Fish and Wildlife Service has stated that many locations that previously had healthy populations of garter snakes are now in decline due to land development pressure and the filling of wetlands in San Mateo County over the last sixty years.

This subspecies avoids brackish marsh areas because its preferred prey, the California red-legged frog (Rana draytonii), cannot survive in saline water.

[4] The zone between stream and pond habitats and grasslands or bank sides is characteristically utilized for basking, while nearby dense vegetation or water often provide escape cover.

Newborn and juvenile San Francisco garter snakes depend heavily upon Pacific treefrogs (Pseudacris regilla ) as prey.

San Francisco garter snakes are one of the few animals capable of ingesting the toxic California newt (Taricha torosa) without incurring sickness or death.

Accordingly, the subspecies tetrataenia was reaffirmed for the San Francisco garter snake and the races concinnus and infernalis retain their historical definition.

Herpetologist Sean Barry notes that the three subspecies divide up the food resources as follows: While the findings of the ICZN have given the San Francisco garter snake unique taxonomic standing for now, a molecular study challenges the subspecific status of this population.

Janzen [7] analyzed sequences in mitochondrial DNA to determine relationships within the subspecies of the common garter snake (T. sirtalis).

The authors suggest that sequencing nuclear DNA may provide a more precise analytical tool to crack some of the ultimate taxonomic quandaries of the San Francisco garter snake and its relatives.

These environmental elements include loss of habitat from agricultural, commercial and urban development, as well as collection by reptile fanciers and breeders.

[9] In 2023 the San Francisco garter snake was featured on a United States Postal Service Forever stamp as part of the Endangered Species set, based on a photograph from Joel Sartore's Photo Ark.