However lifespan is greatly reduced in the wild.

Captive animals do not have to cope with huger, predators, flash flooding, autos, man, drought or disease.

Wild garters breed in such mass numbers to ensure that the species will survive with high mortality rates.

The more urban the surroundings, the more likely Man will be the biggest influence on lifespan be it intentionally or unintentionally.

To "replace" one garter snake in the wild population takes 2 years, sadly a good number never see maturity to reproduce.

Here in New York State, it is illegal to capture, kill or otherwise molest a rattlesnake, That species take 10 years to replace. (based on data from an animal planet special, feel free to correct if misinformed)

So the captive animals in properly maintained collections are very lucky snakes!!!