Drought and coyotes mediate the relationship between mesopredators and human disturbance in California

Author

Molly K. ParrenFollow

Graduation Date

Fall 2019

Document Type

Thesis

Program

Master of Science degree with a major in Natural Resources, option Wildlife

Committee Chair Name

Barbara Clucas

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Daniel Barton

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

William T. Bean

Third Committee Member Affiliation

HSU Faculty or Staff

Keywords

Mesopredator, Coyote, Canis iatrans, Drought, Human disturbance, California, Central Valley, Mojave Desert, Occupancy, Detection, Species interactions, Co-occurrence, Refuge

Subject Categories

Wildlife

Abstract

Mesopredators in California are facing two major changes to their ecosystem: drought and the expansion of human disturbance. As a result, mesopredators are likely shifting their habitat use as well as their interspecies interactions to balance resource needs and risk-taking on the landscape. In response to severe drought, the California Department of Fish and Wildlife deployed 585 camera traps throughout the Mojave Desert and Central Valley documenting mammalian mesopredator presence in a drought year (2016) and a post-drought year (2017). The objectives of this study were to examine spatial patterns of mesopredator occurrence and co-occurrence with a dominant predator, the coyote (Canis latrans), at a large spatial scale across varying levels of human disturbance and to investigate how drought may mediate these relationships. Single-season, single-species occupancy models were used to elucidate the relationship between human disturbance, drought, and mesopredator habitat use in both ecoregions. Conditional two-species occupancy models were then fit to establish the effect coyotes may have had on subordinate mesopredators and their relationships with human disturbance during and after the drought. I found that human disturbance differentially affected both the occupancy and detection of mesopredator species and that these relationships were sometimes mediated by drought and the presence of coyotes. Except for the domestic cat (Felis catus), all mesopredators showed some kind of response to drought. Detection of mesopredators in the Central Valley was typically higher in 2016, especially in low disturbance sites, indicating that species became more active during the drought to meet resource needs. However, detection and occupancy of mesopredators in the Mojave Desert tended to increase after the drought, suggesting that species were responding to an increase in resources, possibly the density of prey. Coyotes in the Mojave Desert became more detectable in high human disturbance in 2016 and less detectable in 2017, signifying that they were increasing activity in human disturbance during the drought, possibly to obtain anthropogenic resources. Additionally, subordinate species, particularly in the Central Valley, appeared to take greater risks during the drought with increased use of water sources, despite the presence of coyotes. These findings suggest that drought not only affects individual species and their relationships to human disturbance, but that it can also impact their interspecies interactions and use of different landscape features.

Citation Style

Journal of Wildlife Management

Recommended Citation

Parren, Molly K., "Drought and coyotes mediate the relationship between mesopredators and human disturbance in California" (2019). Cal Poly Humboldt theses and projects. 349.
https://digitalcommons.humboldt.edu/etd/349