Ecology of Bighorn Sheep of Wildhorse Island Flathead Lake Montana
Total Page：16
File Type：pdf, Size：1020Kb
University of Montana ScholarWorks at University of Montana Graduate Student Theses, Dissertations, & Professional Papers Graduate School 1973 Ecology of bighorn sheep of Wildhorse Island Flathead Lake Montana John Wayne Matthews The University of Montana Follow this and additional works at: https://scholarworks.umt.edu/etd Let us know how access to this document benefits ou.y Recommended Citation Matthews, John Wayne, "Ecology of bighorn sheep of Wildhorse Island Flathead Lake Montana" (1973). Graduate Student Theses, Dissertations, & Professional Papers. 6499. https://scholarworks.umt.edu/etd/6499 This Thesis is brought to you for free and open access by the Graduate School at ScholarWorks at University of Montana. It has been accepted for inclusion in Graduate Student Theses, Dissertations, & Professional Papers by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact [email protected]. ECOLOGY OF BIGHORN SHEEP ON WILDHORSE ISLAND FLATHEAD LAKE, MONTANA by JOHN W. MATTHEWS B.S., Washington State University at Pullman, 1967 Present in Partial Fulfillment of the Requirements for the Degree of Master of Science UNIVERSITY OF MONTANA 1973 chool l A j J J L j . h UMI Number: EP37300 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. UMT Oiweftatkxi PuWishèng UMI EP37300 Published by ProQuest LLC (2013). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48 1 0 6 - 1346 AC KNOWLEDGEMENTS This study was made possible by the cooperation of many people. Special thanks are due the family of the late R, Bourke MacDonald For the many services and information that were provided throughout the study. I would like to thank Dr. John J. Craighead, advisor and com mittee chairman, for initiating the study, providing many valuable suggestions, assistance, and guidance during all phases of the study. To Drs. L, E. Eddleman and R. R. Ream, I extend my thanks for valuable information and assistance in the formulation of the range study and review of the manuscript. Dr. B. W. O'Gara spent many hours reviewing manuscript drafts as well as providing suggestions for field work , For their advice and assistance, I extend my gratitude to the following: Drs. W. L. Pengelly and P. L. Wright, Mr. Kenneth Greer, Mr. Pat Patterson and fellow students John Hechtel, Charles Kay, and all who aided in the census work. The study was funded by the Montana Cooperative Wildlife Research Unit.* * Bureau of Sport Fisheries and Wildlife, Montana Fish and Game Depart ment. University of Montana, and Wildlife Management Institute Cooperating ; ii TABLE OF CONTENTS Page LIST OF TABLES ................................................... v LIST OF FIGURES ................................................. vi Chapter I. INTRODUCTION .......................................... 1 II. STUDY A R E A ............................................ 4 Location and Description ............................ 4 Climate ............................................... 6 Land Ownership and U s e .............................. 6 III. M E T H O D S ................................................ 13 Range Study .......................................... 13 Sheep Study .......................................... 13 IV. RESULTS ................................................ 15 Range Study .......................................... 15 Subtype Description .................................. 15 V. DISCUSSION ............................................ 37 M o r t a l i t y ............................................. 37 Mortality Factors .................................... 38 N a t a l i t y ............................................. 42 Recommendations...................................... 43 Management Options .................................. 43 VI. S U M M A R Y ................................................. 46 LITERATURE CITED ................................................. 48 iii Iv Page APPENDIX I Vegetatlonal Data for Wlldhorse Island .......... 50 la Vegetatlonal type Map of Wlldhorse Island ............ 51 Ib Vegetatlonal Subtypes with Corresponding Community Mapping Number, Acreages, and Dominant Forage Species . 52 Ic Plant L i s t ............................................ 56 Id Results of Subtype Sampling (by square foot plot) . • . 60 APPENDIX II Census and Activity D a t a ......................... 69 I la Censuslng Map of Wlldhorse I s l a n d ................... 70 Ilb Six Dally Activity Patterns of Mountain Sheep on Wlldhorse Island ...................................... 72 APPENDIX III Mortality Data Concerning Mountain Sheep on Wlldhorse Island, 1971— 72 •••• 78 Ilia Locations of Mountain Sheep Mortalities, Winter 1971-72 ............................................... 79 m b List and Location of Parasites Found In Winter-killed Rams from Wlldhorse Island, 1971-72 ................. 81 IIIc Host—Parasite Data Sheets ............................ 82 Illd Skull and Horn Weights, In Grams, of Winter-killed Rams from Wlldhorse Island, 1971-72 ................. 86 Ille Horn Measurements, In Millimeters, of Winter-killed Rams from Wlldhorse Island, 1971— 72 ................. 87 LIST OF TABLES Table Page 1* Average Maximum, Minimum and Monthly Temperatures (in degress Fahrenheit) for Flathead Lake ................... 7 2. Average Percent Cover (basal area) of Sampled Subtypes, in Square F e e t ........................................... 18 3. Summary of Acreages and Percentages of Plant Communities (classified by dominant species) by Percent Class Use • • 22 4. Best Count Summary of Mountain Sheep on Wildhorse Island 1971-72 ................................................... 23 5. Sex and Age Distribution of Overwinter Mortality of Bighorn Sheep on Wildhorse Island 1971-72 ............... 27 6. Summary of Total Mortality of Bighorn Sheep on Wildhorse Island May, 1971-January, 1973 28 7. Sex and Age Specific Life Table Based on 67 Known-Age Mortalities of Mountain Sheep on Wildhorse Island 1971-1972 ................................................. 29 8. Age Classification of Free Roaming Bighorn Rams by Annualation Count ........................................ 30 9. Bone Marrow Samples of Winter-killed Bighorn Sheep 1971-1972 ................................................. 31 10. Rumen Analyses of Six Rams Found as Winter and Spring Mortalities 1971-1972 Expressed in Percent Volume .... 32 LIST OF FIGURES Fig. Page 1. Location of Wildhorse Island .............................. 5 2. Abundance of Major Grazing Populations on Wildhorse Island 9 3. Vegetatlonal Use Map of Wildhorse Island ........... 11 4. Seasonal Distribution Map of Wildhorse Island ........ 12 5. Vegetatlonal Community Map of Wildhorse Island............ 16 6. Lamb Production on Wildhorse Island During 1971 and 1972 . 24 7. Activity Patterns of Bighorn Sheep Based on Six Daylight Observations ............................................... 36 8. Sex and Age Specific Death Curve for Male and Female Bighorn Sheep of Wildhorse Island ....................... 40 vi Chapter I INTRODUCTION . Wildhorse Island, Flathead Lake, Montana, provides a situation in which two big—game species. Rocky Mountain bighorn sheep (Ovis canadensis canadensis) and mule deer (Odocoileus hemionus hemionus), are found within the confines of an Island habitat. One horse and one mule are also present on the Island, Other mammals such as coyotes (Canis latrans) , badgers (Taxidea taxus) and porcupines (Erethizon dorsatum) inhabit the Island, During an occasional harsh winter, ice allows some interchange with the mainland; however, this interchange is limited largely to deer and coyotes, Couey (Buechner, 1960) discussed seven transplants of Rocky Mountain bighorn sheep made in Montana, At least five of these appeared to have become established, one being on Wildhorse Island. The history of the bighorn sheep population on the Island is documented; a male and female, both yearlings, were introduced onto the Island in 1939. Their origin is uncertain; Ogren (1954) indicated that they were caught as lambs in the Mission Mountains and subsequently released on the Island. There is some feeling however, that the original stock may have come from the Sun River area (Pengelly, pers. comm.). In 1947, the Montana Fish and Game Department made one addi tional transplant of three adult females and three males (one 2 year old and two older males). Those animals introduced in the second 2 transplant were from Sun River Canyon (Ogren, Ibid.). At that time, the minimum size of the population was estimated at 12 animals (Ogren, Ibid.). The present herd, estimated at 240 individuals in 1972, grew from that small nucleus. During the same period, many other mountain sheep populations declined. Berwick (1968) documented the decline of the Rock Creek, Montana, sheep population. Morgan (1970) reported that bighorn sheep herds in the Challis, Idaho, area were on the decline- During the early 1950's, Smith (1954), found sheep populations to be on the increase in Idaho, but indicated that they were subject to periodic