They may also feed on juvenile bullfrogs ( Rana catesbeiana ) .
They are unable to consume adults ; in fact , adult bullfrogs prey on juvenile garter snakes , and may be a contributing factor in the population decline of the San Francisco garter snake .
They may also feed on juvenile bullfrogs ( Rana catesbeiana ) , but they are unable to consume adults ; in fact , adult bullfrogs prey on juvenile garter snakes , and may be a contributing factor in the population decline of the San Francisco garter snake .