Guidelines for Nordic building regulations regarding indoor air quality

A subcommittee of the Nordic Committee for Building Codes has released guidelines for building regulations regarding indoor air quality, especially concerning ventilation. The main features of the guidelines, such as acceptable outdoor air quality for ventilation and minimum outdoor air flows for dwellings and offices, are presented and discussed. Mechanical ventilation is, in principle, required in all buildings including dwellings, due to the requirement of a minimum outdoor air change of 0.5 h⁻¹ and the normal highly airtight nature of new buildings. The guidelines are a basis for designing energy-efficient buildings while maintaining an indoor air quality which provides acceptable comfort and does not impair health.     

137Cs in freshwater fish in Finland since 1986--a statistical analysis with multivariate linear regression models

The accident at the Chernobyl nuclear power plant in 1986 significantly elevated the 137Cs levels of fish in Finnish lakes. About 6200 fish samples from 390 lakes comprising 20 species have been analysed for 137Cs since 1986. The sizes of the lakes varied from a few hectares to about 1000 km2. Activity concentrations of 137Cs in fish still varied widely in 2003, from 16 to 6400 Bq/kg fresh weight. This paper presents the results of statistical analyses with multivariate linear regression models carried out on the empirical data collected since 1986. The statistical analysis resulted in separate models for two time periods describing temporal changes of 137Cs in fish. The explanatory variables were fish species with various feeding habits, the size class of the lake, municipal division, drainage area, time since the deposition and deposition level of the municipality. The calculated values for 137Cs in fish did not differ statistically significantly from the observed values in the validation data. The explanatory variables explained 58% (the first time period) and 72% (the second time period) of the total variability of 137Cs in fish.     

Quantitative determination of volatile organic compounds in indoor dust using gas chromatography-UV spectrometry

A novel technique, gas chromatography-UV spectrometry (GC-UV), was used to quantify volatile organic compounds (VOCs) in settled dust from 389 residences in Sweden. The dust samples were thermally desorbed in an inert atmosphere and evaporated compounds were concentrated by solid phase micro extraction and separated by capillary GC. Eluting compounds were then detected, identified, and quantified using a diode array UV spectrophotometer. Altogether, 28 compounds were quantified in each sample; 24 of these were found in more than 50% of the samples. The compounds found in highest concentrations were saturated aldehydes (C5-C10), furfuryl alcohol, 2,6-di-tert-butyl-4-methylphenol (BHT), 2-furaldehyde, and benzaldehyde. Alkenals were also found, notably 2-butenal (crotonaldehyde), 2-methyl-propenal (methacrolein), hexenal, heptenal, octenal, and nonenal. The concentrations of each of the 28 compounds ranged between two to three orders of magnitude, or even more. These results demonstrate the presence of a number of VOCs in indoor dust, and provide, for the first time, a quantitative determination of these compounds in a larger number of dust samples from residents. The findings also illustrate the potential use of GC-UV for analysing volatile compounds in indoor dust, some of which are potential irritants (to the skin, eyes or respiratory system) if present at higher concentrations. The potential use of GC-UV for improving survey and control of the human exposure to particle-bound irritants and other chemicals is inferred.     

Behaviour and choice of refuge by voles under predation risk

Animals often show a strong antipredatory response when they are exposed to their most deadly predator. In northern vole populations, the least weasel, Mustela nivalis nivalis, is probably the most important predator of voles. Because of its small size and slender body shape, the least weasel is capable of hunting voles in their burrows. However, small voles can potentially escape weasel predation by selecting holes smaller than those weasels can enter. We studied the choice of nest holes and refuges by two species of voles under simulated predation risk. In a laboratory experiment, voles were provided with four nest boxes as refuges, with individually adjusted entrance sizes. When exposed to the odour of a weasel, voles did not choose the smallest opening; they rather seemed to trade full protection for easy and immediate access by choosing the nest box with an intermediate entrance size. When outside the nest at the time when a weasel entered the arena, voles avoided the refuges with the smallest holes. In addition to using refuges on ground level, voles climbed on top of the boxes as an escape reaction, as well as exhibiting a variety of behavioural responses, such as fast running, freezing and sneaking.Communicated by P.A. Bednekoff     

Different escape tactics of two vole species affect the success of the hunting predator, the least weasel

In the ongoing evolutionary arms race between predators and their prey, successful escape from the predator leads to the evolution of improved escape tactics in prey, but also predators become more effective in following and attacking the prey. Antipredatory behavior of prey is considered to be the strongest towards their most dangerous predators. However, prey species can differ both in vulnerability and efficiency of escape to a shared predator. We studied escape reactions of two vole species, the bank vole (Myodes glareolus) and the field vole (Microtus agrestis), under a simulated predation risk of the least weasel (Mustela nivalis nivalis). We conducted a laboratory experiment where a vole was given a possibility to escape from a weasel by fleeing to a horizontal tunnel or climbing the tree. Subsequently to the vole escape decision, we released a weasel to the same tunnel system to test how the weasel succeeded in following the vole. Weasel presence changed the behavior of voles as especially bank voles escaped by climbing. Instead, the majority of field voles fled into the ground-layer tunnel. The different escape tactics of the voles affected the success of the weasel, because climbing voles were less often successfully followed. We suggest that the difference in escape tactics has evolved as an adaptation to different habitats; meadow-exploiting field voles using ground-level escape while bank voles living in three-dimensional forest habitat frequently use arboreal escape tactics. This is likely to lead to different habitat-dependent vulnerabilities to predation in Microtus and Myodes vole species.     

From interference to predation: type and effects of direct interspecific interactions of small mammals

Indirect exploitative competition, direct interference and predation are important interactions affecting species coexistence. These interaction types may overlap and vary with the season and life-history state of individuals. We studied effects of competition and potential nest predation by common shrews (Sorex araneus) on lactating bank voles (Myodes glareolus) in two seasons. The species coexist and may interact aggressively. Additionally, shrews can prey on nestling voles. We studied bank vole mothers’ spatial and temporal adaptations to shrew presence during summer and autumn. Further, we focused on fitness costs, e.g. decreased offspring survival, which bank voles may experience in the presence of shrews. In summer, interference with shrews decreased the voles’ home ranges and they spent more time outside the nest, but there were no effects on offspring survival. In autumn, we found decreased offspring survival in enclosures with shrews, potentially due to nest predation by shrews or by increased competition between species. Our results indicate a shift between interaction types depending on seasonal constraints. In summer, voles and shrews seem to interact mainly by interference, whereas resource competition and/or nest predation by shrews gain importance in autumn. Different food availability, changing environmental conditions and the energetic constraints in voles and shrews later in the year may be the reasons for the varying combinations of interaction types and their increasing effects on the inclusive fitness of bank voles. Our study provides evidence for the need of studies combining life history with behavioural measurements and seasonal constraints.     

Is the antipredatory response in behaviour reflected in stress measured in faecal corticosteroids in a small rodent?

Predation risk has been shown to alter various behaviours in prey. Risk alters activity, habitat use and foraging, and weight decrease might be a consequence of that. In mammals, studies on physiological measures affected by risk of predation, other than weight, are rare. We studied in two separate laboratory experiments foraging, hoarding behaviour and expression of stress measured non-invasively from the faeces in the bank vole (Clethrionomys glareolus), a common boreal rodent. Voles were exposed to predation risk using odours of the least weasels (Mustela nivalis nivalis). Distilled water served as control. In the first experiment, we found that foraging effort, measured as sunflower seeds taken from seed trays filled with sand, was significantly lower in trays scented with weasel odour. Both immediate consumption of seeds and hoarding were affected negatively by the weasel odour. Females hoarded significantly more than males in autumn. In the second experiment, the negative effect of weasel odour on foraging was consistent over a 3-day experiment, but the strongest effect was observed in the first night. Foraging increased over the time of the experiment, which might reflect either energetic compensation during a longer period of risk, predicted in the predation risk allocation hypothesis, or habituation to the odour-simulated risk. Despite decreased foraging under predation risk, stress measured as corticosteroid metabolite concentration in vole faeces was not affected by the weasel odour treatment. In conclusion, we were able to verify predation-risk-mediated changes in the foraging effort of bank voles but no physiological stress response was measured non-invasively, probably due to great individual variation in secretion of stress hormones.