Distribution of the Eastern Fox Squirrel (Sciurus niger) in Southern California

King, Julie L.; Sue, Min Chung; Muchlinski, Alan E.

doi:10.1894/rts-03.1

Cited by 12 publications

(19 citation statements)

References 14 publications

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“…The earliest sightings (1960s) were in the Pecan Grove neighborhood, where a number of respondents state the squirrels were initially released. Given their tendency to travel distances over 500 m (Koprowski 1994, Shepherd andSwihart 1995) and disperse at a rate up to 3.4 km per year (King et al 2010), we are not surprised that squirrels are now found throughout much of the Yuma metropolitan area (Figure 1). How the squirrels reached Yuma is still unclear.…”

mentioning

confidence: 91%

“…the squirrels expanded their range over the years, extending to the southeastern corner of the city (Figure 1), and apparently dispersed or were introduced into Somerton. Such a pattern of expansion through urban areas and orchards is common (King et al 2010, Frey et al 2013. The ability to persist in the Sonoran Desert appears due to synanthropic relationships that provide trees and food sources.…”

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confidence: 99%

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Eastern fox squirrel (Sciurus niger, Linnaeus 1758) introduction to the Sonoran Desert

Brady

Koprowski²,

Gwinn

et al. 2016

Mammalia

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The eastern fox squirrel, native to the eastern and midwestern United States, was recently documented in the Sonoran Desert in the vicinity of Yuma, Arizona, constituting the first state record for this species. We surveyed the people of Yuma to determine when and how the squirrels arrived. The squirrels were first observed in the 1960s, but may have been resident for a longer period. Since the 1960s, squirrels have spread throughout the city limits and extended south ~15 km into Somerton, Arizona. How the squirrels arrived is not clear, but must be the result of an introduction, as no nearby populations exist. The persistence of eastern fox squirrels in this unique habitat is due to synanthropic relationships.

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confidence: 91%

mentioning

confidence: 99%

Eastern fox squirrel (Sciurus niger, Linnaeus 1758) introduction to the Sonoran Desert

Brady

Koprowski²,

Gwinn

et al. 2016

Mammalia

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“…In the greater Los Angeles, CA area, native western gray squirrels (Sciurus griseus) are declining in number. The decrease in population size coincides with the introduction of the eastern fox squirrel from the eastern United States (King et al 2010). The eastern fox squirrel was first introduced to Los Angeles County in 1904 (Becker and Kimball 1947).…”

Section: Introductionmentioning

confidence: 98%

“…However, these squirrels can still be found in less disturbed open areas in the Los Angeles metropolitan area (King 2004). Over the 100+ years since introduction, S. niger has flourished in urban and suburban areas within Los Angeles, Orange, and Ventura Counties, expanding their distribution by 0.44-3.44 km/yr (King et al 2010). As the eastern fox squirrel continues to expand its distributional range, it is moving into many habitats occupied by the native western gray squirrel (King 2004).…”

Section: Introductionmentioning

confidence: 99%

Eastern Fox Squirrels and Western Gray Squirrels in Southern California

Muchlinski¹,

Gatza²,

Lewis³

et al. 2012

vertebrate_pest_conference

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Eastern fox squirrels have been introduced to many regions within the western United States including areas within California, Idaho, Montana, Oregon, and Washington. In California, fox squirrels have been introduced to San Francisco, Fresno, . The geographic range of the eastern fox squirrel has expanded greatly both through natural dispersal and additional intentional introductions by humans. The fox squirrel has replaced the native western gray squirrel in certain habitats while the two species coexist in other habitats. Western gray squirrels exist by themselves in a third type of habitat even though eastern fox squirrels have occupied adjacent habitat for about 30 years. Habitat Suitability Models (HSMs) have been used to predict the presence and/or abundance of a particular species within a habitat. Analysis of 9 habitat variables using Discriminant Analysis produced a HSM where replacement, coexistence, and exclusion habitats can be identified using only 3 of the 9 habitat variables: average height of ground cover, percent canopy cover, and percent of total trees that are deciduous. A field study underway for over two years at Rancho Santa Ana Botanic Garden in Claremont, CA is testing the validity of the HSM with the study site predicted to be a long-term coexistence habitat. The ratio of western gray squirrels to eastern fox squirrels has gone from 3:1 shortly after the fox squirrel entered the habitat to 1:1, but after 2.5 years of coexistence both species are commonly observed in the study site. The HSM is also being tested through the analysis of additional habitats. Although coexistence of the two species is possible for many decades, the number of western gray squirrels in coexistence habitats is often small, coexistence habitats are geographically isolated from each other, and the probability of extinction of western gray squirrels from these habitats could be high. We are also looking for new habitats which could support western gray squirrels if individuals were moved to these habitats.

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“…Fox squirrels have dispersed from original points of introduction through natural dispersal and through intentional movement of animals by humans (Frey & Campbell, 1997 ; Geluso, 2004 ; King et al, 2010 ). Since the original introduction to Los Angeles County (Becker & Kimball, 1947 ), the FS has expanded its range at a rate of 1.60 to 3.00 km/year in heavily suburbanized areas of Southern California (Garcia & Muchlinski, 2017 ).…”

Section: Introductionmentioning

confidence: 99%

Timescale analyses of fluctuations in coexisting populations of a native and invasive tree squirrel

Desharnais

Muchlinski

Ortiz

et al. 2022

Ecology and Evolution

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Competition from invasive species is an increasing threat to biodiversity. In Southern California, the western gray squirrel ( Sciurus griseus , WGS) is facing competition from the fox squirrel ( Sciurus niger , FS), an invasive congener. We used spectral methods to analyze 140 consecutive monthly censuses of WGS and FS within a 11.3 ha section of the California Botanic Garden. Variation in the numbers for both species and their synchrony was distributed across long timescales (>15 months). After filtering out annual changes, concurrent mean monthly temperatures from nearby Ontario Airport yielded a spectrum with a large semi‐annual peak and significant spectral power at long timescales (>28 months). The cospectrum between WGS numbers and temperature revealed a significant negative correlation at long timescales (>35 months). Cospectra also revealed significant negative correlations with temperature at a six‐month timescale for both WGS and FS. Simulations from a model of two competing species indicate that the risk of extinction for the weaker competitor increases quickly as environmental noise shifts from short to long timescales. We analyzed the timescales of fluctuations in detrended mean annual temperatures for the time period 1915–2014 from 1218 locations across the continental USA. In the last two decades, significant shifts from short to long timescales have occurred, from <3 years to 4–6 years. Our results indicate that (i) population fluctuations in co‐occurring native and invasive tree squirrels are synchronous, occur over long timescales, and may be driven by fluctuations in environmental conditions; (ii) long timescale population fluctuations increase the risk of extinction in competing species, especially for the inferior competitor; and (iii) the timescales of interannual environmental fluctuations may be increasing from recent historical values. These results have broad implications for the impact of climate change on the maintenance of biodiversity.

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Distribution of the Eastern Fox Squirrel (Sciurus niger) in Southern California

Cited by 12 publications

References 14 publications

Eastern fox squirrel (Sciurus niger, Linnaeus 1758) introduction to the Sonoran Desert

Eastern fox squirrel (Sciurus niger, Linnaeus 1758) introduction to the Sonoran Desert

Eastern Fox Squirrels and Western Gray Squirrels in Southern California

Timescale analyses of fluctuations in coexisting populations of a native and invasive tree squirrel

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