Introduction and Range Expansion of Nonnative Red Foxes (Vulpes vulpes) in California

North American montane red foxes: expansion, fragmentation, and the origin of the Sacramento Valley red fox

“…The anomalous nature of the semi-desert habitat conditions in the Sacramento Valley relative to the subalpine and alpine habitats occupied by native montane red foxes in the western contiguous US led to early speculation that this population may have been introduced (Grinnell et al 1937). This belief later appeared to be supported by a morphometric study, which demonstrated that Sacramento Valley foxes were significantly larger than montane foxes but similar in size to Midwestern foxes (Roest 1977), suggesting that exotic red foxes could have been transported to the Valley via transcontinental railway, after it reached the city of Sacramento in 1869 (Roest 1977;Lewis et al 1999;Kamler and Ballard 2002). However, recent mitochondrial analyses of historical and modern specimens from the Sacramento Valley indicated this population was distinct from other nonnative populations in California, which were clearly of Eastern and Northern origins (Perrine et al 2007;Aubry et al 2009).…”

“…These montane foxes are phylogenetically, morphologically, and ecologically distinct from red foxes native to eastern and northern North America (Roest 1977;Swanson et al 2005;Perrine et al 2007;Aubry et al 2009). In the 1900s, North American red foxes of Eastern and Northern ancestry were introduced to and have thrived in several warm, lowland regions of Washington, Oregon, and California (Aubry 1984;Lewis et al 1999;Kamler and Ballard 2002). Additionally, red foxes have occupied arid, lowland habitats in the Sacramento Valley of California since at least 1880, which predates both the earliest known fur farms and the establishment of other lowland and putatively introduced red fox populations in western North America (Grinnell et al 1937;Kamler and Ballard 2002).…”

“…Wolder, US Fish and Wildlife Service, personal communication). Moreover, populations that occupy the adjacent San Joaquin Valley to the south, which presumably originated primarily from nonnative fur-farm stock, have recently expanded their range and may come into contact with the Sacramento Valley population (Lewis et al 1999;Perrine et al 2007). Hybridization with these inbred, admixed, and invasive foxes would compromise the genetic integrity of the Sacramento Valley population, and could reduce their fitness through the loss of locally adapted alleles or disruption of coadapted gene complexes.…”

A Preliminary Range-Wide Distribution Model for the Sacramento Valley Red Fox

“…In contrast to other native western red foxes, which occur in highelevation subalpine environments dominated most of the year by snow cover, this subspecies is restricted to elevations below 150 m on the floor of California's Sacramento Valley (bounded on three sides by moun-tains), where summer temperatures frequently exceed 408C and winter temperatures rarely dip below freezing. The hot, arid environment in the Sacramento Valley is so anomalous that for nearly a century these native red foxes were presumed to stem from introduced foxes from the eastern United States and were thus misclassified as a nonnative species (Grinnell et al 1937;Roest 1977;Jurek 1992;Lewis et al 1999).…”

Sea-level rise and refuge habitats for tidal marsh species: Can artificial islands save the California Ridgway's rail?

“…Additional research is needed into alternatives to existing tidal refugia that facilitate survival rates equivalent those provisioned by hybrid Spartina, such as islands. Levees have replaced these natural features in most remaining San Francisco Bay marshlands while mammalian predators have proliferated in the highly urbanized landscape of San Francisco Bay (Foin et al 1997;Lewis et al 1999). Easily accessible terrestrial refugia may present rails with greater exposure to mammalian predators than flooded intertidal refugia, as seen in other waterbirds (Pierluissi 2010).…”