The quarterly of the University of Helsinki

Tapio Ollikainen

Back to spring issue 2003

It was a light summer's night in my childhood, when my brother and I were sitting under a spruce outside the house. Suddenly, somethingswished over me so that the breeze tousled my hair. It was a flying squirrel,” tells ecologist Vesa Selonen about his first encounter with the furry glider.

The boys told their neighbour, the well-known Finnish nature photographer Heikki Willamo about it and he, in turn, informed the university. Before long, a student working on his MA thesis was criss-crossing the area around the boys' summerhouse in Kisko, in western Finland, measuring the distances between trees and scribbling something in his notebook. In Selonen's eyes, it all looked a little strange and funny. “I would never have thought that one day I would be doing the same kind of work,” he laughs.

In November 2002, Selonen defended his doctoral dissertation, Spacing behaviour of the Siberian flying squirrel – effects of landscape structure, at the Department of Ecology and Systematics, University of Helsinki.

Hobby becomes work

The couple of decades between the first encounter and the doctorate passed with nature as a hobby. In his childhood, fishing trips, made together with his grandfather, were very important for Selonen. After that, birding took his fancy. During upper secondary school, nature conservation attracted him and, finally, what had been a hobby turned into work as an ecologist.

“I am interested not just in the flying squirrel as such but also in the central question of ecology, namely, what affects the size of a population and its survival in the world as the whole. Nevertheless, the flying squirrel is not a bad research object: it is an ecologically interesting species about which we know little. And it is also a slightly mysterious or even mystified creature.”

Even after his dissertation, Selonen intends to continue working with the flying squirrel. He is just applying for funding for a project using mathematical models for calculating the survival chances of the flying squirrel population in the Finnish forests. Furthermore, the intention is to establish the number of flying squirrels in Finland. This is much needed information, as the current estimates vary from 10,000 to 100,000 pairs.

Selonen's significant other is a biologist, so they rarely disagree on how or where to spend their holidays: anywhere is good enough, as long as you can hike about observing birds and looking at moss and plants. But is that really a holiday if you have 'work' in front of your nose all the time?

“Research is much about writing, while nature is such a complex system that you never get bored with it. I have been on holiday in New York and London as well and liked it,” says Selonen.

Fascination and friction

The flying squirrel is akin to the common squirrel. The Siberian flying squirrel eats buds and leaves and lives in the trees, while its American cousin also lives on the ground and eats truffles, for example. There are several flying species in South America. A subspecies of the Siberian flying squirrel is found in Japan, and flying phalangers live in Australia.

And here is the most interesting fact: the flying squirrel can glide over a distance of up to 70 metres. This little nocturnal mammal may travel several kilometres a night. “For instance, when young flying squirrels become independent, they may move up to nine kilometres from the mother squirrel's territory which is rare among mammals of this size. Research has shown that the territory of a male flying squirrel may even cover 60 hectares and that of a female nine hectares.”

How do you observe such a 'fly about'?

“First, we located the nesting hole of the flying squirrels. Then we fastened a deep bucket in front of it, into which the squirrel fell at dusk and could not crawl out of. Then we simply put a radio transmitter around its neck and followed the signal.”

The hole may be so high up in a tree that you need climbing irons. “My supervisor, university lecturer Ilpo K. Hanski took care of climbing the trees, for which I am extremely grateful,” Selonen laughs.

Apart from being met with fascination, the flying squirrels raise heated discussions in Finland when economy and ecology are butting heads. Forest owners do not want to lose their right to cut their forests, while according to the EU Habitats Directive it is forbidden to destroy or impair the breeding and resting places of the flying squirrel.

The Finnish environmental authorities are trying to find an amicable solution which would not include grave economic losses for the forest owners. Research to date, however, cannot define precisely how much forestland ought to be conserved in order to preserve the species. “Actually, a major problem today is that there are not enough suitable habitats in Finland for the flying squirrel to move into.”

Vesa Selonen: Spacing behaviour of the Siberian flying squirrel – effects of landscape structure. 126 pages. Oy Edita, Helsinki 2002. ISBN 952-91-5125-x. http://ethesis.helsinki.fi 952-10-0725-7 (pdf) §