Red squirrels are found in a range of habitats, from conifer forests to broadleaf woodland, including urban parks and gardens. They can live in mountainous areas up to the tree line, and have been seen at altitudes of 425m near Aberdeen.
Although restricted to woodlands, their use of individual woods depends heavily on the availability oft tree seeds and other food types. They are most abundant in woodlands of Scots pine or of mixed conifers, where they live at average densities of around one squirrel per hectare (2.5 acres). However, they can also survive well in broad leaf woodland, especially those with plentiful hazel nuts, where their population densities are similar to those found in pure conifer woodland.
Although grey squirrels have replaced red squirrels across much of England and Wales (and continue to encroach on the range of red squirrels in Scotland), there are some areas in Scotland where the two species have apparently co-existed for periods in excess of 30 years. This has been attributed to the types of habitat occurring locally, which have sufficient area of conifers to enable red squirrels to survive alongside a grey squirrel population. However, it is not known if this pattern will persist indefinitely.
Grey squirrels by contrast are broadleaf specialists, originating from the oak and hickory forest of eastern North America. They live at much higher densities than red squirrels in these types of woodland with, on average, two to three, but sometimes up to nine, squirrels per hectare. Grey squirrels are able to digest broadleaf seeds, such as acorns, more efficiently than red squirrels, which is thought to be the main reason why they dominate in these areas. However, disease, and habitat loss and fragmentation, may contribute to making areas less suitable for red squirrels to survive.
