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Distribution of nonnative red foxes in East Bay oak woodlands.

European red foxes (Vulpes vulpes) were introduced into lowland California in the 1880s for fur farming and hunting. The introduced foxes quickly spread throughout much of the state and have been implicated in the decline of several federally threatened and endangered ground-nesting bird species. Red foxes have been present in the East Bay for 25 to 30 years and they are regularly sighted in coastal wetlands and in the Oakland and Berkeley hills. We were interested in documenting the extent of the invasion away from human-dominated habitats into oak woodlands in the East Bay, as foxes may negatively impact both prey populations and native carnivores such as gray foxes. We surveyed fire roads and hiking trails in core oak woodland sites in Contra Costa and Alameda counties for carnivore scat. All scat samples were collected, and their locations entered into a GIS. To positively distinguish the scat to species, DNA was extracted, amplified, and identified using Polymerase Chain Reaction (PCR) and Restriction Fragment Length Polymorphism (RFLP) testing. Four carnivore species were identified, including coyote, gray fox, red fox, and bobcat. Red foxes were only detected in woodlands that were adjacent to urban or suburban development, and were not detected in more rural sites. They may be dependent on human-dominated systems for resources and cover, and the high numbers of coyotes present in the East Bay may be excluding them from some areas. This research is providing managers essential information about red fox distribution, habitat requirements, and interactions with other carnivores, which can be used to better monitor and eventually control red fox invasions and subsequent impacts to native species.