Project title:	Genetic variation in the red squirrel
Collaborators:	Dr Kirsten Wolff & Dr Marie Hale
Funding:	FABS & AES

Background

The red squirrel (Sciurus vulgaris) is the only squirrel species native to the UK. However, its range has been declining and it is now largely absent from south and central England, most of Wales and parts of Scotland (Gurnell 1987). This decline in red squirrels has been matched by an increase in the population of the introduced North American grey squirrel probably because the grey squirrels are better than the red squirrels at exploiting areas of mixed woodlands (Kenward & Holm 1993). This advance of the grey squirrel is gradually confining the red squirrels to the large spruce dominated conifers plantations in the north of England and to small, isolated fragments of woodlands.

Problem

With the physical isolation of populations comes the possibility of genetic isolation. The loss of genetic variability in isolated populations of red squirrels, as may be found in these forest fragments, will ultimately reduce their overall chance of survival. This potential isolation may be reduced in the red squirrel due to dispersal periods. During these phases, there may be communication between forest fragments and with the main genetic pool. This interaction will depend on the distance between forest fragments and the presence of viable corridors (e.g. hedgerows) between them. In other populations of red squirrels, the density is much higher in forest fragments than in continuous woodlands suggesting that fewer animals leave an area. In addition, females living in good territories are unlikely to move (Wauters, Lens & Dhondt 1995), which will also increase the genetic isolation of an area.

Solution

DNA techniques are useful tools for determining genetic variation and population structure in many threatened and/or endangered species. For example, RAPDS have been used to get a rough idea of population structure. Sequencing of stretches of mtDNA has shown patterns of gene transfer between populations, whereas microsatellites have been extremely informative in determining parentage. These techniques are currently being used to investigate the genetic structure of the red and grey squirrel.