Found this on Snakes Alive Snakes Alive. Even though they're discussing the red sided garters, I would think that the ratios would be about the same regardless of the species? What do you think?


REPRODUCTIVE CAPACITY

Recruitment for the red-sided garter snake is
extremely slow. They do not breed for at least 3 years and likely breed every
other year after that. First broods are seldom more than 1-5 young.
Approximately 80% of the young do not survive their first winter and 50% of each
year class dies annually thereafter. Adult females (over 80cm.) are vital to the
well-being of all populations. These females produce as many as 40 young each at
least every other year. A snake population cannot increase without a major
component of adult females.