Studies on red squirrels in the Italian Alps

Luc Wauters, Heidi Hauffe, Guido Tosi and Sandro Bertolino

The Eurasian red squirrel has become extinct or very rare in those parts of its distribution range invaded by the introduced Eastern grey squirrel (Sciurus carolinensis), which, in northern Italy, has reached the Prealpine forests. Red squirrels are still found throughout the extensive alpine conifer forests. Models based on spatial distribution and population dynamics suggest that red squirrels might persist in large tracts of conifer forest, and that alpine populations might constitute a stronghold against spreading grey squirrels. Although natural alpine conifer forests are likely to present the major area in northern Italy and Central Europe where red squirrels can survive on the long-term, no data exist on squirrel demography, social organisation and habitat use in these habitats. Therefore, this project aims to study: annual variation in conifer seed production, as primary food resource; population size and habitat preference using hair-tube surveys; annual variation in population densities and the underlying demographic processes; and habitat use and spacing behaviour in different forest types.

The main objectives of the study are:

  1. Monitoring annual variation in conifer seed production of larch and spruce, as a measure of food availability for red squirrels, and the rate of seed consumption by squirrels and other seed predators;
  2. Monitoring population size and habitat preference using hair-tube surveys;
  3. Critical analysis of the use of hair-tubes to develop a reliable population density index;
  4. Studying annual variation in squirrel density and of the demographic processes (survival, reproduction, dispersal) using capture-mark-recapture and radio-telemetry;
  5. Studying habitat use and spacing behaviour (home range size, home range use and core-area overlap) in relation to (seasonal changes in) food availability in the different forest types.

Actually red squirrels are being studied in six study sites that differ in forest composition and elevation:

Study site Habitat type Elevation
(m a.s.l.)
Sondrio, Cedrasco mixed silver fir (Abies alba, 58%), Norway spruce (Picea abies, 23%), other conifers (7%), beech and chestnut (12%) 1200 – 1600 1999 – 2001
Sondrio, Oga Scots pine (Pinus sylvestris 83%), with some Norway spruce (10%) and larch (7%) 1300 – 1450 1999 – 2001
San Antonio mixed Norway spuce (85%), few larch (Larix decidua, 7%), dead trees (8%) 1600 – 1750 2000 – 2002
Valtellina, Bormio Swiss stone pine (Pinus cembra) 1900 – 2000 2000 – 2002
Gran Paradiso NP, Cogne mixed larch (54%), Norway spruce (46%) 1590 – 1710 2000 – 2002
Gran Paradiso NP, Rhemes mixed Norway spruce (85%), larch (15%) 1700 – 1800 2000 – 2002

These studies are funded by different local bodies: The Province of Sondrio, Hunting and Fishing Service; The Region of Lombardy, “Project Multifunctional Use of Forests”; and the Gran Paradiso National Park. Several scientific institutes and NGO’s are collaborating, and take part at the fieldwork in a subset of study sites: Department of Structural and Functional Biology, University of Insubria, Varese (Italy); Oikos Institute, Varese (Italy); FaunaViva, Rho (Italy); Department of Entomology and Applied Zoology, University of Turin (Italy); Department of Biology, UIA, University of Antwerp (Belgium).

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