Geographic and Non-Geographic Variation in Microtus Pennsylvanicus in Nebraska and Kansas

A total of 275 specimens of the meadow vole were collected in six locations in Nebraska and Kansas. Standard skin measurements and 21 skull measurements were taken and treated statistically \u27with the aid of an IBM 1620 computer. Mean, range, standard error, and coefficient of variability were calculated on each variable. The specially designed program all owed selecting for age, sex, locality and date on all the data. The aging technique utilizing three features on the back or the cranium proved unsuccessful as it was found to vary significantly with age and geography. Individual variation discovered here was found to essentially substantiate works of previous authors but encompasses a greater variety of features. Sexual dimorphism is found significant at varying levels, ranging from less than .750 to .990. Geographic variation is found to be very high owing to the ecological requirements and ultimately the distributional pattern of the species. The significance found here appears to result, to a large degree, from distances between the populations. A cline in characters was uncovered in both measurements and pelage. Animals to the South and West are generally larger and darker than those North and East. The status of M.p. finitus is reviewed with respect to the high level of individual and geographic variation seemingly intrinsic to these marginal populations. The population representing M.p. finitus from Dundy County, Nebraska, is no more distinct than any other populations studied and should be referred to the race Pennsylvanicus