Suomen Luonto
English summaries 7/2003

The dragonfly or "devil's balance"
By Juha Kauppinen
Pages 4-11

The Carboniferous period was the heyday of dragonflies (Odonata). At that time the largest species had a wingspan of up to 70 cm, whereas the largest modern dragonfly only manages 18 cm. Part of the reason for the insects? enormous wingspan was the oxygen concentration of the atmosphere, which at the time reached 35% compared to its present day level of 21%.

The dragonfly was an extremely successful and adaptable animal pattern. This is borne out by the fact that not only has its basic structure remained relatively unchanged for 300 million years, but this type of insect has survived three major waves of extinction when as many as 77-96% of all species were wiped out. The most spectacular period of extinction ushered out the Permian period and at the same time the Palaeozoic era some 225 million years ago.

There are approximately 5,500 known living species of dragonflies. Many more, however, are still to be discovered and dozens of new species are named every year. A total of 53 species of Odonata out of Europe's 131 occur in Finland.

The life of a dragonfly begins with pairing. Prior to this event, the male flies about close to, or over, water, where it defends its territory and courts females. Females often live far from water, but return there to breed. After copulation, a female will lay in the water or right at the water?s edge.
Nymphs (larvae) hatch from the eggs, to spend 2-6 years in Finland's cold waters! Thus, by far the longest part of a dragonfly's life cycle is the nymph stage. The nymphs are predatory, preying on insects, insect larvae, tadpoles and small fish. Odonata are hemimetabolic, i.e. there is no pupal stage in the life cycle. When the adult has fully formed inside the nymph shell, the nymph climbs up out of the water on to a plant stem or leaf - or quite often up a lakeside sauna or boat house wall. The nymph skin splits at the back and out climbs the dragonfly. The adult remains for a few hours next to its empty nymph skin, flattens out its crumpled wings, and then flies away, leaving the empty skin, which has the appearance of a small though horrific monster, behind.

Many beliefs and legends are associated with dragonflies in various parts of the world. Local names for them indicate how folk feel or have felt about them. In Sweden a dragonfly is known colloquially as a "witch's distaff or spindle", in Danish and Spanish it is the "devil's coach horse" (a name reserved for a staphylinid beetle in Britain!), in Finland the "devil's balance", and in German the "devil's needle". But in Japan, for example, the insect is treated with reverence and is considered a friend of the people. Indeed the old name for Japan was Akitsushima, or Dragonfly Island.

Dragonflies are skilful fliers which grab their prey in mid-flight. This aerial skill is attributable to two pairs of wings that function independently. The insects are of use to mankind because they catch large numbers of mosquitoes and gnats. In addition to a good set of wings, dragonflies also possess outstanding eyesight. In fact the head of a dragonfly appears to consist wholly of its two enormous compound eyes. Thanks to these eyes, the dragonfly has a field of view of almost 360 degrees. As each eye is composed of almost 10,000 omatidia, the insect is able to discern even the slightest movement.

Four of Finland's Odonata species are classed as endangered, all for the same reason: habitats suitable for them have decreased and been downgraded by mankind. It will be interesting to see how these dragonflies survive the latest, currently ongoing wave of extinction caused by the much younger human species.

From chick to adult in a single summer
Text and photos by Heikki Willamo
Pages 16-21

A pair of goshawks has three hungry offspring which cry almost ceaselessly for food. Summer has already entered its second half and the young goshawks have just learned to fly. Two of them are perched on a branch of the nest tree, while the third has flapped its way over to a nearby birch.

Hatching over a month ago, the young hawks are now large and splendid examples of their tribe. The yellowish juvenile plumage has begun to appear from under their original white down covering. Food brought by the parents to their offspring consists of young jays and thrushes, hooded crows from the edge of a field, and hazel hen chicks discovered cheeping plaintively in the grass.

Over a period of several weeks the writer photographed events at the nest and the development of the young birds from a hide. He observed four different pairs of goshawks for several years before deciding that this pair's habits were ideal for monitoring. The male always brought prey to the same places, where it was possible to observe the antics of both the young and their parents. At other nests the young were fed all over the forest once they were capable of flight.

Goshawk parents have a clear division of labour, the larger female guarding the nest and the young birds around it, while the smaller male brings them food as fast and as often as he can. When danger threatens, the mother quietly warns the family, causing the young to cease their commotion, at least for a while. It often happens that young hawks squabble over food brought by the father. During one such dispute an eagle owl arrived and killed one of the young; the victim?s ringed leg was found in the owl?s nest the next year. In August everything comes to an end - only to start up again next spring.

Eastern Gulf of Finland National Park: peace and quiet on a summer evening next to the open sea
By Markku Lappalainen
Pages 22-25

Comprising islands and expanses of sea, the Eastern Gulf of Finland National Park was founded in 1982. Its land area is 600 hectares divided over around 100 islands and plans have been made to extend the protected area. In summer there is a national park guide on the island of Ulko-Tammio, conveniently accessed by waterbus from the town of Hamina. There are landing places on a couple of other islands as well. Additionally, landing and camping are permitted on numerous other islands.
Within the national park the grey seal population has increased in recent years, but over the same period of time there has been a radical decline in the ringed seal population. According to professional fishermen, the seals, which are protected, cause a good deal of damage.

Over 60 km wide in an east-west direction, the national park provides ideal nesting islets and islands for large numbers of seabirds. Razorbills, black guillemots, various kinds of gulls, terns, waders and anatids occur there in abundance. Alcids have seriously declined due to unexplained mass deaths in 1992 and 2000. The lesser black-backed gull population was reduced to one half in 1985-1995 and the production of young is poor. During the last couple of years the decline has halted and possibly a small rise in numbers may even have taken place. The Caspian tern has returned to the area to breed and the greylag goose, mute swan, cormorant and barnacle goose have increased.

The islands' habitats vary from extremely barren and maritime to startlingly lush. Although oligotrophic pine forest often covers the summits of rocky outcrops and lines shores, lush broadleaf woods with thick humus occupy depressions and gullies between rocks in the more central parts of the islands. The vegetation and birdlife are correlated; rare eastern songbirds are often heard singing in the herb-rich woods.

Play is a serious matter
By Juha Valste
Pages 36-39

Play is frequently referred to as children's work. Aside from people, many other animals play, and the more intelligent the animal the more often it plays. A raven living in Ranua Zoo had invented a game in which it pushed a twig through the mesh of its cage. When someone pushed the twig back in, the raven replied by thrusting it out again. This game often continued for several minutes.

An important function of play is to develop the combined action and co-ordination of the senses, musculature and nervature. In particular young predators learn the various stages of hunting through play. An animal can release certain stresses and aggressions through play. During play, the social hierarchy and dominance among individuals are often also established.

As with people, the reason for play among animals may be simply to produce a feeling of well being. Otters sliding down a muddy or icy river bank into the water, and the acrobatics birds sometimes engage in for several minutes in thermals are good examples of this kind of play. In the large mixed grazing herds of the savannahs young individuals of each herbivore species frolic and play together, and even with adults of other species.

Play is an important and serious matter, even though it can sometimes be great fun and even, in the case of people, lead to laughter. In play, animals learn important action models, both in their social lives and in hunting, which are essential for survival. The most intelligent animals of all may obtain ideas, action models and new solutions to old problems. Play may be some sort of free association, the creation of new connections.

Gotland - on the other side of the open sea
Text and photos by Arja and Kai Noponen
Pages 40-43

Gotland is the Baltic-s largest island. Belonging to Sweden, the island is mainly composed of limestone, making its vegetation entirely different to that on the Swedish mainland. Over 500 different vascular plant species grow along Gotland's road verges, while there are five different species of rowan. There are also a huge variety of different orchids.

Gotland's plant and bird world is unbelievably rich, much richer in fact than one might think from the island's northerly location. Its position in the middle of the Baltic, however, makes its climate far warmer than at the same latitude on the mainland. Secondly, the island gets more sunny days in summer.
Stora Karlsö lies off Gotland's west coast south of Visby.

This smaller island was one of the world's first ever conservation areas, having been protected since 1880. Despite its size, it supports almost 600 plant species, while 240 bird species were recorded there during the 1900s. Stora Karlsö also boasts Sweden's only 'bird mountain', a breeding ground for 10,000 pairs of guillemots and 5,000 pairs of razorbills.

Teksti: Leigh Plester