Bringing back the wild forest reindeer

The reindeer (Rangifer tarandus),  a.k.a. the caribou in North America, inhabits a large stretch of the Northern Hemisphere. Fourteen subspecies are currently recognized, several of which live isolated from the other subspecies. The wild forest reindeer (Rangifer tarandus fennicus) lives in Finland and Russia, and it is the only subspecies inhabiting the European Union. Wild forest reindeer were once an important game animal in Finland. However, intensive hunting led to their extinction, first in Sweden, and later, at the turn of the 19thand 20thcenturies, also in Finland. During the 1950s, the subspecies made a comeback, when a new population formed naturally in northeastern Finland, made up of individuals that migrated over the border from Russia.

Wetland ecology group_University of Helsinki_wild forest reindeer stag

Wild forest reindeer stag

The global reindeer/caribou population is in decline and the species is considered Vulnerable according to the International Union for Conservation of Nature. However, each subspecies also has its own population status, and the wild forest reindeer was classified as Near Threatened in the 2010 Red List of Finnish species. The subspecies is under pressure from human actions such as traffic, habitat change, and snowmobiling. Large carnivores also exert a great deal of predation pressure in certain areas. Finland has conservation obligations, as it is the only country in Europe where the subspecies lives.

2016 saw the beginning of an ambitious EU LIFE project for reintroducing and breeding wild forest reindeer to parts of its former habitats in two Finnish national parks (Seitseminen and Lauhanvuori). The project involved building two reintroduction enclosures, after which wild forest reindeer males (stags) and females (does) were housed in the enclosures. Some of the individuals were caught from the wild, while the rest were brought in from various zoos. More individuals will be brought in over the course of the reintroduction scheme. This will enable keeping the genetic diversity of the breeding and reintroduced populations at high enough levels. The reindeer will be fed lichen and reindeer fodder, to supplement what the individuals are able to forage from nature. The first calves were born in the enclosures last spring (2018). Currently the reindeer still live in the enclosures, but the project goal is to release the first individuals during 2019. They will still be given supplemental food e.g. in the case of a harsh winter.

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Wild forest reindeer living in the reintroduction enclosures are given supplemental food.

Widescale mammal reintroduction projects often encounter surprising situations. The birth of five wild forest reindeer calves into the reintroduction enclosures during the spring/summer of 2018 was one such event. Not because the calves were born, but because each of them is most likely a male (their gender has not been 100% determined yet). More males than females are born in reindeer/caribou populations, because they form small groups with one stag and several does. However, chance dealt an unexpected hand in the small reintroduction populations, resulting in several males and no females. Three additional does were brought into the enclosures in October 2018 to deal with this surprise.

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Calves born in the reintroduction enclosures during summer 2018.

The project is also committed to restoring several forest and peatland areas suitable for wild forest reindeer. Another task is to ensure that wild forest reindeer and the semidomesticated form of mountain reindeer (Rangifer tarandus tarandus) do not meet in the wild. Both are subspecies of the reindeer/caribou. Semidoemsticated reindeer live in North Finland, where they are cared for by the reindeer herding industry. Reindeer/caribou subspecies can reproduce with each other, which is why the genome of the wild forest reindeer must be kept clean. Otherwise we risk mixing the genomes of the two subspecies.

During the fall rutting season, wild forest reindeer form small herds with one mature stag and several does and their different-aged calves. After the rut, these herds migrate towards their wintering grounds, where several herds congregate.

More information is available on the project website. The life of wild forest reindeer can be followed via a camera set up by WWF Finland (live footage especially during summer). Best recordings from last summer are available on the YouTube site of WWF Finland (text in Finnish, but videos have no sound).


Wishing everyone a Peaceful Christmas and a Happy New Year 2019!

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Bohemian waxwings move around Finland in search of plentiful rowanberry stocks. Sometimes these sporadic migrations, known as irruptions, bring waxwings all the way to Great Britain and Continental Europe. Strong waxwing irruptions were observed in southern Finland during autumn 2018.

What do we know about the sustainability of duck harvesting in Northern Europe?

To evaluate duck harvest sustainability, we need to evaluate population size and production rate, in addition to harvest bag size. However,  these statistics are inadequate in Europe. We only have a robust evaluation of the wintering population size of ducks. Finland and Czech are the only countries conducting annual brood production surveys for ducks. Only Denmark annually collects harvest wing samples at a national level. In Finland, wing samples have been collected for a few years only. Nearly every European country produces some kind of bag statistics, but data quality is often poor. In addition, methods differ from one country to another, so comparing the results is difficult.

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Finland is the only country along the East-Atlantic flyway that conducts annual brood surveys.

All individuals are not equal in their population growth rates. Many juvenile birds die before they reach their first breeding season. Old birds are thus more important for the population than young ones. This is why harvest should be targeted at young individuals. In years of poor breeding success, the ratio of young birds is lower compared to old ones, and thus the harvest bag should be decreased to reach a sustainable harvest level.

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In addition to species, wings can also be used to determine the age and sex of ducks.

Finland and Denmark both belong to the East-Atlantic flyway. Finland is an important breeding area for several duck species. Ducks born in Finland often migrate through Denmark, while some also winter there. In a recently published study, brood production in Finland was compared to harvest bag size and wing age ratios in Finland and Denmark. Three common duck species were included in the study: the common teal (Anas crecca), Eurasian wigeon (Mareca penelope) and common goldeneye (Bucephala clangula).

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Denmark collects harvested wings on an annual level, while two periods of three-year surveys have been organised in Finland.

The study showed that the annual harvest of Finnish goldeneyes is positively correlated with their reproductive output. Additionally, the increase in brood production suggested to associate with an increase in juvenile wing ratio in the harvest bag. But, as the sample size is only six years, this result remains uncertain. This is a good start towards sustainable harvest levels. No similar association was observed for teal and wigeon. However, the wigeon harvest in Denmark increased with an increasing juvenile ratio. This study was unable to evaluate sustainable harvest levels as such. Finnish brood surveys show long-term declining trends for all the studied species, and harvest levels in Finland have concurrently dropped. However, only harvest levels of goldeneye have decreased in Denmark.

This study emphasises a need to better define population units, before harvest sustainability can be assessed. Our current knowledge is not enough to say whether duck harvest is sustainable even in Northern Europe. With declining brood production trends, we urgently need to follow how well the harvest reflects this population change.

Read more:

Holopainen et al. 2018. Associations between duck harvest, hunting wing ratios and measures of reproductive output in Northern Europe. European Journal of Wildlife Research


Man’s best friend as a field assistant

The dog has been man’s best friend for tens of thousands of years. Our friend has travelled to the moon for us (Laika the dog was the first living organism in space), guards our homes, assists in hunting, helps weed out drug-related crime and helps scan for cancer tumours. Now our intelligent and multifaced companion has become a new use and help.

Dogs are now serving as field assistants in ecological research. Ten years ago, Natural Resources Institute Finland began utilizing game bird dogs in willow ptarmigan (Lagopus lagopus) surveys in Lapland. Previously the surveys were conducted with human help.

Game bird dogs are utilized in willow ptarmigan (Lagopus lagopus) surveys in Lapland. © Veli-Matti Väänänen

In the willow ptarmigan surveys, Lapland is divided into 45 areas and these areas contain 171 survey sectors altogether. Dogs assist in the counting of willow ptarmigans from 670 kilometers. Usually two humans at a time take part in the surveys. One of them guides the dog while the other observes that the human and dog stay in their sector and count all the willow ptarmigans. Only one dog works at a time, although several dogs present may be present.


The dog’s purpose is to silently search for willow ptarmigans and after finding birds, the dog will freeze and then flush them into flight. Once the birds are flying, the surveyor counts them. In addition to counting, the person also determines the sex and age of the birds, and estimates the point where the flock was flushed. This method provides an estimate of population density. The population density of Finnish willow ptarmigans is 7.5 individuals per square kilometer. This estimate was received from last year’s surveys. The yearly variation in willow ptarmigan population density is great. Population dynamics are based on reproductive success. The willow ptarmigan population size can vary from tens of thousands to some hundreds of thousands in the Lapland region.

The dog breed makes no difference in the surveys, but game bird dogs are most suitable for the purpose. © Veli-Matti Väänänen

Finland is somewhat behind in utilizing this survey method. Sweden and Norway have used game bird dogs since the 1990s. The dogs must be experienced in flushing birds into flight, rather than being successful in working tests. Dogs usually learn from hunting situations. Game bird dogs are bred and trained for seeking and disturbing birds into flight. The dog breed makes no difference in the surveys, but game bird dogs are most suitable for the purpose.

Primeval beaver soup

Life on Earth has originated in water, in the so-called primeval soup. Chemical reactions in water produced a series of processes from which life on Earth began evolving. The main components of life are composed of carbon, hydrogen and oxygen.


Beavers act as cooks of the primeval soup of water systems in the Northern Hemisphere. Boreal water systems are fairly oligotrophic and infertile. An oligotrophic water system means that it does not provide a habitat for diverse assemblages of plant and animal species. Only a few species are able to live in such habitats. Oligotrophic conditions originate from the chemical conditions of a water system. Furthermore, oligotrophic water systems do not contain that much dissolved organic compounds (organic = carbon-carbon compound).

A beaver flood alters the oligotrophic water systems in the boreal zone into a lush one by changing the habitat’s water chemistry. © Sari Holopainen

A beaver flood alters an oligotrophic water system into a lush one by changing the habitat’s water chemistry. The water level rises into the surrounding land ecosystem because of the dam, and washes various materials and substances from the shore into the water system. Most of these materials originate from organisms, mainly vegetation.


Plants consist of various proteins, lipids and carbon hydrates, whose principal components are carbon, hydrate and oxygen, the main elements of life. Therefore, plenty of carbon and hydrate, in addition to some phosphorus, are washed into water systems because of beaver dams.


The Carbon in water is usually in a dissolved form, which is called DOC (dissolved organic carbon). When a beaver has dammed a water system, the DOC concentration increases significantly in the water system. The beaver’s effect on the carbon is not permanent, as it converts to initial levels after the flooding has lasted for four to six years. Organic carbon washed from the shores begins gradually sinking to the bottom of the water system and it can also be released into the atmosphere in the form of carbon dioxide and methane.


The eutrophic primeval soup cooked by beavers creates a series of events that consequently attracts very versatile plant and animal species to the water system. The beaver effect is evident in several food web levels. Organic carbon and other nutrients are consumed by phytoplankton and aquatic vegetation, which in turn benefit for example aquatic invertebrates and tadpoles. Abundant invertebrate numbers, on the other hand, provide food for fish and ducklings. Oligotrophic water systems in the boreal zone are altered into biodiversity oases by beaver activity.


Further reading: Vehkaoja ym. (2015). Spatiotemporal dynamics of boreal landscapes with ecosystem engineers: beavers influence the biogeochemistry of small lakes. Biogeochemisty.

All cavities are not equal

Come spring (late winter), the forests are bustling. Cavity-dwelling animals search for tree crevices and holes in which to lay their eggs and raise their offspring. Tree cavities provide a stable environment for successful nesting.

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Natural cavities are usually found in old wide trees, where the inner temperature of such cavities remains more stable than outside temperatures.

Only one problem remains. Cavities usually form in old or, at the least, decomposing trees, but forestry practices simplify forest cover composition. Fewer trees surpass forestry practice recommendation ages, so our forests have less large aging trees in which fungi can spread. More tree cavities are desperately needed. Nest boxes are our solution to this problem. The idea is simple: anyone can build a nest box and hang it on their own land (or somebody else’s with permission). This has helped boost the populations of certain cavity-nesters such as pied flycatchers (Ficedula hypoleuca) and great tits (Parus major).

It would be nice to think that we have solved the cavity problem, or that the problem will be solved if we raise the number of nest boxes to sufficient levels. But it’s not that simple. Several researchers have studied the functionality of nest boxes over the years. The microhabitats of tree cavities and nest boxes differ from each other in relation to temperature and moisture. Wroclaw University researchers were the most recent group to prove this distinction, but they also demonstrated that these functional differences drive the marsh tit (Poecile palustris) to choose natural cavities over nest boxes. Their study was conducted in two forests; the other had an unlimited number of tree cavities, while nest boxes were the only nesting option in the other forest. The marsh tits preferred natural cavities with thick walls buffering the holes from outside temperatures. And birds are not the only species that have been shown to prefer natural cavities, for example certain bats and the common brushtail possum (Trichosurus vulpecula) will settle in natural cavities due to their more stable microclimates.

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The common brushtail possum is an Australian mammal that nests in tree cavities. Picture: Wikimedia Commons. By user:benjamint444 modified by Tony Wills [GFDL]

Nest box temperatures in the Wroclaw study fluctuated significantly more than the inner temperatures of tree cavities. Nest box temperature also changed at the same rate as outside temperatures. Nest box temperatures can therefore rise to dangerous levels during the summer, to where chicks are at higher risk of dying from excessive heat compared to broods in tree cavities. During the winter, nest box temperatures drop to lower levels than cavity temperatures, decreasing the shelter effect that many small birds utilize to survive the harsh cold.

Nest boxes also average lower air moisture levels compared to natural cavities. This may hinder mold from growing in the nest boxes, but concurrently lower moisture may encourage wasps (Vespidae) and tree bumblebees (Bombus hypnorum) to settle in nest boxes, making them inaccessible for birds. Fleas (Siphonaptera) may also increase in dry and warm conditions, so the number of competitors and ectoparasites may increase.

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Woodpeckers excavate cavities in decomposing trees and standing dead wood

To cap, nest boxes and natural cavities do not replace each other from a structural point of view and not all species will nest in boxes. The majority of nest boxes are so-called standard models, i.e. they are copies of each other in terms of dimensions and flight hole diameter. In real life, a standard model nest box is only accepted by a limited number of cavity dwellers. It is therefore imperative to conserve aging and decomposing trees, as their cavities are never of standard shape or size. If nothing else, decomposing trees in our yards should be conserved; trees can always be cut to a height that ensures they are of no danger to nearby buildings or people. Such standing dead wood is very rare in current heavily managed forests. With a standing birch dead wood tree it is even possible to attract the picky willow tit (Poecile montanus) to your yard.

The next best alternative is to ensure the structural heterogeneity of nest boxes, i.e. build boxes that are also suitable for species such as the common redstart (Phoenicurus phoenicurus), owls (Strigidae), treecreepers (Certhiasp.), and even certain mammals such as flying squirrels (Pteromys volans). This may require a little more trial and error, but it is the only way of maximizing the nesting alternatives in managed forests. Ideas for nest box designs abound online, Pinterest for example has a huge selection of box models. However, it is important to follow nest box construction instructions issued e.g. by the BTO and Audubon Society or these general safety instructions, to make sure that the boxes are as safe as possible for birds. Nest box positioning is also important; foliage has a protective effect, and the microhabitat of nest boxes positioned under foliage therefore remains more stable than in sun-exposed areas.

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Blue tits often utilize nest boxes.

Adding insulating materials to nest boxes is one way of adding to the inventiveness of nest box construction. To mimic the microclimates of natural cavities, a team of Australian researchers recently compared nest boxes that had been fitted with three types of insulating or heat-reflecting materials. Nest box temperatures remained most stable around the clock in nest boxes insulated with polystyrene foam. The inner temperature of one polystyrene-fitted nest box was nearly six degrees Celsius less than outside temperatures. Nighttime inner temperatures were also higher in the polystyrene nest boxes compared to non-insulated boxes when a heat-producing pillow was placed in the insulated and non-insulated nest boxes, to mimic the effect of birds spending the night in the boxes. The Australian study showed insulation had a more significant effect on nest box temperatures than nest box placement in a shady or sunny location. However, for the environment and breathability, it is probably better to use some type of natural fiber insulation in nest boxes. Also, insulated nest boxes are not enough to fill the void created by the disappearance of natural tree cavities, as the study showed that the temperature fluctuation of even the polystyrene-fitted nest boxes was greater that of natural cavities.

P.S. It is currently trendy to set up cool or “beautiful” nest boxes without thinking about their safety at all. Not a good idea! For example, ceramic bird boxes are much worse insulators than wooden ones, and painted boxes should use lead-free paint.

The secret wildlife of golf courses

The cool morning air has strewn the lawn with small dewdrops. The green is bathed in flickering mist and shining dewdrops. Soon the green is filled with the sibilant sound of golf balls and walking golfers, but for a while, the course still belongs to someone else.

Water hazards of Hiekkaharju Golf in Vantaa (in the Helsinki metropolis area) provide suitable habitats for diverse species. Picture borrowed from

Keimola Golf, located in Vantaa (in the Helsinki metropolis area in Finland), is a true paradise for birds and amphibians. Whooper swan (Cygnus cygnus), common goldeneye (Bucephala clangula), and horned grebe (Podiceps auritus) pairs nest in the largest water hazard. In addition, the black woodpecker (Dryocopus martius) nests nearby. The number of horned grebes has declined worldwide, and the species is considered vulnerable in Finland. The Finnish population has decreased from 3000 to 6000 nesting pairs in the 1980s to the present 1200–1700 nesting pairs.

On the other hand, all Finnish amphibian species, except one, can be found living in one of the smallest water hazards of Keimola Golf. Only the Northern crested newt (Triturus cristatus) does not occur there. The Northern crested newt is critically endangered in Finland, and can only be found in a few places in eastern Finland. In spring, the common frog (Rana temporaria), the moor frog (Rana arvalis), and the common toad (Bufo bufo) croak vigorously. The smooth newt (Lissotriton vulgaris) does not croak, but mating males bring tropical colors into an otherwise brownish landscape.

Mating smooth newt males are springtime color spots in a wetland. ©Mia Vehkaoja

By Midsummer, golf courses are swarming. On dry land, golfers enjoy their sport in warm summer weather, while hatched ducklings and tadpoles are concurrently going through growth spurts around the water hazards. Golf courses provide lots of nutrition for ducklings and tadpoles. Water hazards, as most wetlands, are habitats for several invertebrates, such as mosquito (Culicidae), nematocera (Nematocera), and trichoptera larvae, as well as for phyto- and zooplankton. Amphibians prefer open and sunny wetlands because higher temperatures escalate tadpole development. Ducklings, on the other hand, prefer wetlands with luxuriant shoreline vegetation (for example club rushes and sedges). Vegetation provides cover against predation.

Luxuriant shoreline vegetation provides cover for ducklings against predation, whereas openness increases water temperature and escalates tadpole development. ©Mia Vehkaoja

Golf courses are oases for wetland-associated species, especially in urban environments, where most wetlands are isolated from each other. For numerous species, water hazards and golf greens offer nearly free access between wetlands and other habitats. Golf courses are currently not planned to consider nature and its needs. What if nature were taken into account during planning, with at least a 10% effort? Keimola Golf’s extraordinary biodiversity has arisen through chance. Waterfowl diversity is due to an island left in the middle of the largest water hazard. The island has some ten trees and bushes. The whooper swan and common goldeneye nest on this island.

Both national and international designers have planned Finnish golf courses. Keimola Golf was planned in Great Britain. More and more, architects plan golf courses by initially outlining the routes, after which the planning is continued on-site concurrently while the course is being constructed. This method enables taking nature into account during the planning process.

Architects could pay attention to small things that benefit animal and plant species when planning water hazards and groves. For example, bushes and shoreline vegetation could be left next to the shoreline that is not close to the green. This has been done at Keimola Golf. Paying attention to such small details does not even cause additional costs. Furthermore, most golfers enjoy the sport because they can be outside and “enjoy” nature. If nature were actually taken into account during planning, golfers could actually play their sport “in the wild”.