Demographic characteristics of an unexploited population of fox squirrels (<i>Sciurus niger</i>)

Nixon, Charles M.; Hansen, Lonnie P.; Havera, Stephen P.

doi:10.1139/z86-076

Cited by 7 publications

(4 citation statements)

References 34 publications

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“…In temperate, mixed deciduous forests, densities of eastern grey squirrels ( Sciurus carolinensis Gmelin) and fox squirrels ( Sciurus niger L.) remain relatively stable, or fluctuate annually, and are positively correlated with the size of the previous year's seed (acorn) crop (e.g. Thompson 1978; Nixon, Hansen & Havera 1986; Gurnell 1996).…”

Section: Discussionmentioning

confidence: 99%

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Within‐sex density dependence and population dynamics of red squirrels Sciurus vulgaris

Wauters

Matthysen

Adriaensen

et al. 2004

Journal of Animal Ecology

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Summary1. Social organization and dispersal of red squirrels ( Sciurus vulgaris L.) differ between sexes, and intrasexual competition is intense. Therefore, we predicted that demographic parameters should be gender-specific: that is density-dependent factors will be more strongly related to density of the same sex than to density of the opposite sex. We studied the relative importance of within-and between-sex density-dependent factors and of density-independent factors (habitat type, food abundance, winter temperature) on different demographic parameters, in two populations in northern Belgium. 2. Spring density of males was positively correlated with tree-seed abundance in the previous year, but this was not the case for females. None of the population parameters we measured differed between habitats, indicating that the same density-dependent and density-independent mechanisms prevailed in coniferous and deciduous habitat. 3. Within each sex, we found several demographic parameters that were dependent on the densities of the same sex; however, none of these parameters was found to be dependent on the density of the opposite sex. 4. Reproductive rate increased with food abundance and decreased with female density. Adult survival of females decreased with female density in autumn-winter, while survival of adult males in spring-summer increased with the size of the previous year's seed crop. 5. Immigration rate of males was higher in spring than in autumn, and spring immigration increased with food abundance. Male recruitment rate, in both seasons, increased with food abundance, but was male density dependent. However, springsummer loss rates also increased when food supplies were good, suggesting that despite high food availability, emigration of juvenile and subadult males increased when intrasexual competition was intense. Recruitment rate of females decreased with increasing female density. After a good seed crop, more subadult females dispersed, but their settlement success (recruitment) was lower at high female density. 6. Seed crop size positively affected red squirrel densities through increased reproduction, immigration and adult survival of males, but density-dependent reproduction and withinsex density-dependent recruitment of locally born juveniles and dispersing subadults limit the fluctuations in numbers and regulate densities in winter-early spring, as well as in summer.

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Section: Discussionmentioning

confidence: 99%

“…1993). Similarly, the behaviour of resident adult grey squirrels seemed to regulate recruitment, and in turn population density, through interactions with juveniles and subadults (Thompson 1978), while in fox squirrels, recruitment of young improved when female density was reduced (Hansen & Nixon 1985; Nixon et al . 1986).…”

Section: Discussionmentioning

confidence: 99%

Within‐sex density dependence and population dynamics of red squirrels Sciurus vulgaris

Wauters

Matthysen

Adriaensen

et al. 2004

Journal of Animal Ecology

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“…We cannot rule out large-scale movements by 3 squirrels whose fates were unknown, but the intensity of our monitoring and searching programs led us to conclude that such movements were unlikely to have occurred. Although adult squirrels are capable of moving > 1 krn on occasion (Baumgartner 1943;Adams 1976), most dispersal involves juveniles and subadults (Nixon et al 1974(Nixon et al , 1986Delong 1986). Adams (1976) found that subadults exhibited the largest home ranges, and he attributed this to investigative behavior, possibly in preparation for dispersal.…”

Section: Long-range Movements From and Between Woodlotsmentioning

confidence: 99%

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

Sheperd¹,

Swihart²

1995

Can. J. Zool.

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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.

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“…Although adult eastern fox squirrels are capable of moving .1 km (Shepherd and Swihart, 1995), most dispersal involves juveniles and subadults (Nixon et al, 1974(Nixon et al, , 1986Koprowski, 1996) during April-May or July-October (Thompson, 1978). These movements twice a year may greatly contribute to expansion of range in southern California.…”

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confidence: 99%