Graduation Date
Fall 2019
Document Type
Thesis
Program
Master of Science degree with a major in Natural Resources, option Wildlife
Committee Chair Name
Dr. Barbara A. Clucas
Committee Chair Affiliation
HSU Faculty or Staff
Second Committee Member Name
Dr. William T. Bean
Second Committee Member Affiliation
HSU Faculty or Staff
Third Committee Member Name
Dr. Daniel C. Barton
Third Committee Member Affiliation
HSU Faculty or Staff
Fourth Committee Member Name
Dr. Joseph M. Szewczak
Fourth Committee Member Affiliation
HSU Faculty or Staff
Keywords
Bat, Central Valley, Agriculture, Human disturbance, Human land use, Occupancy modeling, Bat acoustic monitoring, Orchards
Subject Categories
Wildlife
Abstract
California’s Central Valley, one of the most productive agricultural regions in the world, is home to 14 species of resident and migratory bats. The Central Valley has been identified as a crisis ecoregion, and a high number of species are at risk due to anthropogenic land use. In addition, the Central Valley has faced severe drought, effects of which are intensified on the natural landscape by agricultural irrigation practices. In response to the historical drought of 2012-2015, California Department of Fish and Wildlife (CDFW) implemented the Terrestrial Species Stressor Monitoring (TSSM) project, which in part aimed to collect information on baseline occupancy data and habitat associations for bats. Bat surveys were conducted using SM3BAT acoustic detectors at 274 sites spanning the Central Valley in both the driest (2016) and wettest years on record (2017). The objectives of my thesis were to determine (1) Do anthropogenic land use and drought influence bat occupancy at a landscape level? If so, do bats use anthropogenic land types more during the drought? (2) Do anthropogenic land use and drought affect bat species differently based on habitat specialization? I hypothesized that bat occupancy would be greater in agricultural areas during the drought, anthropogenic land use would predict the distribution patterns of habitat specialists, and occupancy for all species would be lower during the drought. This data collection effort resulted in the largest bat acoustic survey of the Central Valley with 14 species detected and over 3,300 species-site-night events. I fit single-species occupancy models in a Bayesian framework, using environmentally or biologically relevant covariates. Using these models, I generated range wide occupancy predictions for individual species and total species richness. Migratory species contracted their geographic range during the drought, while hibernating species did not. Further, arid-adapted species expanded from natural open areas into cultivated landscapes during the drought. The results of this thesis suggest that migratory species may more easily adapt to drought conditions, irrigated agricultural areas may act as drought refugia, and large-scale acoustic studies can serve as an alternative or supplement to capture for acoustically detectable bat species.
Citation Style
Journal of Wildlife Management
Recommended Citation
Smith, Trinity N., "Elucidating patterns of bat species occupancy across a disturbed landscape in California's Central Valley" (2019). Cal Poly Humboldt theses and projects. 354.
https://digitalcommons.humboldt.edu/etd/354