San Francisco Garter Snake - Taxonomy and Relation To Other Garter Snakes

Taxonomy and Relation To Other Garter Snakes

For a brief period from 1996 to 2000 there was confusion over the differentiation of the San Francisco garter snake from two other subspecies, known as the California red-sided garter snake (T. s. infernalis) and the Oregon red-spotted garter snake (T. s. concinnus). Barry petitioned the International Commission on Zoological Nomenclature (ICZN) to suppress the changes proposed in 1996 to merge two of these species. In 2000, the ICZN agreed and voted to retain the historical taxonomic arrangement of subspecies within this evolutionary lineage. Accordingly, the subspecies tetrataenia was reaffirmed for the San Francisco garter snake and the races concinnus and infernalis retain their historical definition.

The San Francisco garter snake cohabits ecosystems that host two other species of garter snake: the coast garter snake (Thamnophis elegans terrestris), a subspecies of Western Terrestrial Garter Snake (T. elegans), and the Santa Cruz aquatic garter snake (Thamnophis atratus atratus) a subspecies of the aquatic garter snake (T. atratus). These three subspecies are known to prey upon same foods; however, their preferences are slightly different. Herpetologist Sean Barry notes that they divide up the food resource as follows:

• The San Francisco garter snake eats primarily small frogs;
• The coast garter snake eats principally slugs, and
• The Santa Cruz aquatic garter snake eats preferentially minute fish and amphibian larvae.