Beavers facilitate Teals at different scales

Wetland ecology group_University of Helsinki_Teal

Teal broods utilize beaver ponds.

Blog text by Petri Nummi, Eeva-Maria Suontakanen, Sari Holopainen and Veli-Matti Väänänen “Beavers facilitate Teals at different scales” is now available on the Ibis website.

Advertisements

There and back again – a mire’s tale

In a remote country lived a rich mire species community. But that was once upon a time, when Finland was a land of mires. Nowadays, only fragmented pieces are left in the southern region, while large natural mires can still be found in Lapland. Nevertheless, only one third of historical levels remain. Most mireswere dried due to farming and forestry. Ditches were dug to gather water from ca. 6 million hectares of mires. This affected the hydrology and further the ecology of these wet ecosystems. Several plant and animal species are adapted to mires, and have thus suffered from habitat loss and fragmentation. For example, forest grouse and bean geese (Anser fabalis) utilize mires during their breeding period. Due to ditching, mires stop producing their ecosystem services, because berry production and game bird populations (these are cultural and provisioning ecosystem services), decrease, and thus the recreational values of the areas lessen.

Wetland ecology group_University of Helsinki_Mire_Cloudberry

Cloudberry (Rubus chamaemorus) grows on mires and benefits from restoration activities.

Finland has about 10 million hectares of dried mires, more than half of which have been utilized by forestry. However, about a fifth of this area does not produce wood well enough for it to be profitable. After several centuries of mire destruction,  a change is now in the air. Finnish mires are being restored with increasing effort. For example, in 2017 Metsähallitus (the Park and Forest Service) began an EU-funded project called Hydrology LIFE. The project aims to safeguard not just mires, but also small water bodies and important bird lakes in 103 Natura 2000 areas. The project restores and protects mires.

Wetland ecology group_University of Helsinki_duck_mire_restoration_hydrology

Mire hydrology can be restored by blocking ditches.

Hydrology is the most important issue to consider when restoring a mire. Blocking ditches leads to changes in water balance, and eventually to active peat formation, which is basically the definition of a mire. After the ditches are blocked, water levels normally rise rapidly to correspond with the natural situation. However, actual peatland processes return at a much slower speed. Forest vegetation is slowly replaced by mire vegetation, starting from the ditches. The processes take a long time, so whether or not the original mire ecosystem returns is yet to be seen. It is also possible that we are actually just creating new mire types.

Wetland ecology group_University of Helsinki_Elimyssalo_mire_peatland_forest reindeer

Elimyssalo nature conservation area in Eastern Finland consists of various peatland types. The area is an important calving place for wild forest reindeer (Rangifer tarandus fennicus).

Helping forest grouse

Wetland ecology group_University of Helsinki_hazel grouse

Forest grouse utilize peatland-forest ecotones. The hazel grouse (Tetrastes bonasia) population in Finland has suffered from peatland loss.

Peatland-forest ecotones are key environments for forest grouse, but unfortunately these areas are becoming very rare. The willow ptarmigan (Lagopus lagopus) has suffered from mire fragmentation in Finland. Ptarmigan habitats are fragmented especially in Southern Finland, and thus there are small populations living far from each other. Luckily, local people are usually interested in peatland restoration that helps species such as the willow ptarmigan. Several good examples exist of how ptarmigans have accepted restored peatlands. The Finnish Association for Nature Conservation has a project “SuoMaa”, which began in 2016, and targets protecting and restoring taiga nature. One of the aims is to restore peatlands to support and enlarge a ptarmigan breeding peatland network and create connections between strong and threatened populations.

 

Read more

Hydrologia-Life

Suomen metsäkanalintukantojen hoitosuunnitelma

Restoration of peatlands, Luke

 

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.

wetland ecology group_University of Helsinki_ants

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.

Wetland ecology group_Stella Thompson_University of Helsinki_falconry

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.

Wetland ecology group_Stella Thompson_University of Helsinki_falconry

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 https://www.facebook.com/haukkametsastys/

Colour matters

Colour change is a surprisingly widespread feature in the animal kingdom. Rapid colour change occurs in both invertebrates and vertebrates. The feature has been observed in crustaceans, insects, cephalopods, amphibians, reptiles and fish.

There are two main methods for changing colour: morphological and physiological colour change. Morphological colour change is based on changes in the number and quality of pigmentophores, whereas physiological colour change is based on changes in the number of organella within the pigmentophores. Melanophores are the most common pigmentophores to have melanosomes. Physiological colour change is much faster than morphological colour change. It can happen in microseconds. Physiological colour change is regulated by the neuromuscular system in cephalopods and by the neuroendocrine system in other classes. Environmental factors, such as background, lighting conditions, temperature and moisture, along with behaviour and stress can trigger physiological colour change.

Animals capable of changing colour usually have more than one colour-change strategy. Environment, the number of predators, predator species and the presence of individuals of the same species influence the colour-change strategy. For example, the daisy parrotfish (or bullethead parrotfish, Chlorurus sordidus) has three different colourations: individuals have stripes, are all black or have an eye-dot on the tail. The purpose of the eye-dot is to frighten predators, whereas the all-black daisy parrotfish tries to blend in with its background and the striped daisy parrotfish tries to bluff or dazzle its predators. The occurrence of these colourations is influenced by environmental background, the body size of the daisy parrotfish and its social relationships. On the other hand, the common cuttlefish (Sepia officinalis) chooses its strategy by whether a predator hunts using vision or chemical signals (watch how the common cuttlefish changes its colour). Chameleons (Chamaeleonidae), however, change their colour according to the environmental background rather than to mimic or to frighten.

The common octopus (Octopus vulgaris) can change its colour. © Sari Holopainen

Temperature affects the melanocyte-stimulating hormone (MSH) in many colour-changing animals such as fish, amphibians, reptiles and crustaceans. MSH is in charge of dispersing melanin. Changing to a dark or light colour helps an animal to either reflect or absorb heat. On the other hand, changing colour can concurrently predispose the animal to predation, because the animal is unable to blend in with its environment. The colour change of over 25 desert reptile species has been proven to depend on both environmental temperature and body temperature regulation. When it gets very warm (over +40°C) reptiles change to a lighter colour despite their background being somewhat dark. The reptiles usually still escape from predation because predators are inactive at such high temperatures. In proportion, when it gets cooler reptiles become darker than their environment, especially if they are near to cover.

Wetlands, the Earth’s kidneys

Wetlands are one of the world’s most important ecosystems. They are referred to as the “Earth’s kidneys” and that comparison could not be more accurate. Wetlands truly are as important to the planet as kidneys are to humans, with one exception: humans can survive with only one kidney, but the Earth cannot.

Kidneys are in charge of humans’ fluid balance. If we are dehydrated, our kidneys try to preserve as much water in our bodies as possible, and when we have excess water our bodies, our kidneys work to discharge the extra water. Wetlands work in the same way. They mitigate both floods and droughts by absorbing and recharging water.

A wetland photographed from a drone. © Antti Nykänen

In addition to fluid balance, kidneys are also responsible for removing unnecessary and hazardous substances, such as waste products and medical substances. In resemblance to our kidneys, wetlands purify our natural waters. They filter and remove nutrients and pollutants from our rain and floodwaters. Extra nutrients will sink to the bottom of the wetland and hence are available for wetland vegetation. Kidneys purify 1750 litres of blood every day, but the water purification ability of global wetlands is 30-fold. Wetlands purify 30 cubic litres of water daily.

Unfortunately, the world has lost approximately half of its wetlands, and Europe alone has destroyed and altered two-thirds of its wetlands. We need strong actions to retain the Earth’s functioning.

The value of wetlands is essential in urban environments, where nutrient and pollutant levels are manyfold compared to more natural environments. Urban wetlands should be seen as important and cheap tools to purify our stormwaters, along with maintaining biodiversity within cities.

A Moorhen (Gallinula chloropus) chick at a wetland in Finland. © Mia Vehkaoja

Luckily, the Ramsar Convention has acknowledged the importance of urban wetlands and themed this year’s World Wetland Day as “Wetlands for a Sustainable Urban Future”. Happy World Wetland Day 2018! Let’s appreciate the Earth’s vital organs.

Whooper swans don’t out-graze wigeons

A few decades ago the whoopers swan (Cygnus cygnus) was an endangered and rare species in Finland. It only bred in remote lakes and people rarely saw them. The population increase of whooper swans after protection is one of the success stories in Finnish nature conservation. Nowadays the swans can be heard gaggling all around Finland. The whooper swan is a large bird, and it thus consumes a lot of vegetation. Water horsetail (Equisetum fluviatile) is one of its favourites.

The whooper swan population has increased greatly, and their gaggling can be heard widely in Finland.

Certain other species also prefer water horsetails. For example, wigeon (Mareca penelope) broods forage within the horsetail growths searching for emerging invertebrates. A study published earlier this year showed that the water horsetail is disappearing from Finnish and Swedish lakes. The reasons for this pattern are unknown, but one possible explanation could be increased grazing pressure. Whooper swans effectively utilize horsetails, and swan grazing was therefore suspected to be influencing the disappearance of the horsetail. Wigeon populations have concurrently shown a worrying decrease.

A recently published study conducted of 60 Finnish and Swedish lakes utilized vegetation and waterbird data gathered in the early 1990s and in 2016. The study area widely covers the boreal, reaching from southern Sweden to Finnish Lapland. The whooper swan population increased strongly during the study period. Researchers studied whether whooper swans’ grazing on water horsetail is causing the negative trend in the wigeon population. Pair counts were used to indicate waterbird communities, and thus any changes caused during the brood time were not shown.

Whooper swans are grazers that have to consume a great deal of vegetation to survive.

The study showed that whooper swans strongly preferred lakes with horsetails during the 1990s, but this connections is not seen anymore. While the number of swan-occupied lakes has increased, the number of horsetail lakes has decreased dramatically. However, it appears that swans and disappearing horsetails do not associate, because the horsetail has also been from lakes where swans don’t occur. The horsetail has increased in some swan-occupied lakes.

The number of lakes used by wigeon has decreased, but swans are apparently not causing this. Wigeon loss has not been stronger on lakes occupied by swans. Quite the opposite, as wigeons and swans appear to positively correlate. Even though wigeons prefer horsetail lakes, their disappearance is not associated with the horsetail loss occurring in the study lakes, which suggests that wigeons can also utilize other lake types. On the other hand, the researchers note that this study  did not considered the critical brood time, when the foraging opportunities among the horsetail growths are especially important. Thus it may still be possible that wigeons are affected by horsetail loss, but this effect only appears during the brood time.

Read more:

Pöysä et al. 2017. Recovering Whooper Swans do not cause a decline in Eurasian Wigeon via their grazing impact on habitat. Journal of Ornithology.

Pöysä et al. 2017. Habitat associations and habitat change: seeking explanation for population decline in breeding Eurasian wigeon Anas penelope. Hydrobiologia.

Blog text: Vanishing wigeons and fading horsetails