherty to find and identify individual snakes.

“They are a beautiful snake,” Doherty said. “They are very docile.”

The massasauga is also an endangered species in Missouri and is a candidate for a federal listing. Massasauga populations have dwindled in recent years, and it is estimated there are only a few thousand left in the country, Doherty said. Many of those snakes are in this state.

“Missouri is the last stronghold for the species,” she said.

The fact that red-tailed hawks are one of the massasauga’s predators is one of the many things Doherty has learned during her seven years of studying the snake. Such findings have helped her develop management plans that are designed to ensure the snake’s survival.

After learning the predators were eating a large number of snakes, Doherty took action. To increase the snakes’ survival rate and raise population numbers, the Swan Lake refuge cut down the trees lining one of the fields in which the snakes hibernate. Without the trees, the hawks could not nest in the area.

Using telemetry is expensive — each device costs about $300 — so Doherty hasn’t been able to use the devices since her first study, which was funded by a grant.

But that doesn’t mean she’s stopped researching the species.

Each year, she tracks the snakes on foot from the time they emerge from hibernation until they retreat back to their burrows in the fall.

When she does catch a snake, she inserts a microchip by hand between the overlapping scales of the snake’s belly. But before she does that, she uses a device to scan the body for a microchip to see if it is a snake she has caught previously.

She records the sex, weight and length of each snake captured. She also takes a blood sample that will later be used for DNA analysis. Biologists are analyzing blood samples from the Swan Lake population and comparing it to the nearby Pershing Park population to see if the two groups once interbred.

Doherty also takes a global-positioning-system reading, which she later plots on a map. This data has revealed that the massasaugas at Swan Lake hibernate on higher ground and migrate to lower ground to forage. This is opposite from what the species does in other areas of the country, she said.

Doherty is still investigating the reasons behind the difference.

However, this past summer didn’t produce many discoveries because Doherty didn’t see many snakes. Because massasauga snakes hibernate in burrows in the ground created by small mammals, the populations are susceptible to flooding, which Swan Lake experienced last spring.

How badly the flood affected populations has yet to be determined.

Doherty said she is planning to apply for a grant to fund another telemetry study next spring that would research how many snakes drowned.

Studying venomous snakes does not come without risk. But over the years, Doherty has perfected her handling techniques. Though handling the venomous snakes can be dangerous, the massasauga is so small that its bite is usually not deadly.

“No one has died from a massasauga rattlesnake bite in the state of Missouri,” she said.

But, she said, if someone does get bitten, he or she should seek medical attention right away.

Doherty said the misconception that snakes are out to attack people is one of the reasons they are threatened. People see a snake, especially a rattlesnake, and immediately kill it, she said.

“You can’t induce a snake to strike unless you are harassing it,” she said. “They use their venom for hunting — they don’t want to use it for defense because they then can’t eat until it is replenished.”

Doherty believes snakes’ bad reputation is the reason why threatened species such as the massasauga don’t get the publicity other animals do. If the massasauga is added to the federal list of endangered species, it will be the first venomous snake to ever be included. Doherty hopes that the snake’s population numbers will never drop so low that the species becomes endangered.

“These snakes are so resilient — if we give them half a chance, they will come back,” she said.

Missouri is also home to two other species of rattlesnakes: the western pygmy rattlesnake and the timber rattlesnake.

Jeff Briggler, a herpetologist with the Missouri Department of Conservation, said that rattlesnakes are found statewide but are rare in the Columbia area.

In fact, Molly Aust, a senior animal control officer in Columbia, said her department has never picked up a rattlesnake in Boone County. Most of the phone calls the department gets are for black or garter snakes, she said.

According to Briggler, people who encounter rattlesnakes typically live in remote areas where snakes lived before homes were built.

People often mistake harmless snakes for rattlesnakes because many species vibrate their tail when alarmed, he said.

Rattlesnakes can be identified by their triangle-shaped head and elliptical eyes. If people do run into a rattlesnake, Briggler advises that they walk around it and leave it alone.

“More people get bit by venomous snakes by trying to kill it,” he said.

If the snake is found in a home, Briggler advises contacting Columbia/Boone County Animal Control or a conservation agent.

Aust said Animal Control will only pick up snakes if they are inside a home or if they are in an area with young children.

If a person does spot a snake and calls Animal Control, Aust said they should make sure someone keeps an eye on the snake so it doesn’t slither away while the call is being made.


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