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Michigan Remains Last Stronghold for Eastern Massasauga Rattlesnake

August 18, 2005

The eastern massasauga rattlesnake, Michigan's only venomous snake, is a rare sight for most state residents. In fact, according to Yu Man Lee, associate zoologist for the Michigan Natural Features Inventory, Michigan may well be the last U.S. stronghold for this species.

Eastern massasauga rattlesnakeHistorically, the eastern massasauga has been found in a variety of wetlands and adjacent uplands throughout the Lower Peninsula. According to a 1994-1996 status assessment conducted by MNFI, the eastern massasauga has been documented at 204 sites in 50 counties in Michigan.

Most of the sightings have been reported in Oakland, Livingston, Jackson and Washtenaw counties in southeast Michigan and in Allegan, Barry and Kalamazoo counties in southwest Michigan. The massasauga also appears to be concentrated in Iosco, Crawford and Kalkaska counties in northern Michigan.

"Although massasaugas still can be found at a number of sites, their absence from sites where they had been previously documented or reported indicates this species is declining in many parts of its former range," Lee said.

The main reasons for the decline, she said, are the loss of wetland habitat and harassment by humans.

"Like most snakes, it will avoid confrontation with humans," Lee said. "The massasauga is not prone to strike -- preferring to leave the area when it is threatened. But like any animal, these snakes will protect themselves when they sense anything that is a potential predator or threat. It is best to treat them with respect and leave them alone."

two people capture a snakeThe eastern massasauga currently is listed as a species of special concern by the Michigan Department of Natural Resources, and is listed as a candidate species under the Federal Endangered Species Act. As part of efforts to conserve this species, the U.S. Fish and Wildlife Service has initiated a multi-state survey to establish the current range and status of the massasauga, and is working with those states to protect this species through Candidate Conservation Agreements.

To ensure the long-term survival of the eastern massasauga in Michigan, it is important to understand the species' current status and distribution, the critical habitats needed for its survival, the threats facing this species and how to effectively address and minimize those threats.

Field surveys to identify massasauga populations and habitat throughout the Lower Peninsula were conducted from 2001-2004. To date, these surveys and reports from the general public have documented massasaugas at more than 79 sites in 27 counties.

Researchers also have conducted several radio-telemetry studies to examine massasauga ecology, behavior and habitat use in Michigan.

Eastern massasauga rattlesnakeOne of those studies is taking place at Seven Lakes State Park in suburban Oakland County in southeast Michigan.

In 2002 DNR wildlife staff began surveying the park for the massasauga. Reports from park employees indicated these snakes were seen (and killed) crossing the roads in the park.

"Although only small pockets of snake habitat remain in the park, our one-month survey located three snakes in different areas of the park," said Julie Oakes, DNR wildlife habitat biologist. "One snake was captured in early October."

Biologists attempted to track it by bathing the snake in a fluorescent powder. A handheld battery-powered black light was used to follow the snake's trail at night. The snake was tracked for three nights, before the powder had become too faint to follow.

"The study prompted us secure funding from the Nongame Wildlife Fund for more effective radio telemetry work the following spring," Oakes said.

transmitter implanted in snakeIn spring 2003, Dr. Bruce Kingsbury, director of the Center for Reptile and Amphibian Conservation and Management at Indiana-Purdue University Fort Wayne, was contacted to surgically implant transmitters into three captured snakes, so the reptiles could be tracked using radio telemetry.

GPS locations were taken on the snakes as well as data recorded on temperature, time of day, habitat, activity of snake, etc. Other snakes observed during tracking, which did not have a transmitter in them, were identified by a GPS location and marked as an element occurrence.

The snakes were tracked until fall when they entered their hibernaculums (hibernating locations). A home range could be determined for only one snake that was tracked all summer. Its home range, about 2.2 acres in size, was located next to a busy boat launch area.

sample taken from snakeIn 2004, eight more transmitters were implanted in snakes at Seven Lakes. These were tracked along with two snakes from 2003 that still had working transmitters. Oakes said biologists have been tracking 13 active snakes at Seven Lakes this year.

"This radio-telemetry study is providing valuable information on the movements and habitat preferences of snakes," Oakes said. "The project also has received good media coverage, which has prompted calls from local citizens on how to safely 'move' a snake off their porch or out of their yard. This shows we can change public attitudes about snakes through education, and that people can learn to coexist with venomous snakes."

The DNR encourages the public to report any massasauga sightings and has a report form on its Web site at To assist with verification, the observer should include a color photo of the observed snake. Do not pick the snake up or kill it.

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