Effects of temporal and spatial variations in food supply on the space and habitat use of red squirrels (Sciurus vulgaris L.)

Abstract

In non-native conifer plantations characterized by strong spatial and temporal variations in the availability of tree seeds in Spadeadam Forest, northern England, the home range and habitat use of red squirrels Sciurus vulgaris was very¯exible. Males tended to have much larger home ranges than females and coreareas of most breeding females seemed mutually exclusive. Adult female red squirrels were found to increase their home range and core-area size in forest patches where food was less abundant. Home-range size was signi®cantly related to home-range quality and the extent of overlap by other females. In contrast with high-quality continuous conifer forests: (1) a considerable proportion of adult males and females at Spadeadam shifted home range, (2) both sexes had much larger home ranges than reported from other habitats in Britain or Belgium. Many ranges were multinuclear, particularly from January onwards, when supplies of seeds become depleted through consumption and seed shed. Squirrels tracked the availability of conifer seeds (lodgepole pine cones throughout the study, Norway spruce cones in spring 1992 and Sitka spruce cones in autumn 1993) and intensively used several non-adjacent activity centres in temporally food-rich patches. Consequently, habitat preference changed markedly with time. The squirrels seemed to maximize nitrogen intake and to avoid the smaller seeds when possible. This resulted in an overall preference for a mixed diet of lodgepole pine and spruce seeds and avoidance of Sitka spruce seeds when Norway spruce seeds were available. These results lend support to the hypothesis of Ostfeld (1985) that when food is sparse and patchily distributed, females should develop intrasexual territoriality, concentrating their activity in food-rich patches, while males should be non-territorial and adapt their space use to the distribution of females.

Female home range size is regulated by resource distribution and intraspecific competition: a long-term field study

“…Several previous correlative studies have supported the idea that home ranges function to provide sufficient food resources (Tufto et al 1996;Lurz et al 2000;Saïd et al 2005) and this has been shown experimentally in bank voles, Clethrionomys glareolus (Jonsson et al 2002). In agreement with this, in our study, smaller home ranges contained a greater percentage of food plants and especially a greater relative abundance of annuals.…”

“…Intraspecifically, home range size differs seasonally (Lovallo & Anderson 1996;Bixler & Gittleman 2000;Lurz et al 2000;Kjellander et al 2004;Do Linh San et al 2007; but see Rodrigues & Monteiro-Filho 2000 for no effect). Explanations for the seasonal variation in home range size include seasonal changes in reproductive activity, population density or food availability.…”

“…Explanations for the seasonal variation in home range size include seasonal changes in reproductive activity, population density or food availability. In fact, several correlative studies on different species indicate that home range size decreases with increasing food availability (Tufto et al 1996;Lurz et al 2000;Saïd et al 2005;Rö del & Stubbe 2006). Furthermore, experimental provisioning of supplemental food resulted in decreases in home range size (Taitt 1981;Taitt & Krebs 1981;Ims 1987;Boutin 1990;Hubbs & Boonstra 1998;Jonsson et al 2002;but see Broughton & Dickman 1991).…”

Habitat use and population density of the red squirrel, Sciurus vulgaris meridionalis, in the Sila Grande mountain range (Calabria, South Italy)

“…Möller, 1983;Gurnell, 1987;. Consequently, annual fluctuations in tree seed crops and spatial variation in tree seed abundance are the main determinants of red squirrel population dynamics, in particular reproductive rate and dispersal behaviour (Wauters & Dhondt, 1990;Wauters & Lens 1995;Lurz et al, 1997), spacing behaviour and habitat use Piqué, 1997;Lurz et al, 1999). Red squirrel densities vary widely throughout their European range (reviewed in Lurz et al, 1995): they are lowest in young boreal forests and man-made conifer plantations in northern England, intermediate in mixed broadleaf-pine forests in southern Europe and in oak-hazel woodlands in England, and highest in Scots pine dominated woodlands and mixed oak-beech-Scots pine woodlands in western-Europe (Lurz et al, 1995;Wauters & Lens, 1995;Piqué, 1997;Kenward et al, 1998;Wauters & Gurnell, 1999).…”

The use of species‐specific cone remains of sympatric arboreal rodents to monitor their distribution

“…In areas where conifers are common, cone line feeding transects have been used to study squirrels in Britain, Belgium and Italy (Moller 1986;Wauters & Dhondt 1987Wauters & Lens 1995;Lurz et al 1998Lurz et al , 2000Gurnell et al 2004;Wauters et al 2004). In areas where both red and grey squirrels occur, this technique does not allow differentiation between the two species since the two congeners leave similar-shaped stripped cones after feeding on the seeds (Gurnell et al 2004).…”