Otso Huitu

Natural Resources Institute Finland (Luke)

Anthropogenic changes to land use drive concomitant changes in biodiversity, including that of the soil microbiota. However, it is not clear how increasing intensity of human disturbance is reflected in the soil microbial communities. To address this issue, we used amplicon sequencing to quantify the microbiota (bacteria and fungi) in the soil of f...

Climate change is a pervasive threat to biodiversity. While range shifts are a known consequence of climate warming contributing to regional community change, less is known about how species’ positions shift within their climatic niches. Furthermore, whether the relative importance of different climatic variables prompting such shifts varies with c...

In Finland, free-ranging Eurasian lynx (Lynx lynx) population has grown from 30–40 individuals to 2800 individuals since the species became partly protected in 1962. Changes in host population size are known to have an impact on host-parasite dynamics, and the Eurasian lynx population in Finland provides a unique opportunity for studying the potent...

There has been a significant increase in the number of reported human cryptosporidiosis cases in recent years. The aim of this study is to estimate the prevalence of Cryptosporidium spp. in wild rodents and shrews, and investigate the species and genotype distribution to assess zoonotic risk. Partial 18S rRNA gene nested-PCR reveals that 36.8, 53.9...

The most common method for rodent control worldwide is the use of anticoagulant rodenticides (ARs), which block the vitamin K cycle and thus cause death by haemorrhage. First-generation anticoagulant rodenticides (FGARs) were introduced into the pest control already in the 1940s and some of them are still in use. Second-generation anticoagulant rod...

Most small rodent populations in the world have fascinating population dynamics. In the northern hemisphere, voles and lemmings tend to show population cycles with regular fluctuations in numbers. In the southern hemisphere, small rodents tend to have large amplitude outbreaks with less regular intervals. In the light of vast research and debate ov...

Authors would like to correct error in affiliation in the original publication of the article.

Small mammals are known to carry Campylobacter spp.; however, little is known about the genotypes and their role in human infections. We studied intestinal content from small wild mammals collected in their natural habitats in Finland in 2010–2017, and in close proximity to 40 pig or cattle farms in 2017. The animals were trapped using traditional...

Climatic conditions, trophic links between species and dispersal may induce spatial synchrony in population fluctuations. Spatial synchrony increases the extinction risk of populations and, thus, it is important to understand how synchrony-inducing mechanisms affect populations already threatened by habitat loss and climate change. For many species...

Number of tick-borne encephalitis (TBE) cases has increased and new foci have emerged in Finland during the last decade. We evaluated risk for locally acquired TBE in the capital region inhabited by 1.2 million people. We screened ticks and small mammals from probable places of TBE virus (TBEV) transmission and places without reported circulation....

Background: There are an increasing number of geo-coded information streams available which could improve public health surveillance accuracy and efficiency when properly integrated. Specifically, for zoonotic diseases, knowledge of spatial and temporal patterns of animal host distribution can be used to raise awareness of human risk and enhance e...

Competing species and predators can alter the habitat use of animals but both factors are rarely simultaneously controlled for. We studied in experimental enclosures how closely related species, the sibling vole ( Microtus levis Miller, 1908) and the field vole ( M. agrestis L., 1761), adjust their habitat use when facing either the competing speci...

Browsing effects of voles on plants can be mitigated by means of non-lethal predation, i.e. by subjecting voles to predator cues. Earlier studies largely focused on mammalian olfactory cues, whereas here we exposed Microtus voles to owl calls to examine whether the introduced predation risk reduces browsing on tree seedlings (silver birch, Scots pi...

Hantaviruses have co-existed with their hosts for millions of years. Seewis virus (SWSV), a soricomorph-borne hantavirus, is widespread in Eurasia, ranging from Central Siberia to Western Europe. To gain insight into the phylogeography and evolutionary history of SWSV in Finland, lung tissue samples of 225 common shrews (Sorex araneus) trapped from...

Oikos Finland 2017

Trade-offs in the allocation of finite-energy resources among immunological defences and other physiological processes are believed to influence infection risk and disease severity in food-limited wildlife populations. However, this prediction has received little experimental investigation. Here we test the hypothesis that food limitation impairs t...

Intraguild (IG) predation and interspecific competition may affect the settlement and success of species in their habitats. Using data on forest-dwelling hawks from Finland, we addressed the impact of an IG predator, the northern goshawk Accipiter gentilis (goshawk), on the breeding of an IG prey, the common buzzard Buteo buteo. We hypothesized tha...

Arvicolines are susceptible to the development of fatty liver during short-term fasting. We examined the potential role of de novo lipogenesis (DNL) (i) in the development of fasting-induced fatty liver and (ii) during a population cycle by measuring the mRNA expression of acetyl-CoA carboxylase-1 (ACC1) and fatty acid synthase (FAS). Laboratory vo...

Trade-offs in the allocation of finite-energy resources among immunological defences and other physiological processes are believed to influence infection risk and disease severity in food-limited wildlife populations. However, this prediction has received little experimental investigation. Here we test the hypothesis that food limitation impairs t...

Trade-offs in the allocation of finite-energy resources among immunological defences and other physiological processes are believed to influence infection risk and disease severity in food-limited wildlife populations. However, this prediction has received little experimental investigation. Here we test the hypothesis that food limitation impairs t...

While pathogens are often assumed to limit the growth of wildlife populations, experimental evidence for their effects is rare. A lack of food resources has been suggested to enhance the negative effects of pathogen infection on host populations, but this theory has received little investigation. We conducted a replicated two-factor enclosure exper...

We studied the incidence of reported tularaemia by year and region and the prevalence of antibodies against Francisella tularensis in the adult general population in Finland. Moreover, we assessed the cor- relation between vole population cycles and human tularaemia outbreaks. The seroprevalence study made use of serum samples from a nationwide pop...

The cyclic population dynamics of vole and predator communities is a key phenomenon in northern ecosystems, and it appears to be influenced by climate change. Reports of collapsing rodent cycles have attributed the changes to warmer winters, which weaken the interaction between voles and their specialist subnivean predators. Using population data c...

Processes limiting the growth of cyclic vole populations have stimulated considerable research and debate over several decades. In Fennoscandia, the peak density of cyclic vole populations occurs in fall, and is followed by a severe winter decline. Food availability and intestinal parasites have been demonstrated to independently and synergisticall...

Tularemia outbreaks in humans have been linked to fluctuations in rodent population density, but the mode of bacterial maintenance in nature is unclear. Here we report on an experiment to investigate the pathogenesis of Francisella tularensis infection in wild rodents, and thereby assess their potential to spread the bacterium. We infected 20 field...

Population densities of forest defoliating insects may be regulated by small mammal predation on the pupae. When outbreaks do occur, they often coincide with warm, dry weather and at barren forest sites. A proposed reason for this is that weather and habitat affect small mammal population density (numerical response) and hence pupal predation. We p...

Grasses have been considered to primarily employ tolerance in lieu of defense in mitigating damage caused by herbivory. Yet a number of mechanisms have been identified in grasses, which may deter feeding by grazers. These include enhanced silicon uptake, hosting of toxin-producing endophytic fungi and induction of secondary metabolites. While these...

To devise effective conservation actions, it is important to know which factors are associated with the population parameters of a declining population. Using mark–recapture methods, we estimated the annual population size, growth rate and survival probability of an ear-tagged flying squirrel population over a 15-year period in a 4,500 ha study are...

Abstract In northern Europe, rodent populations display cyclic density fluctuations that can be correlated with the human incidence of zoonotic diseases they spread. During density peaks, field voles (Microtus agrestis) become one of the most abundant rodent species in northern Europe, yet little is known of the viruses they host. We screened 709 f...

Marked variation occurs in both seasonal and multiannual population density peaks of northern European small mammal species, including voles. The availability of dietary proteins is a key factor limiting the population growth of herbivore species. The objective of this study is to investigate the degree to which protein availability influences the...

Abstract Francisella tularensis is a highly virulent intracellular bacterium causing the zoonotic disease tularemia. It recurrently causes human and animal outbreaks in northern Europe, including Finland. Although F. tularensis infects several mammal species, only rodents and lagomorphs seem to have importance in its ecology. Peak densities of rode...

Virus host-switches have resulted in the emergence of numerous epidemic (including HIV, Wolfe et al. 2007) and epizootic diseases (such as Influenza A virus, Taubenberger and Kash 2010). Spillover is an obligatory first step to a pathogen host-switch (Parish et al. 2008), which is believed to occur far more frequently than sustained transmission wi...

Field voles (Microtus agrestis) cause severe damage to young Norway spruce (Picea abies) plantations during wintertime in Fennoscandia. We experimentally investigated vole preference for winter-dormant, naturally regenerated seedlings; spring-planted seedlings; or autumn-planted seedlings; and how preference corresponds with seedling chemistry. Vol...

The negative impacts of mammalian herbivores on plants have been studied quite extensively, but typically with only a single herbivore species at a time. We conducted a novel comparison of the browsing effects of voles, hares and cervids upon the growth and survival of boreal tree seedlings. This was done by excluding varying assemblages of these k...

The giant panda (Ailuropoda melanoleuca), one of the most threatened mammalian species in the world, has adapted to herbivorous diet consisting mainly of bamboo (Poaceae: Bambusoidea). The most acute threats to the survival of the giant panda are habitat loss and fragmentation. However, changes in habitat may influence also the quality of giant pan...

Aim: Macroecological patterns have mainly been depicted as atemporal, with existing research covering only short time periods. One fundamental pattern in macroecology is the interspecific relationship between local abundance and regional range size, which is generally considered to be positively linear. Here, we examine structural details of the re...

Cycling in Unison Many small mammals, especially voles, display semi-regular cycles of population boom and bust. Given the fundamental importance of small mammals as basal consumers and prey, such cycles can have cascading effects in trophic food webs. Cornulier et al. (p. 63 ) collated raw data from vole populations across Europe collected over th...

Sex allocation theory in vertebrates has greatly benefited from the recent advances in studies on the physiological mechanisms of birth sex ratio variation (e.g., maternal glucose, stress, and testosterone levels). The same physiological mechanisms may, however, also mediate permanent sex-specific effects on individuals after birth. Together with b...

Voles of the genera Microtus and Myodes are widespread and among the most abundant of small mammal species in the boreal zone of the Northern Hemisphere. They are keystone herbivore species in northern ecosystems, and they have profound impacts on both higher and lower trophic levels. Voles are also major silvicultural pests, damaging millions of t...

Small rodents are key species in many ecosystems. In boreal and subarctic environments, their importance is heightened by pronounced multiannual population cycles. Alarmingly, the previously regular rodent cycles appear to be collapsing simultaneously in many areas. Climate change, particularly decreasing snow quality or quantity in winter, is hypo...

This study tested whether the endophyte-promoted competitive superiority of forage grass can be used in biological weed control. Feasibility of endophytes in weed control was tested by manipulating endophyte colonization of meadow fescue (Scherodonus pratensis ex. Lolium pratense and Festuca pratensis) in three experiments. First, species richness,...

The gene expression and induction of cytochrome P450 (CYP)-enzymes following 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) peroral administration was studied in the livers of two wild vole species--the bank vole (Myodes glareolus) and the field vole (Microtus agrestis). The dioxin-sensitive C57BL/6 mouse was used as a reference. Doses of 0.05, 0.5, 5....

The ongoing climate change has improved our understanding of how climate affects the reproduction of animals. However, the interaction between food availability and climate on breeding has rarely been examined. While it has been shown that breeding of boreal birds of prey is first and foremost determined by prey abundance, little information exists...

Plant-associated micro-organisms such as mycotoxin-producing endophytes commonly have direct negative effects on herbivores. These effects may be carried over to natural enemies of the herbivores, but this has been rarely explored. We examined how feeding on Neotyphodium endophyte infected (E+) and endophyte free (E-) meadow ryegrass (Scherodonus p...

The steroid environment encountered by a foetus can strongly affect its post-natal physiology and behaviour. It has been proposed that steroid concentrations experienced in utero could be estimated from adults by measuring their second-to-fourth digit length ratio (2D:4D). However, there is still little direct evidence that intra-uterine steroid le...

Large predators may affect the hunting efficiency of smaller ones directly by decreasing their numbers, or indirectly by altering their behaviour. Either way this may have positive effects on the density of shared prey. Using large outdoor enclosures, we experimentally studied whether the presence of the Tengmalm's owl Aegolius funereus affects the...

The ratio of second-to-fourth digit length (2D/4D) has been suggested to be a useful adult age marker of intrauterine exposure to steroids because it should be sexually dimorphic and fixed already in utero. Numerous studies mainly on humans have supported this conclusion, but it is yet unclear how well this applies to other vertebrates. This inform...

Voles inflict damage to silviculture by debarking or severing tree seedlings. The large-scale impacts of vole damage to silviculture, both in terms of severity and financial losses are, however, poorly known. In autumn 2005, cyclically fluctuating vole populations were at their highest in Finland for over 15 years, which led to extensive damage to...

The proximate physiological mechanisms producing the parental ability to vary offspring sex ratio in many vertebrates remain elusive. Recently, high concentrations of maternal testosterone and glucose and low concentrations of maternal corticosterone have been suggested to explain male bias in offspring sex ratio. We examined how these factors affe...

Fungal endophytes of grasses are known to benefit their hosts directly by increasing resistance to herbivores through mycotoxins. We propose and test assumptions of a novel hypothesis according to which fungal endophytes of grasses may benefit their hosts also indirectly by increasing the conspicuousness of a mammalian herbivore, the field vole (Mi...

Small mammal populations often exhibit large-scale spatial synchrony, which is purportedly caused by stochastic weather-related environmental perturbations, predation or dispersal. To elucidate the relative synchronizing effects of environmental perturbations from those of dispersal movements of small mammalian prey or their predators, we investiga...

Interspecific competition is usually understood as different species competing directly with each other for limited resources. However, predators can alter such competitive interactions substantially. Predation can promote the coexistence of species in a situation where it would otherwise be impossible, for example if a tradeoff between the competi...

Lack of food resources has been suggested as a factor which limits the growth of cyclic vole populations. During peak phases of the cycle, vole population growth typically ceases during late autumn or early winter, and is followed by a decrease in density over the winter. To investigate whether this decrease is due to increased mortality induced by...

Interspecific competition is assumed to generate negative effects on coexisting species, possibly including slower population growth and lower survival. The field vole (Microtus agrestis) and the sibling vole (M. rossiaemeridionalis) are sympatric close relatives which compete for similar resources. Previous non-experimental studies suggest that th...

Endophytes are known to increase the resistance of their host plant to voles directly through reduced palatability

Many species of forest lepidopterans exhibit regular population cycles, which culminate in outbreak densities at approximately ten-year intervals. Population peaks and mass outbreaks typically occur synchronously and may lead to extensive forest damages over large geographic areas. Here, we report patterns of spatial synchrony among cyclic autumnal...

It is generally accepted that predation by wolves Canis lupus is one of the major factors limiting densities of woodland caribou Rangifer tarandus caribou in North America. Conversely, little is known about the role of European wild forest reindeer R. t. fennicus as wolf prey, or about the influence of wolf predation on populations of this rare sub...

Three mechanisms have been proposed to induce spatial synchrony in fluctuations of small mammal populations: climate-related environmental effects, predation and dispersal. We conducted a field experiment in western Finland to evaluate the relative roles of these mechanisms in inducing spatial synchrony among cyclic populations of field voles Micro...

Comprehensive analyses of long-term (1977-2003) small-mammal abundance data from western Finland showed that populations of Microtus voles (field voles M. agrestis and sibling voles M. rossiaemeridionalis) voles, bank (Clethrionomys glareolus) and common shrews (Sorex araneus) fluctuated synchronously in 3 year population cycles. Time-series analys...