Management of woodland habitat to favour red squirrel conservation

With the population of red squirrels in Ireland in decline, this section examines how we can manage our woodland habitat to favour red squirrel conservation.

Selecting the tree species that favour red squirrels but are unlikely to encourage grey squirrels into the core area is of paramount importance. Favourable species include Scots pine, larch, Norway spruce, lodgepole pine, Douglas fir, yew and hawthorn. Even a commercial plantation consisting primarily of the North American conifer Sitka spruce, can contribute to red squirrel conservation, providing that 20% of the tree cover consists of the above favoured species , where suitable site conditions prevail.

It should be emphasised that healthy seed producing crowns will only result where tree species are matched to site conditions and the trees themselves reach a minimum of 30 years of age. Sitka spruce itself has a neutral value - it neither encourages grey squirrel incursions, nor does it encourage red squirrels into the area.

Table 1 Commonly planted tree species that benefit red squirrel conservation (Forestry Commission Bulletin 14)

Oak, beech, chestnut and hazel are large seeded deciduous trees, which favour grey squirrel incursions and should not be planted within red squirrel conservation areas:. It may be appropriate to fell individual trees of these species, if they bear large quantities of seed, and encourage grey squirrel incursions into the core area.

The favoured tree species may be planted in mixture, which can reduce the impact of poor cone years of a particular species. Crown development resulting in improved seed production, can be encouraged by concentrating these species around the edges of rides or roadsides.

Woodland managers who require broadleaves for landscape or biodiversity reasons should use any of the following species - birch, rowan, ash, willow, aspen or alder. These species produce small seed and although they are not a favoured food source for the red squirrel, they do not encourage grey squirrel incursions.

The existence of berry bearing shrubs consisting of hawthorn, dog rose and guelder rose will provide additional food sources for the red squirrel.

Expanding areas of new forest and woodland of the appropriate tree species within the core areas will increase the viability of red squirrel populations.

A range of age classes should occur throughout the forest so that seed bearing trees exist at all times, thereby providing a continual supply of food for the red squirrel. An ideal wooded area will consist of tree cover within the following age classes in roughly equal proportions: 0-15 years, 15-30 years, and 30+ years.

The removal of weaker stems to promote larger crowns in the remaining crop is likely to increase the quantity of viable seed. This in effect will result in additional food for the red squirrel.

If continuous cover can be maintained on a site, through the development of an understorey, a continuous source of food is available to the red squirrel. It is also possible that a dense understorey may impede the movement of the grey squirrel, because it spends much of its time foraging for food on the ground, in contrast to the red squirrel which spends much of its time in the canopy.

Where clearfelling is necessary, a reduction in the size of the clearfell may be beneficial in order to avoid fragmentation of the red squirrel habitat. Large clearfells can restrict movement of the red squirrel through the forest, since it moves primarily from tree crown to tree crown, and dislikes travelling across open areas for fear of predation. Clearfelling a favoured tree species is also likely to interrupt the red squirrel's food supply.

Retaining areas consisting of those species upon which the red squirrel is most dependant beyond their normal "economic" age will provide a valuable food source for a longer period of time. This is especially important for holding existing red squirrel populations in areas where the favourable species are present, but have not reached a maturity where large quantities of seed are produced.

Harvesting operations in the spring can adversely affect unweaned young, and such operations should where possible, be avoided during this period. The breeding season can start as early as January, females usually have one litter comprising of an average of 3 young per year. One in ten female red squirrels can breed twice, the second litter being born between May and September.