National monitoring of the flying squirrel

The Siberian flying squirrel is a well-known inhabitant of old forests that stirs up emotions and hence often features in the news. Did you know that trends in Finnish flying squirrel populations are monitored almost on a yearly basis? Such national monitoring produces data for the assessment and conservation of this threatened species, among other things.
Monitoring data spanning almost 20 years

In Finland, flying squirrels have been monitored using the same method since 2003. Originally, over 10,000 square-shaped surveying areas, nine hectares in size, were randomly selected from different parts of Finland, and signs of flying squirrels were collected from these areas between 2003 and 2005. 

Since then, some 1,680 such areas have been selected for continuous monitoring. These survey patches are divided over 13 monitoring areas and cover the distribution range of the flying squirrel from the southern parts of the country to the outskirts of the Kainuu region in the north.

When, where and how?

The monitoring of the flying squirrel is financed by the Ministry of the Environment and coordinated by the Finnish Museum of Natural History. The best time for surveys is from early spring to early summer, when hired surveyors search for yellowish droppings under aspens and sturdier spruces.

Looking for droppings is a painstaking effort, and it can easily take an hour and a half to go through one square-shaped surveying area full of spruces and aspens. The surveying of the area is immediately stopped at the sighting of the first dropping, and the search moves on to the next surveying area in the vicinity.

Data to support conservation and research

The surveying helps in assessing the annual fluctuations of flying squirrel populations in the different monitoring areas. However, the surveying results do not translate into accurate estimates of population sizes.

Approximately one-third of the forest areas under continuous monitoring have gone through management processes such as final felling, which have rendered these areas unsuitable for flying squirrels, and some of the areas contain only small patches of suitable forest.

The trend and scale of change indicated by the monitoring is used in determining the threat level for the species. In 2019 the Finnish flying squirrel population was classified as endangered.

The data accumulated in flying squirrel monitoring have been used in a number of scientific studies. When data on the distribution of flying squirrels are combined with, for example, data on forest resources, information on the best habitats for the species becomes available, and further research can be conducted to determine what kind of forest the species requires to make a specific area their home.