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Assessing the Use of Social Calls to Attract Bats to Artificial ASSESSING THE USE OF SOCIAL CALLS TO ATTRACT BATS TO ARTIFICIAL ROOST SITES By Alyson Frances Brokaw A Thesis Presented to The Faculty of Humboldt State University In Partial Fulfillment of the Requirements for the Degree Master of Science in Biology Committee Membership Dr. Joseph Szewczak, Committee Chair Dr. Jeffrey Black, Committee Member Dr. Sharyn Marks, Committee Member Dr. Elizabeth Whitchurch, Committee Member Theodore Weller, Committee Member Dr. Michael Mesler, Graduate Coordinator May 2015 ABSTRACT ASSESSING THE USE OF SOCIAL CALLS TO ATTRACT BATS TO ARTIFICIAL ROOST SITES Alyson Frances Brokaw Many conservation strategies for bats focus on supporting or enhancing their roosting and foraging needs. With increasing urbanization and loss of natural habitat, many species have adapted to roost in anthropogenic structures, resulting in increased human-wildlife conflict. Bat boxes can provide alternate housing for bats displaced due to exclusions from anthropogenic structures or loss of natural roosts. Researchers and conservationists have begun to investigate the variety of cues bats use to locate and select possible roost locations, such as visual, olfactory or auditory cues. In this study, I describe the call structure of social calls emitted by Yuma myotis (Myotis yumanensis) at roost sites. I investigated if free-ranging Yuma myotis react to social calls of conspecifics and other bat species at roost sites. I also evaluated the effects of age, sex and reproductive status on behavioral responses to social calls. In the summers of 2013 and 2014, I recorded calls from Yuma myotis using bat detectors mounted outside of roost exits. The recorded social calls divided into two distinct types that I could isolate and identify. Type 1 calls consist of a single frequency modulation (FM) syllable, while Type 2 calls consist of a descending FM sweep, finishing on a hook-shaped component. I broadcast social call and echolocation calls of Yuma myotis and Mexican free-tailed bats (Tadarida brasiliensis mexicana) from newly erected artificial roost sites. Bat activity ii was significantly higher during playbacks of myotis social calls compared to other playback treatments or silent control nights. Additionally, bat activity remained elevated after playback treatments, indicating a latent effect of playbacks at roosting sites. To test individual responses, bats were placed in a field flight tent and exposed to the same broadcast calls used in the field experiment. Individuals in a flight cage displayed no significant response to social calls, regardless of age, sex or reproductive status. This study provides the first description of social calls in a North American myotis species and suggests that understanding the social relationships of bats at roosting and foraging sites may be useful for informing conservation and management decisions. iii ACKNOWLEDGEMENTS This study would not have been possible without the support of many people. I would like to thank my advisor, Joseph M. Szewczak, for making this research possible, providing guidance and input throughout the length of my study and allowing access to detectors and other equipment. I’d also like to thank all the members of my committee, including Dr. Jeffrey Black, Dr. Sharyn Marks, Dr. Elizabeth Whitchurch and Theodore Weller for their advice and editing support. I would especially like to thank Ted Weller for providing training in bat capture and handling techniques. Thanks to The Benbow Inn for allowing me to install bat boxes and giving access to their property for my research, as well as a having a genuine interest in bat conservation. I’d also like to thank Erinn Trujillo of Umpqua National Forest, U.S. Forest Service; Patrick Doyle of Van Duzen County Park, Humboldt County Department of Public Works; Jay Harris of California State Parks, North Coast Redwoods District; David Anthon of Headwaters Forest Reserve, Bureau of Land Management; and Desiree Early of Green Diamond Resource Company for allowing me access to field sites for field playback and bat captures. Thanks to Jeffrey Clerc for countless hours of discussion, field assistance, statistics advice and moral support throughout the past year. Additional thanks for field assistants and volunteers Bern Fahey, Matthew Scott, Christen Long and Cari Zourdos Williams. This entire journey would not have been possible without a lifetime of support from my parents William and Patricia Brokaw, who encouraged me to reach my full potential and instilled a love for the environment, wildlife and science at an early age. Also, thanks to my sister Julia Brokaw, for always being my biggest cheerleader in everything. Finally, iv infinite thanks to my husband Bradley Bogdan, for putting up with my being away for long days and late nights in the field, keeping the house running while I holed away writing and always being there for me. This study would not have been possible without funding from several local and national organizations, including Humboldt State University Master’s Grant, Bat Conservation International Student Scholarship, American Society of Mammalogists Grant-in-Aid of Research and California North Coast Chapter of The Wildlife Society. v TABLE OF CONTENTS ABSTRACT ........................................................................................................................ ii ACKNOWLEDGEMENTS ............................................................................................... iv LIST OF TABLES ........................................................................................................... viii LIST OF FIGURES ........................................................................................................... ix INTRODUCTION .............................................................................................................. 1 MATERIALS AND METHODS ........................................................................................ 6 Study Species .................................................................................................................. 6 Study Sites ...................................................................................................................... 7 Focal Roosts ................................................................................................................ 7 Capture Locations ....................................................................................................... 9 Collecting and Isolating Social Calls .............................................................................. 9 Field Playback Experiment ........................................................................................... 13 Statistical Analysis .................................................................................................... 16 Individual Playback Experiment ................................................................................... 17 Behavioral Responses ............................................................................................... 20 Statistical Analysis .................................................................................................... 21 RESULTS ......................................................................................................................... 22 Social Calls in Myotis yumanensis ................................................................................ 22 Field Playback Experiment ........................................................................................... 25 Individual Playback Experiment ................................................................................... 34 DISCUSSION ................................................................................................................... 39 Social Calls in Myotis yumanensis ................................................................................ 39 vi Field Playback Experiment ........................................................................................... 43 Individual Playback Experiment ................................................................................... 48 CONCLUSION ................................................................................................................. 51 Literature Cited ................................................................................................................. 52 vii LIST OF TABLES Table 1. Social call parameters of Yuma myotis from northern California, showing Type 1 (n = 19) and Type 2 (n = 50), values of t-statistic and corresponding levels of significance P. For each parameter the value for Type 2 calls is given below that for Type 1 calls. Q1 and Q3 are the lower and upper quartiles. ...................................................... 24 Table 2. Wilcoxon matched pairs test for pairwise comparisons of the numbers of bat approaches combined and separately for each type of approach between five treatments, the W- test statistic and corresponding P value. ............................................................... 30 Table 3. Wilcoxon matched pairs test for pairwise comparisons of the numbers of bat approaches combined and separately for each type of approach between four treatments (MYYU social calls and echolocation calls combined into one treatment), the W- test statistic and corresponding P value................................................................................... 33 viii LIST OF FIGURES Figure 1. Top, Example sonogram of a
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