THE EFFECTS OF SPRING CATTLE GRAZING ON THE NUTRITIONAL ECOLOGY OF MULE DEER (ODOCOILEUS HEMIONUS) IN EASTERN WASHINGTON By SARA JANE WAGONER A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCES IN NATURAL RESOURCE SCIENCES WASHINGTON STATE UNIVERSITY Department of Natural Resource Sciences MAY 2011 To the Faculty of Washington State University The members of the Committee appointed to examine the thesis of SARA JANE WAGONER find it satisfactory and recommend that it be accepted ________________________________ Lisa A. Shipley, Ph.D., Chair ________________________________ Linda H. Hardesty, Ph.D. ________________________________ Kristen A. Johnson, Ph.D. ________________________________ Karen L. Launchbaugh, Ph.D. ii ACKNOWLEDGEMENTS This project was fully funded and supported by the Washington Department of Fish and Wildlife (WDFW), and partnered by the Washington Cattlemen’s Association. My advisor, Dr. Lisa A. Shipley, whom was the brain-child and brawn-child behind this enormous endeavor, tirelessly offered perspective and assistance when I needed it, and I am forever indebted. A sincere thank you to my committee members: Linda Hardesty, Kristen Johnson, and Karen Launchbaugh for contributing their range science expertise and logistical input to our experimental design. I extend my appreciation to Rachel and John Cook, for giving me the opportunity to work along side them at Starkey; it gave me a real grasp on what I was getting into; especially to Rachel, for her professional guidance, friendship, and assistance towards this project. Thank you Laura Applegate, Taryn Clark, Becky Greenwood, Ben Maletzke, Tamara Johnstone-Yellin. and Sarah McCusker for selflessly pitching in, you are truly great friends. And, to the wonderful WDFW employees, especially to Bob Dice, for taking care of us graduate students, we are helpless at times. Curt and Jaime Creson, Sam “wise” Huset-Dwinell, Jeremy Brown, Meghan Camp, Ellen Miller, Elise Olk, Rachel Ambrosen, and Rachel Grandberg, assisted with the data collections and put up with me, I wouldn’t have. And to my deer friends, Sydney, Rogue, Cherry, Tea, and Lily, if only you could speak; to this day, I still dream of counting bites of P. spicata and T. dubius. To my husband and best friend, Brandon Rogers for all his encouragement, love, and altruistic computer services. And to my wonderful mother, if not for her, I wouldn’t be here; especially, for her loving support, hugs, and superb cooking skills. iii THE EFFECTS OF SPRING CATTLE GRAZING ON THE NUTRITIONAL ECOLOGY OF MULE DEER (ODOCOILEUS HEMIONUS) IN EASTERN WASHINGTON Abstract by Sara Jane Wagoner, M.S. Washington State University May 2011 Chair: Lisa A. Shipley In some grassland communities, livestock grazing may reduce residual grass and promote younger, more nutritious forages. However, no study has yet directly examined how spring cattle grazing affect the quantity and quality of forage available to mule deer (Odocoileus hemionus). Therefore, we created 2-sets of 3 plots of paired grazing treatments using electric fence exclosures within 3 pastures in bluebunch wheatgrass (Pseudoroegneria spicata) communities in southeastern Washington. In each grazed/ungrazed plot, we sampled the biomass and nutritional quality of all plants by species in both spring and fall. We constructed temporary pens in each grazed/ungrazed plot and measured diet composition selected by 4 tractable mule deer in each pen using bite count methods, collected representative diets for each deer in each plot, and analyzed them for digestible nitrogen and protein in spring and fall. In spring and fall, grazed pastures had 40% less total biomass, and significantly less perennial grasses and perennial forbs. As a consequence, across seasons, deer consumed about 40% less perennial and annual forbs, and 30% more perennial grasses grazed pens. Using Ivlev's selectivity index, we found that deer selected for iv annual forbs and subshrubs and avoided perennial and annual grasses. The dry matter digestibility and digestible energy of the deer's diets was similar between grazed and ungrazed plots, but digestible protein was higher in grazed plots in 2 pastures and lower in the third on than on grazed plots. Deer cropped larger bites (g/bite) in ungrazed plots than grazed plots in fall, had a higher instantaneous intake (g/min) in ungrazed plots in one pasture, and had a higher daily dry matter intake (g/day) and daily digestible energy intake (kJ/day) in ungrazed than grazed plots across pastures and seasons. Because biomass of forage was reduced up to 50% in grazed plots, while nutritional quality of forages, including P. spicata increased modestly, if at all, nutritional carrying capacity for deer was lower in grazed than ungrazed plots in 2 of the 3 pastures. Our results suggest that moderate spring cattle grazing in dry-stony ecological sites reduced the amount of digestible nutrients available to mule deer during the year of grazing. v TABLE OF CONTENTS ACKNOWLEDGEMENTS ...............................................................................................iii ABSTRACT .....................................................................................................................iv LIST OF TABLES.......................................................................................................... viii LIST OF FIGURES..........................................................................................................ix INTRODUCTION............................................................................................................. 1 MATERIALS AND METHODS ........................................................................................ 5 Study area............................................................................................................... 5 Experimental design................................................................................................ 7 Treatments.............................................................................................................. 9 Biomass, composition, and nutrition of available forages........................................ 9 Diet composition and foraging behavior of mule deer ........................................... 11 Diet selection of mule deer.................................................................................... 13 Nutritional quality of forages and mule deer diets. ................................................ 14 Nutrient intake of mule deer .................................................................................. 15 Nutritional carrying capacity for mule deer ............................................................ 15 Statistical analyses................................................................................................ 16 RESULTS...................................................................................................................... 17 Preliminary analyses of study sites ....................................................................... 17 Biomass and composition ..................................................................................... 18 Nutritional quality of forages and carrying capacity ............................................... 20 Deer diet composition and selection ..................................................................... 22 Diet quality and nutrient intake of deer.................................................................. 25 vi DISCUSSION................................................................................................................ 26 Forage biomass and intake rate of mule deer ....................................................... 27 Diet quality, nutrient intake rate, and carrying capacity ......................................... 30 APPENDICES ............................................................................................................... 80 Appendix A: SPECIES LIST.................................................................................. 81 vii LIST OF TABLES 1. Cattle grazing schedule and sampling dates......................................................... 40 2. Changes in biomass and species composition by grazing treatment .................... 41 3. Nutrient of common forbs and grasses.................................................................. 42 4. Diet composition and selection.............................................................................. 43 5. Nutrient content of mule deer diets ....................................................................... 44 6. Deer activity budgets............................................................................................. 45 7. Nutrient intake rates by treatment and season...................................................... 46 viii LIST OF FIGURES 1. Study area map ................................................................................................................. 47 2. Average monthly precipitation......................................................................................... 48 3. Average monthly temperature......................................................................................... 49 4. Diagram of experimental design .................................................................................... 50 5. Pellet group transect layout ............................................................................................. 51 6. Pellet