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Migration of Timber Rattlesnakes

The timber rattlesnake, critically endangered, once inhabited the entire East Coast and Midwest, and southeastern Canada. It's now confined to a few locations from New England south through the Appalachian Mountains. Timber rattlesnakes spend their winters hibernating in communal dens. In the spring, those not pregnant migrate to feeding and breeding ranges.

Crotalus Horridus

The number of timber rattlesnake subspecies is an area of contention. Herpetologists and zoologists count one to three, but only one is officially recognized beyond a doubt. Crotalus horrridus or Crotalus horridus horridus is the official species. Crotalus horridus atricaudatus is the proposed subspecies for the southeastern coastal plain canebrake rattlesnake population of timber rattlesnakes, and a as-yet-unnamed western subspecies is also proposed by some researchers. Timber rattlesnakes are essentially harmless to humans. They feed primarily on rodents and other small mammals and use their buzzing rattle to warn predators away. They try to avoid confrontation, biting only when provoked.


Timber rattlesnakes' lives revolve around hibernation and reproduction. They can live for more than 20 years. Females bear young once every two to four years. Females become reproductively mature around age 7 but in cases as late as age 10. A female timber rattler typically bears only three to four litters of baby snakes in her lifetime.

The Migration

Timber rattlers spend their winters hibernating in multiple-species dens. The same dens serve for generations. Pregnant females stay near their winter dens in spring while males, females who aren't pregnant travel to find food and mates. They migrate up to five miles to their summer ranges, then return when winter rolls around again. Both trips are extremely treacherous for the snakes. They must stave off starvation, evade predators and navigate human developments. Humans kill these migrating snakes out of fear or malice, or by accident. Once they reach their summer ranges, they travel within them to find prey and mates. Summer range parameters vary by gender and age but can be as large as 160 acres for a single snake.

Migration Disruption and Endangerment

Rattlesnakes are critically endangered in all of their remaining habitat, but they currently lack federal protection. They are purposely poached for the pet trade and commercial sale of their body parts. Their hibernation and migration make them particularly vulnerable. "Rattlesnake roundups" are particularly devastating to the species, as research by the New York Herpetological Society shows most snakes killed in roundups are pregnant -- hunters target the rocky, sunny outcroppings where pregnant snakes spend their summers near their winter dens. Meanwhile, as migrating snakes use the same trails, summer ranges and winter dens year after year, and their young adapt them. Human development fragment these habitats. As human incursion increases, so do the hazards facing snakes.