Drought and coyotes mediate mesopredator response to human disturbance

Mesopredators in western North America are facing major changes to their
ecosystems, including drought and the expansion of human disturbance. To
balance resource needs and risk-taking on the landscape, mesopredators are
likely shifting their habitat use as well as their interspecies
interactions. As part of a large-scale study to help evaluate responses of
terrestrial wildlife to severe drought, the California Department of Fish
and Wildlife surveyed mesopredator presence across 585 sites in the Mojave
Desert and Central Valley ecoregions of California. This study spanned a
drought year (2016) and a post-drought year (2017), providing the
opportunity to investigate how drought and interspecific interactions may
mediate spatial patterns of mesopredator occurrence across a continuum of
human disturbance levels. We used single-season, single-species, and
conditional two-species occupancy models to elucidate these relationships
in both ecoregions. We examined occupancy and detection of coyotes (Canis
latrans) and smaller mesopredators, including bobcats (Lynx rufus) in both
ecoregions, raccoons (Procyon lotor) in the Central Valley, and desert kit
foxes in the Mojave Desert (Vulpes macrotis arsipus). The presence of
coyotes influenced the detection probability of all other mesopredator
species, and the impacts of drought varied by species and ecoregion.
Detection of mesopredators in the Central Valley was typically higher in
2016, especially at low disturbance sites, suggesting species may have
become more active during the drought to meet resource needs. However,
detection of mesopredators in the Mojave Desert tended to increase after
the drought, suggesting a response to an increase in resources (e.g.,
prey). Coyotes in the Mojave Desert became more detectable in high human
disturbance in 2016 and less detectable in 2017, possibly increasing
activity during the drought in human-disturbed areas to obtain
anthropogenic resources. Drought not only affects individual species and
their relationships to human disturbance, but it can also impact their
interspecies interactions and use of different landscape features.