INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6” x 9” black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. UMI A Bell & Howell Information Company 300 North Zeeb Road, Ann A rbor MI 48106-1346 USA 313/761-4700 800/521-0600 THE EFFECT OF BROWN TREE SNAKE (BOIGA IRREGULARIS) PREDATION ON THE ISLAND OF GUAM'S EXTANT LIZARD ASSEMBLAGES DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of the Ohio State University By Earl William Campbell III, B.A., M.S. ***** The Ohio State University 1996 Dissertation Committee: Approved by Jonathon B. Bart, Adviser Thomas C. Grubb Adviser Thomas E. Hetherington Department of Zoology William M. Masters UMI Number: 9630865 Copyright 1996 by Campbell, Earl William All rights reserved. UMI Microform 9630865 Copyright 1996, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 ABSTRACT The effect of Brown Tree Snake (Boiga irregularis) predation on the lizards of Guam was quantified by contrasting lizard abundance, morphology, size, and behavior in two 1-ha plots of secondary forest from which snakes had been removed and excluded, versus two 1-ha control plots in which snakes were monitored but not removed or excluded. Resident snakes were removed with snake traps, and immigration was precluded by electrified snake barriers surrounding the treatment plots. I sampled lizards in all plots quarterly for a year following snake elimination in the treatment plots. Although the density of lizards in all plots was very high (mean of 13,210 lizards/ha in unmanipulated plots), lizard numbers significantly increased in the treatment plots (to approx. 19,650 lizards/ha). Results of systematic lizard population monitoring before and after snake removal suggest that the abundance of an introduced skink, Carlia fusca, increased significantly and the abundance of two species of gekkonids, Lepidodactylus lugubris (native) and Hemidactylus frenatus (introduced) increased substantially on snake free plots. No changes were observed in the abundance of Emoia caeruleocauda, a native skink. Additionally, the mean snout vent length of all lizard species increased in the treatment plots, but not in the control plots following snake removal. No behavioral changes were observed in lizard species. A second goal of this experiment was to determine the practicality of snake exclosures for endangered species repatriation and snake quarantine facilities for cargo and vehicles leaving island. These results suggest that large scale snake exclosures will be feasible after refinements are made to the barrier to reduce rat and typhoon damage. Dedicated to my family and Meg iv ACKNOWLEDGMENTS I would like to thank Thomas Fritts and Gordon Rodda of the Department of the Interior's National Biological Service (NBS) for their guidance and support throughout my dissertation. Each of these individuals had a strong personal commitment to the completion of a project which was a logistical, mental, physical, and emotional challenge. Without their efforts, as well as the efforts of those who directly aided in the construction of the snake exclosures and data collection, this project would not have been completed. I firmly believe that the vision and commitment that Thomas Fritts has had guiding the scope of brown tree snake research within the NBS sets a standard which others trying to deal with ecological catastrophes should follow. Tom's staunch commitment to the importance of the scientific method to gain insight into a politically sensitive topic where many would prefer a quick fix of questionable practicality is an example of his strengths. Gordon Rodda is one of the most insightful researchers I have ever encountered. Much of the strength of the data I report today is due to months of planning with Gordon prior to barrier construction, in addition to daily advice at a distance. Gordon is clearly one of today's eminent herpetologists whom people will refer to tomorrow. I am thankful that I had a chance to work with both Tom and Gordon. I am indebted to the aid and support of my advisor, Jonathan Bart at the Ohio Cooperative Fish and Wildlife Research Unit (OCFWRU). Jon provided me with a situation where I could follow my dreams and visions. Like many prospective graduate students, I interviewed at several programs. At one institution I interviewed with one of the "fathers" of a modern field in conservation science who told me that there was no future or reason to conduct research on introduced species problems on oceanic islands. I didn't take that advice and luckily was accepted at the Ohio State University (OSU). Jon's strengths in sampling design and biostatistics have aided in the clarification of trends in this data. His support and advice throughout this research has been of great value and I thank him for it. I wish to thank Jon Bart, Tom Fritts, and Gordon Rodda for reviewing many documents I have written over the last seven years. This has been a thankless task but has improved my writing abilities. Tom Hetherington should be recognized for his advice and thoughts during my tenure at OSU. He has aided with many details of this work. I would like to thank my dissertation committee members; Tom Fritts, Tom Grubb, Jr., Tom Hetherington, and Mitch Masters, for their advice and comments on the planning of research and reviewing this document. Craig Clark was the primary individual who aided me with my field research on a daily basis during my tenure on Guam. Craig's technical skills and high standards for fieldwork were a major factor in the success of this project. Craig not only worked with me on a daily basis but was my primary housemate while living on Guam. Muchos gracias. Heidi Hirsh, Environmental Officer, at the Andersen Air Force Base, Guam (AAFB) acted as a liaison for this research on Base. Heidi's coordination made the logistics of this research much easier. Her efforts made this work much easier. The Department of Defense should be thanked for allowing much ofthis research to be conducted on their property. I would like to thank Craig Clark, Rick Blakely, Tom Fritts, and Gordon Rodda for assistance with initial barrier testing. Logistical assistance for this aspect of my research was provided by Mike McCoid and the staff of the Division of Aquatic and Wildlife Resources (GDAWR) and Heidi Hirsh (AAFB). The construction of the snake barrier was done with the aid of several individuals. I would like to thank Craig Clark, Jay Graham, Matt Reid, Kerensa King, Gordon Rodda, Brendan McCarthy, and volunteers from AAFB for aid in construction of the barrier. Staff of the 633rd Civil Engineering Squadron and Explosive Ordnance Disposal Unit at AAFB aided in the clearing of plot perimeters. I would like to thank the following individuals who aided in the monitoring of snake and lizard populations on the snake free and snake present plots and maintenance of the snake barrier: Craig Clark, Jay Graham, Thomas Sharp, Grant Beauprez, Todd Mabee, Stan Kot, Greg Campbell, Marie Timmerman, Jo Ann White, Dave Worthington, Tom Fritts, Gordon Rodda, Pat Fritts, Ren6e Rondeau, and Kerensa King. Kelly Wollcott, John Sanchez, Leslie Morton and Rosemarie Concepcion of the United States Fish and Wildlife Service's Guam National Wildlife Refuge (USFWS-GNWR) should be thanked for their support during this research. The refuge provided office, laboratory, and storage space which was used during latter phases of this research. During my tenure on Guam logistical assistance in Ohio was provided by Diane Rano, Roxanne Shull and Jonathan Bart at the OCFWRU. Linda Wolfe and Michelle Hampton of the NBS, Washington D.C. provided logistical assistance through Tom Fritts's office. On Guam, I wish to thank friends who provided support in numerous ways to this project. Tim Sherwood (GDAWR) provided me with free housing for several months. Mike and Rebecca McCoid (GDAWR) were extremely supportive of my efforts during the first year of this work and are missed on Guam. Gary Wiles, Bob Beck, Bob Anderson, Tino Aguon, Kelly Brock, Mike Ritter, Marvin Aguilar, and Lillian Mariano of the GDAWR all provided advice and support during this project. Ernie Kosaka (USFWS-Honolulu) should be thanked for his continual support of this and other NBS brown tree snake research efforts. The following individuals in Guam and the Commonwealth of the Mariana Islands should be thanked for their friendship and advice while I lived on Guam: Eva Beyer, Rick Blakely, Kelly Clark, Dan Grout (USFWS-Rota), Doug Gomez, Annie Marshall, John Morton (USFWS-Guam), Jorge Phocas (USFWS-Guam), Kelvin and Thea Osbourne, and Dave Worthington.