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Brood sizes for Thamnophis radix show much geographical variation (Fitch 1985. Misc. Publ. Univ. Kansas Mus. Nat. Hist. 76:l- 76). While brood sizes can range up to 60 (Fitch, up. cit.; Collins 1993. Amphibians and Reptiles in Kansas. Univ. Kansas Mus. Nat. Hist., Lawerence, Kansas, 397 pp.), the brood sizes reported for Colorado have fallen far short of this. Hammerson (1999. Amphibians and Reptiles in Colorado, Second Edition. University Press of Colorado, Niwot, Colorado, 480 pp.) observed brood sizes in Colorado of 16-21 (N = 9), with a mean of 16. Rossman et al. (1996. The Garter Snakes: Evolution and Ecology. University of Oklahoma Press, Norman) reported a range of 5-20 (N = 8) for Colorado, and a brood of 20 was recorded by Ellis and Henderson (1913. Univ. Colorado Studies 1029-129). Other records include brood sizes of 7, 9, 14, 20, and 21 (Hammerson, op. cit.).