However, the rare Sierra Nevada red fox (Vulpes vulpes necator), is native.
Did you know, Vulpes vulpes was introduced to California in the 1880’s? They are now threatening several endangered ground bird species. Different programs have been tried to manage them.
I never realized there was a native and non-native Red Fox in California. The other species of foxes, such as Gray, Island, and Kit fox are native, I believe. I read about introduced species in the great book “National Audubon Society Field Guide to California.”
Here’s a map of iNat observations of Red Foxes in North America, with records for the overall species, the four native subspecies and the introduced V. v. crucigera.
It looks like there is definitely some scope for someone with good ID skills to clarify IDs for some of these observations. In particular, can a subspecies ID be confidently made for the species-level observations within and around the ranges of native red foxes?
Actually, recent studies indicate that while European foxes were introduced to the Americas, few of them, if any, made any actual inroads into the population (most of this research happened within the last 20 years, hence why the cited paper still assumes the introduced foxes are solely European). The introduced foxes in California are now considered to be the Eastern red fox (V. v. fulvus).
I don’t know much about this situation but it sounds slightly unbelievable to me that a subspecies that only split ~15.000 years ago would have a drastically different impact on native species than its close relative, to such an extent it drives them to extinction. Are you sure this isn’t one of those cases where ground birds aren’t doing well because of other - human - pressures and the predator is scapegoated?
It’s quite likely that there were no Red Foxes of any subspecies in most of California – the deserts in the eastern part of the state alone make a pretty good barrier to dispersal. So the issue of which subspecies is present now would have no bearing on the impacts on native species.
It does seem that a lot of the lowland red foxes in California may be Eastern red fox (V. v. fulvus) and not the European V. v. crucigera.
To complicate things, there’s also this report from 2010 that identifies a native Sacramento Valley red fox with distribution from the Delta north almost as far as Redding plus a hybrid population on the southern and eastern edges of this range. The figures from page 35 in that report provide a lot of detail.
The same team formally described the Sacramento Valley red fox as the new subspecies Vulpes vulpes patwin in a separate 2010 paper.
No, the High Sierra Red Fox is a predator at very high elevations. The High Sierra is a world apart from the lowlands of California. Thus, an introduction to the lowlands of the Eastern Red Fox is like Predator from another planet and the Native prey are not equipped to evade them.
Also, there’s a hybridization concern, mainly between the Sacramento Valley red fox and Eastern red fox in the area around the Sacramento delta and in the Sierra foothills.
Good stuff, thanks for the information. I’ve learned the San Joaquin Kit Fox (Vulpes macrotis ssp. mutica) is another native threatened species of concern. Their structure resembles the Red Fox, so I would caution myself on identifying Vulpes sp. unless I was very knowledgeable, or got the hang of their features and coloration.