Produced by Chris Curnow, Tom Cosmas, Joseph Cooper and the Online Distributed Proofreading Team at http://www.pgdp.net UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY Volume 10, No. 4, pp. 129-161, 8 figs. in text, 6 tables December 19, 1957 Aspects of Reproduction and Development in the Prairie Vole (Microtus ochrogaster) BY HENRY S. FITCH UNIVERSITY OF KANSAS LAWRENCE 1957 UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Harrison B. Tordoff Volume 10, No. 4, pp. 129-161, 8 figs. in text, 6 tables Published December 19, 1957 UNIVERSITY OF KANSAS Lawrence, Kansas PRINTED IN THE STATE PRINTING PLANT TOPEKA, KANSAS 1957 [Illustration: Look for the Union label!] 26-7561 Aspects of Reproduction and Development in the Prairie Vole (Microtus ochrogaster) BY HENRY S. FITCH INTRODUCTION The prairie vole is by far the most abundant mammal on the University of Kansas Natural History Reservation and on grassland areas throughout northeastern Kansas. This vole therefore affects the vegetation, perhaps more than any other native vertebrate, and it is an important food source for most of the vertebrate predators. Since the Reservation was established, in 1948, more data have been accumulated concerning this vole than for any other species of animal there. From February, 1950, to February, 1954, a grid of live-traps at 50-foot intervals was set for several days each month in a three-acre field inhabited by voles, and the population of marked individuals was studied throughout the four-year period. From November, 1953, to June, 1956, a half-acre trap grid with 20-foot interval was used on an area adjoining the three-acre field. Other trap lines in somewhat different habitats were maintained for shorter periods as a basis for comparison. By June, 1956, a total of some 3550 voles had been caught and recorded 14,750 times in all. The present report is a preliminary attempt to analyze, in part, these extensive data, and is concerned with certain phases of the species' reproduction and growth that have bearing on the observed population changes from month to month and from year to year on the Reservation. Through the studies of Jameson (1947) and Martin (1956), both made in the same general area as my own, and several earlier studies, the life history and ecology of the prairie vole are already well known. The present report, with much larger amounts of data, further clarifies certain phases of the ecology; and by using types of data not available to Jameson and Martin I have dealt with some topics not included in their reports.