Phrynosoma Blainvillii) in the Southern San Joaquin Valley of California
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ECOLOGY AND DEMOGRAPHY OF THE BLAINVILLE'S HORNED LIZARD (PHRYNOSOMA BLAINVILLII) IN THE SOUTHERN SAN JOAQUIN VALLEY OF CALIFORNIA SUSAN MARIE HULT A Thesis submitted to the Department of Biology California State University, Bakersfield In Partial Fulfillment of the Degree of Masters of Science JUNE 2014 iii COPYRIGHT BY SUSAN MARIE HULT 2014 ii ECOLOGY AND DEMOGRAPHY OF THE BLAINVILLE'S HORNED LIZARD (PHRYNOSOMA BLAINVILLII) IN THE SOUTHERN SAN JOAQUIN VALLEY OF CALIFORNIA Susan M. Hult This thesis has been accepted on behalf of the Department of Biology by their supervisory committee: Dr. David J. Germano Committee Chair Dr. Steve Laymon Dr. Brandon Pratt iv ACKNOWLEDGEMENTS I would sincerely like to thank my advisor, Dr. David Germano, for his patience throughout the entire processes of coursework, research, fieldwork, and writing that resulted in the completion of my degree. His professional support in the realms of writing, statistical analysis, and editing has been invaluable. I also truly appreciate Dr. Stephen Laymon, who has proven to be an incredible source of moral, professional, and field support at Atwell and in the capacity of serving on my committee. I likewise thank Dr. Brandon Pratt for his ideas, friendly support, and review of my manuscript, which added greatly to the integrity of this thesis and for serving on my committee. Without the Bureau of Land Management's (BLM) Student Career Experience Program, I most likely would not have been able to carry out this research and obtain my degree. I hope (and believe) this research serves as a valuable source of information in which they can use to make land management decisions beneficial for P. blainvillii conservation in the southern San Joaquin Valley. I am extremely grateful for the strong support of my colleagues and supervisors at the BLM: John Skibinski, Steve Larson, Peter DeWitt, Denis Kearns, Amy Kuritsubo, Joaquin Martinez, and Larry Saslaw. They provided invaluable technical and field expertise as well as assisted in tracking and data gathering, of which I particularly appreciated during the nocturnal hours! I had excellent assistance from Dana Gasper, Teresa O'Keefe, and Natalie Montague who were willing to give large amounts of their time to gather telemetry, demographic, morphologic, and habitat data for this study. Without their assistance, the data would not be as robust as it is. Finally, the support of friends and family members truly kept me afloat whether they were nearby or 3,000 miles away at home in Minnesota. The support of loved ones was just as, if not v more so, crucial to the journey as professional support was, even if some of them had no idea what a "horny toad" is! vi ECOLOGY AND DEMOGRAPHY OF THE BLAINVILLE'S HORNED LIZARD (PHRYNOSOMA BLAINVILLII) IN THE SOUTHERN SAN JOAQUIN VALLEY OF CALIFORNIA Susan M. Hult Department of Biology, California State University, Bakersfield ABSTRACT The Blainville's Horned Lizard (Phrynosoma blainvillii) is endemic to California and ranges from northern California (Butte County), to the northwestern tip of Baja California in the southern part of its range, west of the Sierra Nevada Mountains and the southern California deserts in the eastern part of its range, and along the Pacific coast from northern Baja California to Monterey, California in the western part of its range. Phrynosoma blainvillii is listed as a California Species of Special Concern and a Bureau of Land Management (BLM) Sensitive Species. Human activities have been primarily responsible for declines in populations. There has been few field research studies published on the general ecology of P. blainvillii, particularly in the San Joaquin Valley. I initiated a radio-telemetry study to collect data on home range size and habitat use at two sites (Atwell Island and Semitropic Ridge Preserve) in the southern San Joaquin Valley, California. I calculated home range size from 10 lizards, five at each site. Using the 100% Minimum Convex Polygon (MCP) estimator I found home range sizes were between 0.58 ha to 13.93 ha, with an average size of 4.98 ha (± 1.54). When above ground and active, P. blainvillii at either site used areas of bare ground more often than expected based on equal use. At the Semitropic site, the lizards used areas under shrubs almost as often as bare ground, while at the Atwell site the lizards used areas of sparse vegetation more often than expected, but not as much as bare ground. Lizards at both sites used medium-dense and dense areas of vegetation much less than expected based on equal use. In adult P. blainvillii, we recorded a moderately skewed sex ratio of more males than females, but in young P. blainvillii, there were more females than males. Average snout-vent length (SVL) of females was 72.31 mm and for males 68.81 mm. The adult horned lizards were most active in April and May while young horned lizards were most active in August and September. In the spring, the morning activity hours peaked at 0900–1100, in summer, it was 0900–1000, and in fall, it was 0900–1300. All age classes of P. blainvillii were most often above ground and active at surface temperatures of 28– 34°C. The presence of alkali flats and sandy soil correlated with a high abundance of horned lizards, and within our two study locations, they revealed a distinct preference for Sandridge loamy fine sand over other available soil types. The lizards used kangaroo rat burrows rather than shrubs for heat refugia but used shrubs frequently as an escape from predators. Food items found in scats were predominantly ants, but beetles and other arthropods were also found in large numbers. vii TABLE OF CONTENTS CHAPTER 1. INTRODUCTION ............................................................................................ 1 Literature Cited ...................................................................................................................... 17 CHAPTER 2. HOME RANGE AND HABITAT USE OF THE BLAINVILLE’S HORNED LIZARD (PHRYNOSOMA BLAINVILLII) IN THE SOUTHERN SAN JOAQUIN VALLEY, CALIFORNIA ..... 23 Introduction ............................................................................................................................ 24 Materials and Methods ........................................................................................................ 27 Study sites ................................................................................................................................ 27 Field methods ........................................................................................................................... 30 Data analysis ............................................................................................................................ 33 Results ..................................................................................................................................... 36 Discussion ................................................................................................................................ 38 Literature Cited ...................................................................................................................... 45 CHAPTER 3. DEMOGRAPHICS, MORPHOLOGY, THERMOBIOLOGY, AND HABITAT PREFERENCE OF A POPULATION OF BLAINVILLE'S HORNED LIZARD IN THE SOUTHERN SAN JOAQUIN VALLEY, CALIFORNIA ................................................................................................................... 58 Introduction ............................................................................................................................ 59 Materials and Methods .......................................................................................................... 62 Study sites ................................................................................................................................ 62 Field data collection ................................................................................................................. 65 Demography and morphometrics ............................................................................................. 66 Activity ..................................................................................................................................... 67 Habitat assessment ................................................................................................................... 68 Statistical analysis .................................................................................................................... 68 Results ..................................................................................................................................... 70 Demography and morphometrics ............................................................................................. 70 Activity ..................................................................................................................................... 70 Habitat assessment ................................................................................................................... 71 Discussion ................................................................................................................................ 72 Literature Cited ...................................................................................................................... 79 CHAPTER 4. DIET ANALYSIS OF A POPULATION OF THE BLAINVILLE'S HORNED LIZARD (PHRYNOSOMA BLAINVILLII) FROM THE SOUTHERN SAN JOAQUIN VALLEY, CALIFORNIA,