Movements Made by Two Species of Pocket Gophers

Abstract

Information is presented on dispersal movements made by valley pocket gophers, Thomomys bottae, and northern pocket gophers, T. talpoides, introduced into areas with which the animals were unfamiliar. Most long movements were made under snow cover. Thomomys talpoides dispersed from introduction sites more frequently and moved greater distances than did T. bottae. The mean distance moved by T. talpoides in one year was 785 feet, and the longest movement was 2590 feet. Comparable figures for T. bottae are 198 feet and 900 feet. The differences in dispersal abilities or tendencies between the species are probably basic behavioral distinctions which may be related to the differences in the environments occupied by the animals. Little information is available on movements made by pocket gophers under natural conditions. Bryant (1913), Howell (1922), and Imler (1945) reported on surface movements of pocket gophers, and Howard and Childs (1959) recorded distances 14 prebreeding individuals traveled. In the present study, distances moved by transplanted individuals of two closely related species of pocket gophers were recorded. On the basis of these records, the abilities or tendencies of the animals to disperse are compared and discussed. The study area was approximately six miles north of Cotopaxi, Fremont Co., Colorado, at roughly 7500 feet elevation. The locality is mountainous and rocky, and is characterized by pinyon pine, Pinus edulis, juniper, Juniperus scopulorum, ponderosa pine, Pinus ponderosa, Gambel oak, Quercus gambellii, and mountain mahogany, Cercocarpus montanus. The ground cover of the areas occupied by pocket gophers is dominated by blue grama, Bouteloua gracilis, and sleepygrass, Stipa robusta. Other conspicuous plants are rabbitbrush, Chrysothamnus nauseosus, summer-cypress, Kochia scoparia, and western beeplant, Cleome serrulata. Acknowledgments.-Thisstudy was supported by National Science Foundation Grant G-9807. I would like to express my appreciation for critically reading the manuscript to Paul H. Baldwin, Department of Zoology, Colorado State University; Richard M. Hansen, Colorado State University, Agricultural Experiment Station; and Ronald A. Ryder, Department of Forest Recreation and Wildlife Management, Colorado State University. For assistance with field work I wish to thank Roger E. Baker, Keith E. Evans, LeMoyne B. Marlatt, Gary T. Myers, and Ronald L. Perry.