What core issue, combined with habitat loss, drives the endangered classification of this subspecies?

Lack of plasticity or adaptability compared to other garter snakes

The severe conservation status of the San Francisco garter snake is attributed to a combination of factors that undermine its ability to persist in the rapidly changing environment of the Bay Area. While extensive habitat loss due to development is a primary threat, the snake's inherent biological characteristics exacerbate the problem. Unlike many other garter snake subspecies across North America that demonstrate high plasticity, the San Francisco garter snake has failed to show the same ability to adapt its requirements or range to accommodate suburban or agricultural changes. This inherent lack of adaptability means its survival remains intrinsically tied to specific, often undisturbed, coastal ecosystems, making any loss of those unique areas exponentially more damaging to the overall population stability.