Newborn San Francisco garter snakes (Thamnophis sirtalis tetrataenia) exhibit a highly directed feeding response towards small frogs and selected salamander species. However, their response to other common garter snake food items such as worms, slugs, and small fishes is minimal, and feeding skills for these items must be acquired through trial and error learning. In a similar manner, hatchling Alameda whipsnakes (Mastacophis lateralis euryxanthus) exhibit an immediate feeding orientation toward small lizards. Other potential food items in their habitat such as grasshoppers, newborn mice, and young frogs consistently elicit no direct feeding response. Such innate feeding responses may accrue to these species a distinct competitive advantage for their young when their preferred prey species are abundant. However, in times of preferred prey scarcity, the lack of a more universal feeding response may be a disadvantage in the face of competition with the young of other snake species. This in turn may account for the general scarcity of such endangered and threatened reptiles with highly specialized feeding habits.
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