A REGIONAL COMPARISON OF COTTONTAIL RABBIT REPRODUCTION IN OHIO DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By NORMAN CURTISS NEGUS, B* A., M. A. s}:s);:$:s}5sfe The Ohio State University 1956 Approved by: " "<F Adviser Department of Zoology and Entomology TABLE OF CONTENTS Chapter- I - INTRODUCTION. • .......................... 1 Chapter- II - MATERIALS AND METHODS, .......... ...9 Chapter III - R E S U L T S . ..... ... • ............... .53 : Chapter- IV - DISCUSSION...... ...................127 Chapter- V - SUMMARY AND CONCLUSIONS..,...............!1^ - Chapter VI - RECOMMENDAT IONS .... ... iMf APPENDIX.... ............ ...... ...................l1^ LITERATURE: CITED.....................................l1^ AUTOBIOGRAPHY........................................152 ii LIST OF ILLUSTRATIONS Figur© 1. Map of physiographic regions of Ohio....*. **.13 Figure 2# Map of general soil regions of Ohio........ ..I1* Figure 3. Map of collecting localities............ .,,,19 Figure *f. Nestling fur:;. ......... ......25 Figure 5* Juvenal pelage-'. .... ....26 Figure 6 . Subadult pelage.... 27 Figure- 7. Adult summer pelage. .... ......28 Figure 8 , X-ray photograph of forelegs of adult and ' juvenile: Cottontail rabbits.......... ... .32 Figure 9* Relationship of crown-rump length to age in New Zealand Whit© rabbit embryos......36 Figure 10. Relationship of ear pinna length to age in New Zealand White rabbit embryos......37 Figure: 11. A V-day embryo of New Zealand White rabbit..39 Figure: 12?. A 17-day embryo of New Zealand White rabbit. .........*••••39 Figure: 13. A 20-day embryo of New Zealand White rabbit. ..•••..... •»••......•••••••••••••39 Figure l1*. A 21+~day fetusoof New Zealand' White rabbit........ .............. .......... Figure 15. A 28-day fetus of New Zealand White rabbit..*,. ............. *+0 Figure 16. A 30-day fetus of New Zealand White rabbit.............. kO Figure 17. Photomicrograph of maturing Graafian follicles in cottontail rabbit ovary.....k7 iii Figure 18, Photomicrograph of freshly formed corpus: luteum. ..... .................. .b7 * Figure 19* Photomicrograph of active corpus luteum of pregnancy............................*+8 Figure 20. Photomicrograph of active corpus luteum enlarged to show cellular .structure.....*1-8 Figure 21. Photomicrograph of corpus albicantia from a previous pregnancy........... ...^9 Figure 22. Photomicrograph of corpus albicantia at the end of the breeding season..........1+9 Figure 23. Frequency of estimated parturition dates for litters of cottontail rabbits.......81 iv LIST OF TABLES Table 1. Characteristics of Known-Age Embryos from New Zealand White Rabbit Breeding Experiment......... 35 Table 2, Data on Adult Female Cottontail Rabbits from Urbana Game Farm...... 56 Table 3, Unglaciated Allegheny Plateau Data on Subadult Cottontail Rabbits......... 6 6 - 6 9 Table 4. Till Plain Data on Subadult Cottontail Rabbits.............................70-73 Table 5* The Pelage Stages of Female Cottontails Correlated with Reproduction........ 89-90 Table 6 , Data from Breeding Experiment Using New Zealand White Rabbits ..... 93 Table 7 , Frequency Distribution of Litter Sizes of Cottontails from Areas A and B.-..... 96 Table 8 , Summary of Analysis of Variance of Litter Sizes from Areas A and B............... 99 Table 9 , Summary of a Comparison of Mean Litter Sizes from Areas A and B .......... 101 Table 10, Frequency of Regional Litter Sizes of Cottontails ........ 103 Table 11, Analysis of B luegrass Samples for Calcium and Phosphorus Content........ 105 Table 12, Comparison of Calcium and Phosphorus Content in Samples of Bluegrass from Areas A and B ................... 106 v Table 13. Corpora Lutea and Albicantia in Left anddRight Ovaries of Cottontail Rabbits.............................. 108 Tabl6el4. Embryos and Scars in Left and Right Uterine H orns .............. 109 Table 15. Individual Litter Records from Areas A and B.............................. Ill Table 16. Adult Male Weights..................... 119 Table 17. Summary of a Comparison of Mean Weights of Adult Male Cottontails from Areas A and B .............................. 120 Table 18. Testis Length of Adult Ma les 122 Tableel9. Humeri Lengths of Adult Cottontails.... 124 Table 20, Humeri Weights of Adult Cottontails.... 125 vi - 1- Chapter I INTRODUCTION Numerous studies have been conducted on various phases of the ecology of the Mearns cottontail rabbit, Svlvilagus floridanus: mearnsii (J.A. Allen). VJhile there is no doubt that the results of these investigations have contributed much to our knowledge: of the species, there remain many gaps in the known bionomics of the cottontail which is indeed surprising in view of its great economic importance:. Often previous studies have been repetitions of work conducted in some other state or locality. The result has been a large amount of data relative to move­ ments, nesting sites, pre and post-hunting season popula­ tions, and sex ratios, whereas a. paucity of basic informa­ tion exists relative to reproductive physiology and envi­ ronmental factors. The present study was designed to evaluate the repro­ ductive performance of wild cottontail rabbit populations and to compare various reproductive phenomena, in areas of high and low soil fertility. It was the opinion of the in­ vestigator that such an approach might yield basic infor­ mation on cottontail reproduction as well as afford some insight into the factors which"affect population densities in various regions of Ohio. - 2 - The primary objectives of the study were* 1. To study the relative fertility and fecundity of cottontail rabbit populations with respect to good and poor soil types in Ohio* 2, To determine the length of the breeding season and number of litters produced per year in var­ ious regions* 3* To determine the breeding segment of the popula­ tions and the age at which sexual maturity is attained* if* To gain some knowledge of the factors affecting the various reproductive phenomena of the popula­ tions* As is frequently the case in studies which Involve the collection of data through field work, not all of the foregoing objectives were realized to their fullest extent* The writer feels, however, that a number of important con­ tributions to our knowledge of cottontail ecology have re­ sulted from this study* This study was begun in the summer of 1952 and was continued into the spring of 1955* Financial support was gained from the Ohio Cooperative Wildlife Research Unit* The Unit is supported jointly by the U.S. fish and Wildlife - 3 - Service, the Ohio Division of Wildlife, the Ohio State Uni­ versity, and the Wildlife Management Institute* In addition, a supplementary research grant was contributed by the Wild­ life Management Institute In 1953* The accumulation of data for a project of this magni­ tude would not have been possible were it not for the co­ operation of many individuals* Many of the personnel of the Ohio Division of Wildlife contributed generously of their time or facilities* In particular the writer wishes to acknowledge the assistance of Mr* E*B* Nash, Mr* Karl E* Bednarik, Mr* C.E. Khoder, Mr* James 0* Lee, the late Mr* PTank D* Bailer, Mr* Bodney J. Smith, Mr* William B* Edwards, Mr* Paul J* Moore, Dr* Ployd B* Chapman, Dr* Charles A* Dambach and Mr* William B« Bender shot* Contri­ butions, suggestions, advice and assistance by various per­ sonnel from the Ohio Cooperative Wildlife Besearch Unit have been of inestimable value in the completion of this research* Those deserving particular mention for the great amount of time so generously contributed in the collection of specimens and other tasks are Mr* Bobert 6* Sagar, Dr* E* H* Dustman, Dr* E*E* Good, Mr* Charles Cr is pens, Jr*, Mr* Bobert W* Winner, Mr* Paul A* Stewart, and Mr* Francis w* Kessler* In particular the writer wishes to acknowledge the patience, guidance and encouragement afforded him through- - If - out the study by his adviser, Dr# E.H. Dustman# Mr# John McCready rendered valuable advice in regard to the X-ray of specimens and use of the X-ray camera purchased by the Research Unit# Dr, Maurice L# Giltz assisted in the devel­ opment of the staining and sectioning technique used in the preparation of ovarian material and in the preparation of a large amount of the ovarian material examined during the study# Dr# Vincent W. Schultz rendered valuable advice and assistance in regard to statistical analysis of the data# The -writers wife assisted greatly in many phases of the preparation of the manuscript. Previous Work on the Cottontail and Other Species Reproductive behavior of cottontail rabbits has been studied more or less extensively in New York, Michigan, Pennsylvania, Kentucky, Virginia, Missouri and Connecticut# In the northern states there is general agreement from the results of investigations made by Trippensee (1936), Haugen (19^2), Beule (19^6), and Smith (1950) that the breeding season of cottontails may extend over a ^-0-week period from January to September# In Virginia, however, Lewellyn and Handley (19^5) report that breeding starts early in March with some exceptions# It is likewise generally considered by Beule (19^1), Haugen (191+2), Cooley (19^6), and Smith (1990) that cottontails do not breed during their first - 5 _ summer. In Pennsylvania, Beule found no indication of breed­ ing during the first year* Dalke et al (19^2) in an exten­ sive investigation of cottontails in Connecticut,