The Flying squirrel is Espoo's official town animal and the symbol of the Nuuksio National Park. Flying squirrels are especially abundant in the northern part of the city, but in recent years there have also been several sightings in the densely built areas in the south. A study conducted in 2013 sought to probe the geographic range of the Flying squirrel in Southern Espoo, the extent thereof, and the routes the squirrels use. To this end, some of the squirrels where fitted with radio tracking collars for monitoring their movements.
According to the data accumulated over the past decade, flying squirrels populate at least the central park and Soukanniemi area south of the train tracks. Other areas with sightings in the last a couple of years include Espoo Centre, Tapiola, Laajalahti, Hannusmetsä and Kaitaa south of Länsiväylä, and Matinkylä.
Often the presence of a flying squirrel is detected from mustard-coloured, rice grain size droppings found under spruces or aspens. The best times to spot droppings are in late winter, post-thaw spring and early summer before they are covered by vegetation. In summer, the droppings are brown and very difficult to detect.
Importance of spruces and deciduous trees
Flying squirrels like mature mixed forests with big spruces and tall aspens and other deciduous trees. They also favour herb-rich areas below cliffs, and thick forests next to fields, lakes and streams. Pine heaths are not good habitats, but flying squirrels do not mind lush hollows in rocky pine stands, provided that there is a crown contact with suitable feeding and nesting areas nearby. Small groups of trees inside clear-cut areas or sampling stands are too small for breeding, although they would otherwise make suitable habitats.
The Flying squirrel is clumsy on the ground and avoids going there. Even a narrow forest strip or individual trees here and there create a sufficient enough corridor between the nest and several smaller feeding areas. The trees should stand at least 20-30 metres apart and be high enough for smooth gliding.
Nocturnal hole nester
Flying squirrels prefer building a spherical nest inside a woodpecker hole in an aspen, but do not shy away from old squirrel's nests or even nest boxes. Flying squirrels sleep the days in their nests, but at night they become active. Only the nursing females eat during the day.
Average litter size is two or three, and some females give birth both in the spring and the summer. The young leave the nest after mid-July and disperse in search of their own living place. This phase is very risky and the death rate high. Flying squirrels may reach a maximum age of 5 years, but only a few live that long. The squirrels are hunted by hawks, owls and martens, and, therefore, they need the protection of trees.
Females are highly territorial
The Flying squirrel female lives her entire life in the same area where she wandered during her first autumn. The habitat and nesting hole should be sufficient enough for a young female to spend her winter, stay healthy and raise her young the following year. The average territory is four hectares in size and its core area a little over a hectare.
The core may be smaller if there are good crown contacts to other feeding areas in the vicinity. During breeding period, the female does not tolerate other females inside her territory. A male territory is usually tens of hectares in size. The territories may overlap and contain one or more female territories.
The Flying squirrel is an herbivore. In spring and summer, it feeds on alder, aspen, birch and rowan buds and leaves, conifer buds and blooms, and green spruce cones, and in late summer also on birch seeds and rowan berries. Their winter diet consists of pine buds and birch and alder catkins, which the squirrel stores in large quantities on birch branches and other caches.
Population in steep decline
The Flying squirrel is classified as a vulnerable species in Finland. The population has been in steep decline for decades mostly due to the logging of mature mixed spruce forests. Planted pine stands do not make suitable habitats over an entire tree generation, nor forests with deciduous trees cleared away.
The Nature Conservation Decree prohibits the deterioration and destruction of breeding sites and resting places of the Flying squirrel. Its nesting and feeding trees may not be chopped down, or its travel routes disrupted by tree felling, for example.
Flying squirrel is Finland's priority species in the EU
Although the flying squirrel distribution extends in the east throughout Siberia, close to the eastern border of Finland the population is sparse. Should the population in Finland deteriorate, we cannot count on the east for replenishments. In addition to Finland, the only EU country with flying squirrels is Estonia, but the population is limited there to just a few hundred animals. In Latvia and Lithuania, it has become extinct. Flying squirrel is Finland's priority species in the EU. Finland has a duty to research and monitor the species, and to consider its natural habitats in land use planning.
In Espoo, this means preserving flying squirrel's habitats and travel routes despite the growing population, the expanding and ever denser urban structures, and the new developments concentrated around metro stations. Radio tracking collars are hoped to provide enough information to this end. And when the Flying squirrel is taken into account in city planning and environmental conservation, other parts of nature also get preserved.