1. Deep pit between nostril and eye; rattle on tail tip .....Western Rattlesnake, Crotalus oreganus
  2. No deep pit or rattle .....2


  1. No enlarged chin shields; blunt tail .....Northern Rubber Boa, Charina bottae
  2. Two pairs of enlarged chin shields; tail long and pointed (unless broken off) .....3


  1. Some or all dorsal scales keeled .....4
  2. All dorsal scales smooth .....7


  1. Four prefrontals; body with large blotches .....Gophersnake, Pituophis catenifer
  2. Two prefrontals; body striped or with small spots .....5


  1. Eight upper labials; conspicuous checkered pattern .....Terrestrial Gartersnake, Thamnophis elegans
  2. Seven upper labials; never with conspicuous checkered pattern, although sometimes with dots .....6


  1. 17 scale rows at midbody; usually a dark postocular stripe contrasting with paler head color; pattern very variable (dorsal stripe may be lacking, ground color may be pale) .....Northwestern Gartersnake, Thamnophis ordinoides
  2. 19 scale rows at midbody; head usually all dark above; always dark with light stripes above .....Common Gartersnake, Thamnophis sirtalis


  1. Anal plate entire; body brightly banded .....California Mountain Kingsnake, Lampropeltis zonata
  2. Anal plate divided; not brightly banded .....8


  1. Spine on tip of tail; belly finely barred with black .....Common Sharp-tailed Snake, Contia tenuis
  2. No spine on tail tip; belly colored otherwise .....9


  1. Orange belly and ring around neck .....Ring-necked Snake, Diadophis punctatus
  2. No neck ring; belly colored otherwise .....10


  1. Pupil vertical; spotted above, with large blotches on neck .....Desert Night Snake, Hypsiglena chlorophaea
  2. Pupil round; unicolor, striped or spotted, no large blotches on neck .....11


  1. Finely striped above Striped Whipsnake, Coluber taeniatus
  2. Unicolor (adults) or finely spotted or banded above (young) .....North American Racer, Coluber constrictor

Adapted by Dennis Paulson from key in Nussbaum, R. A., E. D. Brodie, Jr., and R. M. Storm. 1983. Amphibians & Reptiles of the Pacific Northwest. Univ. Press of Idaho, Moscow. Names revised December 2013.