Spatial dynamics of fox squirrels (Sciurus niger) in fragmented landscapes

Abstract

We examined the spatial dynamics of fox squirrels (Sciurus niger) occupying 12 woodland sites in a predominantly agricultural landscape of west-central Indiana. The 12 sites represented woodlands of varying degrees of isolation and size. Forty-nine adult fox squirrels were fitted with radio collars and monitored from May 1993 through September 1994. No movements of collared adults were observed between wooded sites during the study, although squirrels traveled 200-500 m from woodlots along hedgerows, and 2.6% of observations occurred in agricultural fields. Multiple regression revealed a positive linear relationship between home-range size and woodland size, with larger home ranges in the growing season. Home-range size was not related to woodland isolation, squirrel density, or sex. We found no evidence of spatial interactions between pairs of squirrels (i.e., male-male, male-female, female-female) at resolutions of 20, 40, or 100 m. Excursions beyond a core area were of relatively greater magnitude for squirrels occupying continuous forest. Agriculturally induced fragmentation of forests appears to restrict movements of adult fox squirrels, despite the well-documented ability of the species to persist in such a landscape.

The response of tree squirrels to fragmentation: a review and synthesis

“…Home Robinson & McCowan, 1954;Flyger, 1960;Cordes, 1965;Taylor, 1966;Geeslin, 1970;Cordes & Barkalow, 1972;Silva, 1972;Erossy, 1973;Doebel & McGinnes, 1974;McCloskey, 1975;Adams, 1976;Benson, 1980;Wauters & Dhondt, 1985Weigl et al, 1989;Kantola & Humphrey, 1990;Andren & Delin, 1994;Wauters et al, 1994aWauters et al, , 2001Sheperd & Swihart, 1995;Shuttleworth, 1996;Halliwell, 1997;Münch, 1998;Smith, 1999;Cartmel, 2000;Conner, 2000;Nupp & Swihart, 2000. ranges of fox squirrels (Baumgartner, 1943) and eastern grey squirrels (Erossy, 1973) were suggested to be positively related to woodlot size. Empirical support for this was found in fragmented forests in agricultural regions of Indiana (Sheperd & Swihart, 1995). Densities were also noted to be higher in fragmented landscapes relative to continuous forests for red squirrels (Bayne & Hobson, 2000) and eastern grey squirrels (Fisher & Merriam, 2000).…”

“…Consequences of fragmentation for abiotic and biotic components of ecosystems are varied (for reviews, see Yahner, 1988;Tscharntke et al, 2002). Most major ecosystems have been fragmented through anthropogenic activities in the last 200 years; however, forested ecosystems have undergone excessively high levels of fragmentation (Nixon, Havera & Hansen, 1978;Middleton & Merriam, 1983;Harris, 1984;Nixon & Hansen, 1987;Sheperd & Swihart, 1995;Verbeylen, De Bruyn & Matthysen, 2003). Genetic variation is often, but not always, lost with habitat fragmentation (Avise, Neigel & Arnold, 1984;Wauters et al, 1994b;Frankham, 1997;Eldridge et al, 1999;Small, Stone & Cook, 2003).…”

“…Assessing the impacts of forest fragmentation on this group is thus quite timely. Previous studies of individual species in a local area have suggested that home-range size or density may be related to woodlot size (fox squirrels, Sciurus niger: Baumgartner, 1943;Sheperd & Swihart, 1995; eastern grey squirrels, S. carolinensis : Erossy, 1973;Don, 1983;Fisher & Merriam, 2000; red squirrels, Tamiasciurus hudsonicus: Bayne & Hobson, 2000). Herein, a comparative generalised individuals-area relationship (Gaston & Matter, 2002) approach will be used across species and geographical areas to assess the response of tree squirrel density and home-range size to forest fragmentation.…”

Effects of Habitat Destruction and Resource Supplementation in a Predator–Prey Metapopulation Model

“…Changes in the composition and physiognomy of a landscape resulting from habitat loss and fragmentation (Dunning et al, 1992) can alter genetic structure (Gaines et al, 1997), individual behavior (Lima & Zollner, 1996;Sheperd & Swihart, 1995), local population dynamics (Nupp & Swihart, 1996, 1998, interspeci"c interactions (Keyser et al, 1998), and community composition (Dunstan & Fox, 1996;Hecnar & M'Closkey, 1997;Kolozsvary & Swihart, 1999). Not surprisingly, habitat destruction has been implicated as the major threat to biological diversity (Wilcox & Murphy, 1985).…”

Distribution Patterns of Sciurus niger (Eastern Fox Squirrel) Leaf Nests Within Woodlots Across a Suburban/Urban Landscape

“…Further, the degree of isolation of woodlots across agricultural landscapes in west-central Indiana and east-central Illinois appeared to have little effect on fox squirrel distributions (Goheen et al 2003, Nupp and Swihart 2000, Rosenblatt et al 1999, Swihart and Nupp 1998. The movements of Eastern Fox Squirrels between woodlots isolated by agricultural fi elds in west-central Indiana were, however, restricted to hedgerows, and movement across the open agricultural matrix was rare (Sheperd and Swihart 1995).…”