COMPARATIVE DEMOGRAPHY OF RED SQUIRRELS (SCIURUS-VULGARIS) AND GREY SQUIRRELS (SCIURUS-CAROLINENSIS) IN DECIDUOUS AND CONIFER WOODLAND

The demography of red and grey squirrels was studied by live-trapping and radio-tagging at 14 deciduous and conifer sites in southern Britai n and at eight conifer sites for one year in northern England. Densiti es and productivity correlated with tree seed crops for both squirrel species in deciduous and conifer habitats. Productivity was reduced by high density of full-grown squirrels relative to seed abundance. In o ak-hazel woods, demography of grey squirrels correlated with abundance of acorns but not of hazel-nuts, whereas density and productivity of red squirrels correlated with hazel-nut abundance. Correlations of fem ale density and productivity with pine-cone crops did not differ betwe en red and grey squirrels, Predators ate many radio-tagged grey squirr els in conifers, and annual survival was only 50% compared with 80-82% for both species in other habitats. Grey squirrel populations in sout hern conifer sites were sustained by immigration, and at northern site s female density correlated with oak abundance within 500 m. Failure t o exploit acorn crops puts red squirrels at a competitive disadvantage in deciduous woodland. Red squirrels had higher survival than grey sq uirrels in conifers, which may give them an advantage in that habitat, but could also have been explained by a lack of predators on their is land study site.