Jan Zouhar

Differences in alarm calls of juvenile and adult European ground squirrels (Spermophilus citellus): Findings on permanently marked animals from a semi-natural enclosure

The European ground squirrel (Spermophilus citellus) emits alarm calls that warn conspecifics of potential danger. Although it has been observed that inexperienced juveniles of this species emit alarm calls that sound similar to those of adults, studies focusing on juvenile alarm calls are lacking. We analyzed the acoustic structure of alarm calls emitted by six permanently marked European ground squirrels living in a semi-natural enclosure when they were juveniles and after 1 year as adults. We found that the acoustic structure of the juvenile alarm calls was significantly different from those of adults and that the alarm calls underwent nearly the same changes in all studied individuals. All juveniles emitted alarm calls consisting of one element with almost constant frequency, but their alarm calls included a second frequency-modulated element after their first hibernation as adults. Our data show that the duration of the first element is significantly shorter in adults than in juveniles. Additionally, the frequency of the first element is significantly higher in adults than in juveniles. Similar to previous findings in other Palearctic ground squirrel species, our data are inconsistent with the assumption that juvenile mammals emit vocalizations with higher fundamental frequencies than adults. However, our results do not support the previously suggested hypothesis that juvenile ground squirrels conceal information regarding their age in their alarm calls because we found significant differences in alarm calls of juveniles and adults.

Numbers of wintering waterbirds in the Czech Republic: long-term and spatial-scale approaches to assess population size

Capsule Two nationwide monitoring schemes, the International Waterbird Census (IWC) and Atlas of Wintering Birds (AWB), provide comparable estimates of national population sizes of wintering waterbirds. Differences between these estimates for several species can be explained by differences in their migratory strategy. Aims We tested whether species-specific variables, i.e. the total numbers, distribution and migration strategy affected the accuracy of wintering population estimates provided by two different monitoring schemes, the IWC and AWB. Methods Estimates of the numbers of 81 waterbird species are compared, using data from IWC (mid-January) and AWB (December, January and February) in the Czech Republic between 1982 and 1985. Log-linear Poisson regression analysis was used to estimate missing IWC data from long-term IWC data series (1966–2013) using Trends and Indices for Monitoring data software. A series of generalized linear models was estimated to analyse the effect of species-specific variables on the presence of overlap between IWC and AWB national population estimates. Results The range of numbers recorded by IWC data overlap the range of AWB numbers in 22 of the 53 investigated species recorded by both monitoring schemes. Numbers of most other species based on the IWC counts were lower when compared with those generated from AWB data and included several widespread species, e.g. White-tailed Eagle Haliaeetus albicilla and White-throated Dipper Cinclus cinclus. In contrast, population size estimates based on IWC counts were higher than those generated from AWB estimates for one species, the Ferruginous Duck Aythya nyroca. The differences between IWC and AWB estimates were significantly higher in late-departing and early-arriving migrants. There was no effect of species distribution and population size. Conclusions Based on a single-country data sample, we support the relevance of the IWC Census methodology to produce estimates of wintering waterbird numbers and to calculate 1% thresholds for waterbird species, which we use to indicate nationally important wetland sites for future conservation and protection in the Czech Republic.

Long-Term Changes in Habitat Selection of Wintering Waterbirds: High Importance of Cold Weather Refuge Sites

Abstract. Recent studies showed that climate changes shape species distribution and could cause range shifts in the flyway level of the species. Here, we demonstrated changes in species habitat selection as a response to weather severity in twelve most abundant wintering waterbird species with prevailing increase in numbers during three investigated periods (1972–1978, 1987–1993 and 2003–2009). We used wintering waterbird counts from 93 sites throughout the Czech Republic from mid-January term as the coldest period of winter when the effect of thermoregulation on wintering waterbirds distribution is most apparent. We recorded no significant changes in weather severity in three investigated periods in our study area, and hence we considered the effect of preference of cold weather refuge sites, i.e. habitats which can reduce negative effect of cold weather (running waters, urban area and extensive water surface area). We found prevailing effect of weather severity in the first period what may show thermoregulatory effects being expressed by weather severity on species habitat selection in the next period in six of the twelve investigated species (Mute Swan Cygnus olor, Common Pochard Aythya ferina, Tufted Duck Aythya fuligula, Little Grebe Tachybaptus ruficollis, Common Moorhen Gallinula chloropus and Common Coot Fulica atra). In the face of recent climate change and in spite of the increasing importance of wetlands in the Czech Republic for wintering waterbirds, the suitability of these sites for wintering is likely temperature-dependent. Thus, the preference of cold weather refuges reducing the effect of winter harshness becomes important in individual species.

Resting-associated vocalization emitted by captive Asian house shrews (Suncus murinus): acoustic structure and variability in an unusual mammalian vocalization.

Shrews have rich vocal repertoires that include vocalizations within the human audible frequency range and ultrasonic vocalizations. Here, we recorded and analyzed in detail the acoustic structure of a vocalization with unclear functional significance that was spontaneously produced by 15 adult, captive Asian house shrews (Suncus murinus) while they were lying motionless and resting in their nests. This vocalization was usually emitted repeatedly in a long series with regular intervals. It showed some structural variability; however, the shrews most frequently emitted a tonal, low-frequency vocalization with minimal frequency modulation and a low, non-vocal click that was clearly noticeable at its beginning. There was no effect of sex, but the acoustic structure of the analyzed vocalizations differed significantly between individual shrews. The encoded individuality was low, but it cannot be excluded that this individuality would allow discrimination of family members, i.e., a male and female with their young, collectively resting in a common nest. The question remains whether the Asian house shrews indeed perceive the presence of their mates, parents or young resting in a common nest via the resting-associated vocalization and whether they use it to discriminate among their family members. Additional studies are needed to explain the possible functional significance of resting-associated vocalizations emitted by captive Asian house shrews. Our study highlights that the acoustic communication of shrews is a relatively understudied topic, particularly considering that they are highly vocal mammals.

The Effect of Direct Democracy on Turnout: Voter Mobilization or Participatory Momentum?

Does direct democracy lead to increased electoral turnout? Research in the United States has demonstrated this effect and proposed two reasons for it: (1) the process of being involved in direct political participation may educate citizens and lead to their increased long-term political engagement (this explanation draws on the theory of participatory democracy) and/or (2) underlying issues and competitive campaigning draw public interest and cause higher turnout, although this effect is election-specific and short term. Recent empirical findings overwhelmingly favor the latter hypothesis although both mechanisms seem to apply. However, research on this topic is made difficult by the fact that direct democracy and elections take place simultaneously in the United States, which makes it hard to disentangle the effects of each. We present a study from the Czech Republic where direct democracy is not tied to elections. We analyze the effects of local/municipality direct democracy and demonstrate that it leads to increased turnout in upcoming local and national elections. We demonstrate a strong effect sparked by competitive direct democracy campaigns as well as a relatively weak long-term institutional effect of direct democracy.

PQ oligopoly, proportional rationing, and randomly ordered consumers

In a PQ oligopoly, firms pick prices and quantities simultaneously, and unlike with the traditional Cournot and Bertrand models, market clearing is not imposed. It is thus necessary to specify the rationing rule. Proportional rationing is one of the popular choices, often justified through a notion of randomly ordered consumers with varied reservation prices. However, such a setting would render firm-specific demand a random variable, a fact overlooked in existing models. In the paper, we (1) formalise the notion of randomly ordered consumers into a new stochastic version of the proportional rationing scheme, (2) derive the probabilistic properties of firm-specific demand under this new scheme, and (3) show that the results of the stochastic and deterministic versions are not entirely consistent.

Equilibrium dynamics of European pre-industrial populations: the evidence of carrying capacity in human agricultural societies

Human populations tend to grow steadily, because of the ability of people to make innovations, and thus overcome and extend the limits imposed by natural resources. It is therefore questionable whether traditional concepts of population ecology, including environmental carrying capacity, can be applied to human societies. The existence of carrying capacity cannot be simply inferred from population time-series, but it can be indicated by the tendency of populations to return to a previous state after a disturbance. So far only indirect evidence at a coarse-grained scale has indicated the historical existence of human carrying capacity. We analysed unique historical population data on 88 settlements before and after the Thirty Years War (1618–1648), one the longest and most destructive conflicts in European history, which reduced the population of Central Europe by 30–50%. The recovery rate of individual settlements after the war was positively correlated with the extent of the disturbance, so that the population size of the settlements after a period of regeneration was similar to the pre-war situation, indicating an equilibrium population size (i.e. carrying capacity). The carrying capacity of individual settlements was positively determined mostly by the fertility of the soil and the area of the cadastre, and negatively by the number of other settlements in the surroundings. Pre-industrial human population sizes were thus probably controlled by negative density dependence mediated by soil fertility, which could not increase due to limited agricultural technologies.

Density-dependent regulation of breeding success in the Red-crested Pochard Netta rufina

ABSTRACT Capsule: Numbers of breeding Red-crested Pochard Netta rufina in the Czech Republic were positively correlated with reproductive success in the previous year, yet annual productivity, declined with increasing numbers of females at the beginning of the breeding season, suggesting local limiting factors on this population. Aims: To test the hypothesis that long-term increases in numbers of a breeding population of Red-crested Pochard Netta rufina can be explained by the productivity (numbers of ducklings fledged) in the previous year. We also test for the potential adverse effect of population size on population productivity in the current year. Methods: Data from 2004 to 2016 from South Bohemia, Czech Republic, were analysed using TRends and Indices for Monitoring Data software to investigate changes in numbers of adults, numbers of females at the start of the breeding season and number of broods produced. Results: There was a significant increase in the numbers of adults and females at the beginning of each breeding season. Numbers of adults in May positively correlated with productivity (numbers of ducklings fledged) in the previous breeding season, but relative productivity (broods per adult female) in the current year was negatively correlated with females abundance at the beginning of the breeding season. Conclusions: The study identifies density-dependent regulation as a factor in the population productivity of Red-crested Pochards using intensively managed fishponds as a breeding ground.

Vocal activity of lesser galagos (Galago spp.) at zoos

Almost nothing is known about the natural vocal behavior of lesser galagos living in zoos. This is perhaps because they are usually kept in nocturnal exhibits separated from the visitors by a transparent and acoustically insulating glass barrier. The aim of the present study was therefore to fill this gap in knowledge of the vocal behavior of lesser galagos from zoos. This knowledge might be beneficial because the vocalizations of these small primates can be used for species determination. We performed a 10-day-long acoustic monitoring of vocal activity in each of seven various groups of Galago senegalensis and G. moholi living at four zoos. We quantitatively evaluated the occurrence of four loud vocalization types present in both species, including the most species-specific advertisement call. We found that qualitative as well as quantitative differences exist in the vocal behavior of the studied groups. We confirmed that the observed vocalization types can be collected from lesser galagos living at zoos, and the success can be increased by selecting larger and more diverse groups. We found two distinct patterns of diel vocal activity in the most vocally active groups. G. senegalensis groups were most vocally active at the beginning and at the end of their activity period, whereas one G. moholi group showed an opposite pattern. The latter is surprising, as it is generally accepted that lesser galagos emit advertisement calls especially at dawn and dusk, i.e., at the beginning and at the end of their diel activity.

A MILP approach to the optimization of banner display strategy to tackle banner blindness

The paper addresses the issue of online advertising efficiency in the context of the “banner blindness” phenomenon. We extend the traditional exposure metric of banner efficiency by allowing the effect of a banner display (exposure effect, EE) to vary depending on the sequence of pages that lead to the display. Within a user session on the given website, we assume that EE differs for a banner carried over from the previous page (low EE), from the case where the banner suddenly appears in a previously unoccupied place (high EE). This assumption implies that a banner’s efficiency can be increased by optimising its placement throughout the website’s structure; to this end, we develop a simple model framework. First, we formalize the efficiency metric based on expected total EE for a representative user, using a Markov chain model estimable from the website’s clickstream data. Next, we formulate the selection of efficient banner placement as a mixed integer linear programming problem. We consider two scenarios: (i) a static one, where banner placement is fixed throughout the day, and (ii) a dynamic one, where banner placement is allowed to vary in different time intervals in order to respond to changes in browsing patterns. Finally, we demonstrate the use of our model on an empiric case study, and analyse the effect of different parameter settings.