The effects of seed availability on habitat use by a specialist seed predator
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Space-use patterns of seed predators are strongly affected by spatiotemporal variation in the abundance of different tree seeds, their major food source. However, most studies have measured relationships between overall food availability and space use, and there are few cases where effects of different food resources have been explored. We studied the effects of two food resources, Norway spruce and silver fir seeds, on space and habitat use in red squirrel in a subalpine conifer forest from 2000 to 2006. Fir seeds disperse in the autumn of the year they are produced, spruce the following spring. We estimated spruce and fir seed availability within individual home ranges and monitored home-range size using radiotelemetry. Males had larger home ranges than females and the sexes responded differently to variation in food and density. Spruce seed availability negatively affected home-range and core-area sizes of males in spring–summer. Space use was not affected by fir seed availability. Squirrels positively selected spruce for foraging and spruce was always preferred over fir. Our results showed that spruce, but not fir, affected space and habitat use of squirrels, suggesting they do not behaviourally respond to early seed dispersal in fir.
KeywordsEurasian red squirrel Sciurus vulgaris Norway spruce Silver fir Home-range size
We thank Massimiliano Zaninetti and Giuseppe Airoldi for their help with the fieldwork. Constructive criticism by two anonymous reviewers helped to improve the manuscript. This study is part of the Alpine Squirrel Population Ecology Research (ASPER) project, funded by the province of Sondrio (Servizio Agricoltura, Caccia e Pesca, Settore Risorse Ambientali), the Gran Paradiso National Park, the Stelvio National Park, and the Parco Regionale delle Orobie Valtellinesi to Istituto Oikos NGO, Milan. Additional financial support was given by Ministero dell’Istruzione, dell’Università della Ricerca (MIUR, project COFIN 2003, number 2003053710-006) to Insubria University of Varese. Trapping and handling squirrels complied with the current laws on animal research in Italy and were carried out under permission of the Region of Lombardy. This is paper #21 of the ASPER project.
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