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.

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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.

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.

Helping out or avoiding risks

Social insects have numerous pathogens that can spread simultaneously in a densely packed colony. Mild exposure to one disease may not increase an individual’s risk of dying, but it does increase the individual’s risk of concurrently contracting another pathogen. Such double diseases are called superinfections, and they lead to death significantly more often than contracting one disease at a time does.

Preventing the spread of a pathogen within a colony is highly important for social insects. Other individuals can treat their sick counterparts either by helping them or by being aggressive. Help can come in the form of grooming, which serves to clean sick individuals of a potential pathogen, or spraying, where infected individuals are hosed off with antimicrobial chemicals. These chemicals are produced in the bodies of certain ant species, which spray the antimicrobials into their surroundings by increasing their internal pressure. On the other hand, aggression appears as biting and dragging of infected animals, which is done to prevent pathogens from spreading deeper into a colony by removing sick individuals from the colony.

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Ants are social insects. They live in colonies that can grow to tens of thousands of individuals © Sari Holopainen

To test how colony mates react to sick individuals, Austrian scientists conducted a study on Lasius neglectus ants. The scientists placed mildly sick ants, infected with one of two fungal pathogens, into a colony. The colony also housed healthy individuals used as controls. Sick individuals could therefore encounter healthy individuals, individuals with the same disease, or individuals suffering from the different pathogen. The controls on the other hand ran into other healthy ants or ants suffering from one of the two diseases. The researchers wished to see whether previous infection altered the behavior of the ants when meeting an infected individual. They were also interested in testing whether the ants reacted differently to individuals infected by the same pathogen as to individuals carrying the other pathogen.

The studied ant species is usually not aggressive towards its colony mates. However, during the experiment, infected individuals often began biting and dragging encountered individuals if they were also sick. Healthy individuals did not react to their diseased counterparts in the same way. Diseased individuals also sprayed other infected ants more often than healthy individuals did. Spraying was more common if the diseased individual suffered from the different fungus than did the sprayer. Grooming was most common when sick individuals with the same pathogen crossed paths.

In other words, infected ants are more aggressive towards other disease carriers, but concurrently they can alter their behavior according to the situation, and choose the safest decontamination method available. This is determined by whether the encountered ant is infected by the same or the other pathogen. Grooming requires individuals to be close to each other, but if both ants have the same infection, the risk of a new infection is minimal. Spraying can be done from a greater distance, in which case individuals don’t come into close contact. This helps sick individuals from contracting a superinfection, which would most probably be lethal.

The scientists were also able to determine that this risk aversion pays off, as mildly sick ants were successful at avoiding a superinfection. Both individuals therefore benefit from altering their behavior, also known as behavioral plasticity. This is extremely important for social insects in densely inhabited colonies, where sick individuals cannot be avoided.

Cleaning is not the only way in which colony insects help each other out. Another recent example comes from German scientists, who observed an African ant species (Megaponera analis) to tend to its injured individuals by licking. Their saliva is believed to contain antimicrobial substances that assist healing. The species often raids termite mounds, so an individual’s injury risk is great. Uninjured ants must make the choice of either helping injured counterparts back to the colony for medical assistance or not. Helping increases an uninjured individual’s risk of suffering injury. However, it is in the colony’s interest to treat as many individuals as possible.

A YouTube video showing uninjured ants tending to injured individuals

Hawks for hunting

Falconry is a centuries-old form of hunting in numerous countries around the world. It is considered an integral aspect of many cultures, and was therefore added to the UNESCO Lists of Intangible Cultural Heritage as a living human heritage element in 2010.

Falconry involves a trained bird of prey that is instructed by a falconer to hunt its natural prey species. The birds can be falcons, hawks, or eagles: even a few owl species have successfully been used. The falconer releases his bird once he has seen a potential prey animal. The bird flies after the prey, and pins it to the ground. The falconer follows, kills the prey, and gives the hawk a compensatory food reward. Falconry can be practiced during regular hunting seasons.

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Several cultures utilize birds of prey for hunting. Lotta the goshawk hunts in Finland. ©Markku Kallinen

Falconry is practiced in many Arab nations, European countries (e.g. Great Britain and the Czech Republic), and in most US states, to name a few examples. The International Association for Falconry (IAF) carefully regulates falconry. The association’s objective is to advance the protection and conservation of birds of prey through falconry and awareness raising.

Despite conservation efforts, many people harbor negative feelings towards falconry. And true problems do exist; certain countries allow the crossbreeding of species. If hybrid hunting hawks manage to escape from captivity, they can weaken the genetic purity of local birds. Alien species are also used in certain areas. For example, Britain has imported Harris’s hawks (Parabuteo unicinctus) into the country for pheasant hunting, but escapees have been reported nesting in the wild. The ethics behind captive wild bird species and breeding them in captivity also remains an issue. On the other hand, falconry has also managed to lessen prejudices that people have harbored against birds of prey in many countries, and falconry organizations further the conservation of both birds of prey and other bird species by e.g. raising awareness and campaigning against illegal animal trafficking.

At one time, falconry was also popular in Finland, where the goshawk (Accipiter gentilis) was the bird of prey most used. Falconry is technically legal according to Finnish hunting legislation, but actually obtaining a hunting hawk is not easy in practice. Goshawks are protected in the country, so a native bird cannot be captured. Therefore a bird must be brought in from abroad. The bird cannot be an alien species, and individuals brought in must also be sterile, as goshawks in other countries are of different populations than in Finland.

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Markku and Lotta mainly hunt mountain hare. ©Pia Kallinen

However, Finland certifiably has one pair of hunting goshawk and falconer. Markku Kallinen and Lotta the goshawk uphold an old hunting tradition that disappeared during the 1960s. Markku and Lotta mainly hunt mountain hare (Lepus timidus). See a video of Lotta feeding, filmed by Pia Kallinen.

Lotta’s activities can be followed (in Finnish) at

David and Goliath – a story of bark beetles

Bark beetles (Scolytinae) are small beetles a few millimeters in size. Their larva develop under tree bark eating the phloem, xylem, and cambium layers. Certain species cause extensive forest damage by killing healthy trees, while others only impact weakened individuals. The eating patterns (called galleries) and the trees’ defensive reactions cause disturbances in the nutrient and water cycling within the trunks. The trees literally dry to death.

Bark beetles can be detected by the gallery patterns they leave on tree trunks. These patterns are species-specific, and often very beautiful. The patterns can be used to recognize infestations and begin warding off the worst damage. Then again, the gallery patterns cannot be seen until the tree bark falls off.

Bark beetles also have a secret weapon: wood-staining fungi. This group of fungi includes several species that damage wood or cause serious diseases to trees. Bark beetles and wood-staining fungi have developed various relationships such as the ambrosia beetles that spread certain fungi species into their galleries to farm them for food. Wood-staining fungi benefit from the bark beetles transporting them to new trees, and have developed exceptionally sticky spores that attach to adult beetles as they are preparing to disperse. Bark beetles also benefit: the fungi weaken new tree individuals, giving adult bark beetles the opportunity to infest and lay their eggs in these trees.


A possible wood-staining fungus is spreading beneath the bark of a birch infested by the birch bark beetle. ©Stella Thompson

It’s hard to believe that tiny beetles and even more minuscule fungi can kill gigantic trees. Situations where a bark beetle or fungi spreads to a new geographical region among lumber are particularly devastating. The new host trees have no immunity or defense mechanisms against this new organism and the alien species spreads like wildfire.

Dutch elm disease is a prime example of this. Ophiostoma ulmi, a fungus killing elm shoots spread from Asia initially to Europe and then, fueled by the post-World War I reconstruction boom, from Europe to North America in lumber. European elm species coped with the disease slightly better than their North American cousins. European elms also died, but the spread of the disease around Europe took several decades and finally the outbreak waned. 10–40% of the elms died, depending on the country in question. The situation was very different in North America. The American elm (Ulmus americana), a very popular urban and ornamental tree, formed large forests in the eastern areas of the continent. It narrowly escaped extinction through active eradication and education measures such as campaigns forbidding the transportation of firewood outside infected states. Unfortunately, a new, much more virulent fungus (Ophiostoma nova-ulmi) causing Dutch elm disease spread to Europe and North America during the 1940s. This fungus has caused the near annihilation of elms from several European countries. As of yet Finland has mostly been spared by the disease, but this may change with a warming climate that allows beetles belonging to the Scolytus genus that carry Dutch elm disease to overwinter in more northern regions. These beetles are already found on the northern coast of Estonia and in the Stockholm area of Sweden. The birch bark beetle (Scolytus ratzeburgi), commonly found in Finland, does not spread Dutch elm disease as it has specialized in solely utilizing birch trees.

However, the birch bark beetle spreads the Ophiostoma karelicum -fungus. Trappings


The presence of birch bark beetles can be detected by their unique eating patterns. ©Stella Thompson

conducted during 2008 and 2009 for a study carried out in Norway, Finland, and Russia revealed the prevalence of O. karelicum: every single birch bark beetle individual carried the fungus, which was also found in each of the beetle’s galleries that were searched. The life cycle and ecology of O. karelicum is very similar to the fungi spreading Dutch elm disease, and the commonness of the fungus and the birch bark beetle means a very high risk of the disease spreading to e.g. North America. The birch species native to North America would most probably have no resistance to the disease.

On the other hand, pitch canker (Gibberella circinata) is a fungus spread by bark beetles, originating in North America, which has now spread to Europe where it causes pine mortality. The Scots pine (Pinus sylvestris), native to e.g. Finland, is especially susceptible, but the disease has not spread as far north as Scandinavia yet.

To make these dynamics even more complicated, several mite species have also been shown to transport or act as the primary hosts of wood-staining fungi. These mites are in turn spread by bark beetles. The relationships and interactions between these three organisms are still poorly understood.

The disease resistance of tree species can be increased through cultivation. American elm cultivars more resistant to Dutch elm disease have been found, and their disease resistance has been further enhanced through cultivation. These cultivars are most probably the reason that elm forests still exist today in North America, although the age and size composition of these forests has changed considerably with the death of the old and large trees. Biological and chemical disease control is also a possibility: fungicides can be injected into live trees to stop the spread of specific diseases. Six fungicides combating Dutch elm disease are currently on the market in the US.

Similar control measures can most probably be developed against O. karelicum. However, widespread injection campaigns are difficult to implement. In the US, Dutch elm disease is mainly controlled by injecting individual ornamental or urban trees. Injection control as an effective eradication measure requires more development before it becomes a feasible tool for preventing damage caused by alien species.

Crawlers and fliers – how to study forest insects

Studying insects is interesting yet challenging. Determining individuals to the species level


The presence of birch bark beetles can be detected by their unique eating patterns. ©Stella Thompson

nearly always requires capturing them first, although some species, such as the birch bark beetle (Scolytus ratzeburgi), can be identified by the unique pattern they leave on tree trunks. However, it is almost always necessary to use various types of traps to capture individuals if identifying the insect species present at a certain site is the main objective of a study. For example, butterflies are trapped during the night using light traps, and the occurrence of certain protected species can be confirmed using feromone traps that use synthetic lures as bait. Traps can be dug into the ground, lifted high up into tree canopies, or attached to the insides of hollow tree trunks.

As my PhD research I am assessing how beavers affect forest beetle populations. I have several research questions:  do beaver-induced flood zones have different beetle species assemblages than other areas, do the increased moisture and sunlight conditions in the flood zone affect species assemblage, and do beaver areas advance or hinder potential forest pest or protected species. My research combines a game species with widespread effects on its surroundings and forest beetles, several species of which have become scarce and require protection. Beaver-induced flooding and the species’ habit of felling tree trunks may locally disturb forest owners, but my study is looking into whether beavers’ actions facilitate or disturb forest pests. Combining game and insect research is cool, and generates new information on which to base decision-making for future protection measures, beaver population management, and even for using beavers as a natural tool for restoring degraded wetlands and forests.

Window traps are widely used for determining the insect assemblages of sites. Window traps cannot be used to capture specific insect groups, because all sorts of invertebrates ranging from flies to pseudoscorpions and wasps to beetles creep or fly into them. Window traps are very simple: the trap is attached to a tree trunk or set to hang between two trees. Insects crawl or fly into the plastic plexiglas frame and then fall through the funnel into a liquid-filled container at the bottom. The container is filled halfway with water, dishwashing fluid, and salt. The dishwashing fluid prevents the insects from regaining flight, consequently drowning them. The salt helps preserve the insects until the trap is emptied out, which happens about once a month. I have 120 traps spread out at several sites, so every summer I collect about 600 samples.

Unfortunately other creatures may sometimes end up caught in the window traps. So far I have inadvertently captured a few common lizards and a bat. This is always disappointing, because an individual dying for nothing does not advance research or science in any way. In the same way it is frustrating if you unintentionally set up a trap on a tree trunk that an ant colony uses as its route. Hundreds or even thousands of ants may drown in the window trap. As my own study focuses on beetles, I cannot utilize the ants in any way. At least this does not happen very often.

After the trap container has been emptied the gathered sample is sifted through using tweezers and a microscope, to separate the insect groups that I am interest in. Next the individuals are determined to the necessary level. Sometimes determining the family level is enough, but if making conservation decisions or gaining new information on certain species is the goal, it is usually necessary to determine individual insects to the species level. How this is done depends on the order in question, e.g. beetles are often recognized by their ankles and genitals.

Occasionally you come across data deficient species, i.e. species that are not well known or understood. Species, genera, and families are determined using identification keys, which are sometimes incomplete. For example, currently the best key for identifying Finnish rove beetles is in German, and for several families the most complete keys are in Russian. So I’m currently kind of happy that I studied German in middle and high school. I guess next I should begin uncovering the secrets of Russian vocabulary.