Produced by Chris Curnow, Joseph Cooper, Erica Pfister-Altschul and the Online Distributed Proofreading Team at https://www.pgdp.net UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY Volume 9, No. 12, pp 363-384, 7 figs, in text, 1 table February 21, 1958 Geographic Variation in the Pocket Gopher, Thomomys bottae, in Colorado BY PHILLIP M. YOUNGMAN UNIVERSITY OF KANSAS LAWRENCE 1958 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Robert W. Wilson Volume 9, No. 12, pp. 363-384, 7 figs. in text, 1 table Published February 21, 1958 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED IN THE STATE PRINTING PLANT TOPEKA, KANSAS 1958 Geographic Variation in the Pocket Gopher, Thomomys bottae, in Colorado BY PHILLIP M. YOUNGMAN INTRODUCTION Two species of pocket gophers of the genus _Thomomys_ (Family Geomyidae) occur in Colorado, _Thomomys bottae_ (see fig. 1) in the low valleys in the south-central and southwestern parts of the state and _Thomomys talpoides_ mainly in the mountains and high valleys. _Thomomys bottae_ occurs primarily in the Piñon-juniper, Ponderosa Pine, and Short Grass zones of Daubenmire (1943) but in some localities is found in the Douglas Fir Zone. _Thomomys talpoides_ occupies primarily the Douglas Fir Zone and Engelmann Spruce-Subalpine Spruce Zone but is found also in the Piñon-juniper and Short Grass zones in some localities. The ranges of the two species do not overlap in the strict sense but interdigitate in a parapatric type of distribution. Two other pocket gophers, _Geomys bursarius_ and _Cratogeomys castanops_, also occur in Colorado--in the Upper Sonoran Life-Zone. _Geomys bursarius_ occupies much of the Great Plains, whereas _Cratogeomys castanops_ is found only on the plains in the southeastern part of the state. The objectives of the study, reported on here, were to learn the geographic distribution of _Thomomys bottae_ in Colorado, to find means for recognizing the different subspecies, and to describe individual and geographic variation. I am indebted to Mr. Sydney Anderson and Professor E. Raymond Hall for many helpful suggestions and for their critical reading of the manuscript, to Dr. Richard S. Miller, who made the collection of many of the specimens possible, and to Dr. Richard M. Hansen for numerous suggestions. I wish to express my appreciation also to the following for the loan of specimens in their care: Alfred M. Bailey and A. A. Rogers, Colorado Museum of Natural History, Denver, Colorado; David H. Johnson, United States National Museum, Washington, D. C; Robert W. Lechleitner, Colorado State University, Fort Collins, Colorado; and Robert Z. Brown, Colorado College, Colorado Springs, Colorado. METHODS