Sunday, October 24, 2010

Massasauga Envenomations and Conservation

Conservation of venomous snakes can be a hard sell to a public that is fearful and despises snakes. The rattlesnake genus Sistrurus contains two species, one of which, the Massasauga (S. catenatus), is considered endangered over much of its distribution in the eastern North America. The Massasauga is perhaps the most studied snake on the planet and journals are filled with numerous recommendations for its conservation which range from road signs alerting motorists to its presence and under pavement tunnels, to altering footpaths through parks and collecting the last remaining specimens from a population for captive breeding. Legislation to protect such species is an effort but rarely does it change people's behavior. In many places Massasaugas are found near human habitations, usually because developers built the houses in snake habitat, such as drained wetlands, floodplains, or savannas with existing populations of snakes. In these areas humans tend to be a major source of snake mortality. Even though snake populations in these suburban areas tend to be low snakes are often killed by traffic or fearful humans and collected for the pet trade. Gravid females are often the most obvious snakes in the population because they tend to thermoregulate more frequently to maintain optimal temperatures for their embryos. This morning (Sunday, October 24, 2010) the Chicago Tribune is carrying an AP story that suggests Massasauga envenomations are increasing in Lower Michigan. Rattlesnake bites which are usually rare have apparently increased (nobody is keeping track of the numbers), but bites have been reported in: Orion Township, Highland Recreation Area, and Flushing; Spring Harbor Township. Additionally Poison Control at Children's Hospital of Michigan reports at least four bites this year. The increased number of envenomations is being attributed to warmer weather that has lasted into the autumn. It seems likely that the snakes have not only remained active longer, but that people may be spending more time outdoors. This is not good news for the efforts to conserve the snake. It is somewhat ironic that the very first attempt to make an animal resistant to snake venom was done by Henry Sewall, working at the University of Michigan in 1886–1887. Sewall used Pigeons and venom from the Eastern Massasauga (Sistrusus c. catenatus) also known as the "swamp rattler" to demonstrate that organisms could be made resistant to venom. Sewall injected small doses that were gradually increased until the birds could withstand 10 times the lethal dosage. These experiments were the stimulus for developing other antitoxins, not only for snakebites, but for other diseases that resulted from bacterial toxins like diphtheria.

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