Timber Rattlesnakes are the only poisonous snake in New Hampshire. They live solitary lives except during the Winter when they will group up for more warmth. Timber Rattlesnakes are carnivores with a life span between 16-22 years. They have a gestation period of 4-5 months producing 4-14 young, most commonly 9 and breed every 3-5 years during August & September. Timber Rattlesnakes can move 2-3mph in short bursts and adults average between 30-60 inches long.