Population Structure and Biomass of Some Common Snakes in Central North America

Abstract

Samples of 113 to 1762 individuals were obtained from local populations of 11 common species of snakes in Kansas and one in Oklahoma. An age-size correlation was established for each species from the records of marked individuals that were recaptured. Each snake in the samples was tentatively allocated on the basis of its snout-vent length (or alternatively on its rattle string in Crotalus). Local populations were interpreted to consist of from eight (Thamnophis sirtalis) to 18 (Crotalus atrox) annual age cohorts. In samples of Coluber constrictor, Nerodia sipedon, and Thamnophis sirtalis, females outnumbered males and attained larger mean size. In Nerodia and Thamnophis, females survived longer than males; in Coluber the sexes were similar in longevity. In Agkistrodon contortrix, Crotalus atrox, C. horridus, C. viridis, Elaphe obsoleta, Lampropeltis calligaster, L. triangulum, and Pituophis catenifer, males outnumbered females, grew larger,-and survived longer on average. In Diadophis punctatus, males were more numerous than females and survived longer, but females had average larger size. In each species sample, first-year young were poorly represented, with only 4 to 46% of expected numbers, and it seemed that their cryptic behavior and markings caused them to be overlooked much more often than adults, regardless of the method of sampling. Biomasss calculations indicated that Diadophis punctatus constituted nearly half of the total, with Coluber constrictor, Elaphe obsoleta, Thamnophis sirtalis, Lampropeltis calligaster, and Agkistrodon contortrix making up from 18% to 5%, whereas Crotalus horriidus, Lampropeltis triangulum, Nerodia sipedon, and Pituophis catenifer made up only very small percentages